From e7ad5d2a422720eeae4a407456a5bfcc64755471 Mon Sep 17 00:00:00 2001
From: Ben Newman <ben@meteor.com>
Date: Sat, 24 Mar 2018 14:22:33 -0400
Subject: [PATCH 01/12] Call files.cp_r with { preserveSymlinks: true } in more
 places.

Now that symlinks can be used to enable selective compilation of
node_modules, it's important to preserve them.
---
 tools/cli/commands.js                   |  6 +++--
 tools/fs/files.js                       | 30 ++++++++++++++++++++++---
 tools/isobuild/builder.js               | 26 +++------------------
 tools/tests/old/test-bundler-assets.js  |  4 +++-
 tools/tests/old/test-bundler-npm.js     |  7 ++++--
 tools/tests/old/test-bundler-options.js |  7 ++++--
 tools/tool-testing/sandbox.js           | 15 +++++++++----
 7 files changed, 58 insertions(+), 37 deletions(-)

diff --git a/tools/cli/commands.js b/tools/cli/commands.js
index 2ae436df5c..5fef22f37f 100644
--- a/tools/cli/commands.js
+++ b/tools/cli/commands.js
@@ -582,7 +582,8 @@ main.registerCommand({
             return contents;
           }
         },
-        ignore: [/^local$/]
+        ignore: [/^local$/],
+        preserveSymlinks: true,
       });
     } catch (err) {
       Console.error("Could not create package: " + err.message);
@@ -750,7 +751,8 @@ main.registerCommand({
         return contents;
       }
     },
-    ignore: toIgnore
+    ignore: toIgnore,
+    preserveSymlinks: true,
   });
 
   // We are actually working with a new meteor project at this point, so
diff --git a/tools/fs/files.js b/tools/fs/files.js
index 260b531ce4..cfc31f92c6 100644
--- a/tools/fs/files.js
+++ b/tools/fs/files.js
@@ -495,7 +495,7 @@ files.cp_r = function(from, to, options = {}) {
   files.mkdir_p(files.pathDirname(to));
 
   if (stat.isSymbolicLink()) {
-    files.symlink(files.readlink(from), to);
+    symlinkWithOverwrite(files.readlink(from), to);
 
   } else {
     // Create the file as readable and writable by everyone, and
@@ -517,6 +517,28 @@ files.cp_r = function(from, to, options = {}) {
   }
 };
 
+// create a symlink, overwriting the target link, file, or directory
+// if it exists
+export function symlinkWithOverwrite(source, target) {
+  try {
+    files.symlink(source, target);
+  } catch (e) {
+    if (e.code === "EEXIST") {
+      // overwrite existing link, file, or directory
+      files.rm_recursive(target);
+      files.symlink(source, target);
+    } else if (e.code === "EPERM" &&
+               process.platform === "win32") {
+      files.rm_recursive(target);
+      // This will work only if source refers to a directory, but that's a
+      // chance worth taking.
+      files.symlink(source, target, "junction");
+    } else {
+      throw e;
+    }
+  }
+}
+
 /**
  * Get every path in a directory recursively, treating symlinks as files
  * @param  {String} dir     The directory to walk, either relative to options.cwd or completely absolute
@@ -1003,7 +1025,9 @@ files.renameDirAlmostAtomically =
     // limitations, we'll resort to copying.
     if (forceCopy) {
       files.rm_recursive(toDir);
-      files.cp_r(fromDir, toDir);
+      files.cp_r(fromDir, toDir, {
+        preserveSymlinks: true,
+      });
     }
 
     // ... and take out the trash.
@@ -1750,7 +1774,7 @@ if (files.isWindowsLikeFilesystem()) {
     }
 
     if (! success) {
-      files.cp_r(from, to);
+      files.cp_r(from, to, { preserveSymlinks: true });
       files.rm_recursive(from);
     }
   };
diff --git a/tools/isobuild/builder.js b/tools/isobuild/builder.js
index fdb5973fba..95482e3e0c 100644
--- a/tools/isobuild/builder.js
+++ b/tools/isobuild/builder.js
@@ -1,6 +1,8 @@
 import assert from "assert";
 import {WatchSet, readAndWatchFile, sha1} from '../fs/watch.js';
-import files from '../fs/files.js';
+import files, {
+  symlinkWithOverwrite,
+} from '../fs/files.js';
 import NpmDiscards from './npm-discards.js';
 import {Profile} from '../tool-env/profile.js';
 import {
@@ -805,28 +807,6 @@ function symlinkIfPossible(source, target) {
   }
 }
 
-// create a symlink, overwriting the target link, file, or directory
-// if it exists
-function symlinkWithOverwrite(source, target) {
-  try {
-    files.symlink(source, target);
-  } catch (e) {
-    if (e.code === "EEXIST") {
-      // overwrite existing link, file, or directory
-      files.rm_recursive(target);
-      files.symlink(source, target);
-    } else if (e.code === "EPERM" &&
-               process.platform === "win32") {
-      files.rm_recursive(target);
-      // This will work only if source refers to a directory, but that's a
-      // chance worth taking.
-      files.symlink(source, target, "junction");
-    } else {
-      throw e;
-    }
-  }
-}
-
 // Wrap slow methods into Profiler calls
 const slowBuilderMethods = [
   "_ensureDirectory",
diff --git a/tools/tests/old/test-bundler-assets.js b/tools/tests/old/test-bundler-assets.js
index 54534c5977..c66d4fad19 100644
--- a/tools/tests/old/test-bundler-assets.js
+++ b/tools/tests/old/test-bundler-assets.js
@@ -23,7 +23,9 @@ var makeProjectContext = function (appName) {
 
   var projectDir = files.mkdtemp("test-bundler-assets");
 
-  files.cp_r(testAppDir, projectDir);
+  files.cp_r(testAppDir, projectDir, {
+    preserveSymlinks: true,
+  });
 
   require("../../cli/default-npm-deps.js").install(projectDir);
 
diff --git a/tools/tests/old/test-bundler-npm.js b/tools/tests/old/test-bundler-npm.js
index 1caf634ad8..a14de5168d 100644
--- a/tools/tests/old/test-bundler-npm.js
+++ b/tools/tests/old/test-bundler-npm.js
@@ -19,8 +19,11 @@ var tmpDir = function () {
 
 var makeProjectContext = function (appName) {
   var projectDir = files.mkdtemp("test-bundler-assets");
-  files.cp_r(files.pathJoin(files.convertToStandardPath(__dirname), appName),
-    projectDir);
+  files.cp_r(
+    files.pathJoin(files.convertToStandardPath(__dirname), appName),
+    projectDir,
+    { preserveSymlinks: true },
+  );
   var projectContext = new projectContextModule.ProjectContext({
     projectDir: projectDir
   });
diff --git a/tools/tests/old/test-bundler-options.js b/tools/tests/old/test-bundler-options.js
index 2482ca4999..c2df92a0cd 100644
--- a/tools/tests/old/test-bundler-options.js
+++ b/tools/tests/old/test-bundler-options.js
@@ -18,8 +18,11 @@ var tmpDir = function () {
 
 var makeProjectContext = function (appName) {
   var projectDir = files.mkdtemp("test-bundler-options");
-  files.cp_r(files.pathJoin(files.convertToStandardPath(__dirname), appName),
-    projectDir);
+  files.cp_r(
+    files.pathJoin(files.convertToStandardPath(__dirname), appName),
+    projectDir,
+    { preserveSymlinks: true },
+  );
   var projectContext = new projectContextModule.ProjectContext({
     projectDir: projectDir
   });
diff --git a/tools/tool-testing/sandbox.js b/tools/tool-testing/sandbox.js
index 6937f0e064..91ca8d83cb 100644
--- a/tools/tool-testing/sandbox.js
+++ b/tools/tool-testing/sandbox.js
@@ -167,9 +167,14 @@ export default class Sandbox {
   createApp(to, template, options) {
     options = options || {};
     const absoluteTo = files.pathJoin(this.cwd, to);
-    files.cp_r(files.pathJoin(
-      files.convertToStandardPath(__dirname), '..', 'tests', 'apps', template),
-        absoluteTo, { ignore: [/^local$/] });
+    const absoluteFrom = files.pathJoin(
+      files.convertToStandardPath(__dirname),
+      '..', 'tests', 'apps', template
+    );
+    files.cp_r(absoluteFrom, absoluteTo, {
+      ignore: [/^local$/],
+      preserveSymlinks: true,
+    });
     // If the test isn't explicitly managing a mock warehouse, ensure that apps
     // run with our release by default.
     if (options.release) {
@@ -222,7 +227,9 @@ export default class Sandbox {
     const packagePath = files.pathJoin(this.cwd, packageDir);
     const templatePackagePath = files.pathJoin(
       files.convertToStandardPath(__dirname), '..', 'tests', 'packages', template);
-    files.cp_r(templatePackagePath, packagePath);
+    files.cp_r(templatePackagePath, packagePath, {
+      preserveSymlinks: true,
+    });
 
     files.readdir(packagePath).forEach((file) => {
       if (file.match(/^package.*\.js$/)) {

From c6c92255e560de954c057d0f8ce9efa40974562a Mon Sep 17 00:00:00 2001
From: Ben Newman <ben@meteor.com>
Date: Sat, 24 Mar 2018 14:42:26 -0400
Subject: [PATCH 02/12] Relax options.from precondition in
 Builder#copyNodeModulesDirectory.

---
 tools/isobuild/builder.js | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/tools/isobuild/builder.js b/tools/isobuild/builder.js
index 95482e3e0c..b9566acf2b 100644
--- a/tools/isobuild/builder.js
+++ b/tools/isobuild/builder.js
@@ -395,7 +395,10 @@ Previous builder: ${previousBuilder.outputPath}, this builder: ${outputPath}`
   // A version of copyDirectory that works better for copying node_modules
   // directories when symlinks are involved.
   copyNodeModulesDirectory(options) {
-    assert.strictEqual(files.pathBasename(options.from), "node_modules");
+    // Although the options.from directory should probably be a
+    // node_modules directory, the only essential precondition here is
+    // that the destination directory is a node_modules directory.
+    // assert.strictEqual(files.pathBasename(options.from), "node_modules");
     assert.strictEqual(files.pathBasename(options.to), "node_modules");
 
     if (options.symlink) {

From 1757a69d8baa1bde52a1d16702ed68f72955836c Mon Sep 17 00:00:00 2001
From: Ben Newman <ben@meteor.com>
Date: Thu, 22 Mar 2018 19:18:56 -0400
Subject: [PATCH 03/12] Generate stubs that call module.useNode() for server
 node_modules.

Once this logic is established, the install.js library will no longer need
to know anything about module.useNode():
https://github.com/benjamn/install/blob/6412f4aabbb44501ad557f578d8ab39f78f22d2c/install.js#L322-L325
---
 tools/isobuild/import-scanner.js | 67 ++++++++++++++++++++------------
 1 file changed, 42 insertions(+), 25 deletions(-)

diff --git a/tools/isobuild/import-scanner.js b/tools/isobuild/import-scanner.js
index 57e8f6642b..377fcccd8f 100644
--- a/tools/isobuild/import-scanner.js
+++ b/tools/isobuild/import-scanner.js
@@ -134,6 +134,18 @@ const IMPORT_SCANNER_CACHE = new LRU({
   }
 });
 
+// Stub used for entry point modules within node_modules directories on
+// the server. These stub modules delegate to native Node evaluation by
+// calling module.useNode() immediately, but it's important that we have
+// something to include in the bundle so that parent modules have
+// something to resolve.
+const useNodeStub = {
+  dataString: "module.useNode();",
+  deps: Object.create(null),
+};
+useNodeStub.data = Buffer.from(useNodeStub.dataString, "utf8");
+useNodeStub.hash = sha1(useNodeStub.data);
+
 export default class ImportScanner {
   constructor({
     name,
@@ -769,12 +781,35 @@ export default class ImportScanner {
 
       info.absModuleId = absModuleId;
 
-      // If the module is not readable, _readModule may return
-      // null. Otherwise it will return an object with .data, .dataString,
-      // and .hash properties.
-      depFile = this._readModule(absImportedPath);
-      if (! depFile) {
-        return;
+      if (! this.isWeb() &&
+          absModuleId.startsWith("/node_modules/")) {
+        // On the server, modules in node_modules directories will be
+        // handled natively by Node, so we just need to generate a stub
+        // module that calls module.useNode(), rather than calling
+        // this._readModule to read the actual module file. Note that
+        // useNodeStub includes an empty .deps property, which will make
+        // this._scanFile(depFile, dynamic) return immediately.
+        depFile = { ...useNodeStub };
+
+        // If optimistic functions care about this file, e.g. because it
+        // resides in a linked npm package, then we should allow it to
+        // be watched even though we are replacing it with a stub that
+        // merely calls module.useNode().
+        if (shouldWatch(absImportedPath)) {
+          this.watchSet.addFile(
+            absImportedPath,
+            optimisticHashOrNull(absImportedPath),
+          );
+        }
+
+      } else {
+        // If the module is not readable, _readModule may return
+        // null. Otherwise it will return an object with .data,
+        // .dataString, and .hash properties.
+        depFile = this._readModule(absImportedPath);
+        if (! depFile) {
+          return;
+        }
       }
 
       depFile.type = "js"; // TODO Is this correct?
@@ -790,25 +825,7 @@ export default class ImportScanner {
       // Append this file to the output array and record its index.
       this._addFile(absImportedPath, depFile);
 
-      // On the server, modules in node_modules directories will be
-      // handled natively by Node, so we don't need to build a
-      // meteorInstall-style bundle beyond the entry-point module.
-      if (! this.isWeb() &&
-          depFile.absModuleId.startsWith("/node_modules/") &&
-          // If optimistic functions care about this file, e.g. because it
-          // resides in a linked npm package, then we should allow it to
-          // be watched by including it in the server bundle by not
-          // returning here. Note that inclusion in the server bundle is
-          // an unnecessary consequence of this logic, since Node will
-          // still evaluate this module natively on the server. What we
-          // really care about is watching the file for changes.
-          ! shouldWatch(absImportedPath)) {
-        // Since we're not going to call this._scanFile(depFile, dynamic)
-        // below, this is our last chance to update depFile.imported.
-        depFile.imported = dynamic ? "dynamic" : true;
-        return;
-      }
-
+      // Recursively scan the module's imported dependencies.
       this._scanFile(depFile, dynamic);
     });
   }

From 0fca4c56aaea8487ce41356dc1b754b8c8f8eaa2 Mon Sep 17 00:00:00 2001
From: Ben Newman <ben@meteor.com>
Date: Fri, 23 Mar 2018 16:38:55 -0400
Subject: [PATCH 04/12] Fix handling of old files in ImportScanner#_addFile.

---
 tools/isobuild/import-scanner.js | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/tools/isobuild/import-scanner.js b/tools/isobuild/import-scanner.js
index 377fcccd8f..cc08aa2546 100644
--- a/tools/isobuild/import-scanner.js
+++ b/tools/isobuild/import-scanner.js
@@ -205,10 +205,12 @@ export default class ImportScanner {
       return file;
     }
 
-    absPath = absPath.toLowerCase();
-    const old = this.absPathToOutputIndex[absPath];
+    const absLowerPath = absPath.toLowerCase();
+
+    if (has(this.absPathToOutputIndex, absLowerPath)) {
+      const old = this.outputFiles[
+        this.absPathToOutputIndex[absLowerPath]];
 
-    if (old) {
       // If the old file is just an empty stub, let the new file take
       // precedence over it.
       if (old.implicit === true) {
@@ -225,7 +227,7 @@ export default class ImportScanner {
       }
 
     } else {
-      this.absPathToOutputIndex[absPath] =
+      this.absPathToOutputIndex[absLowerPath] =
         this.outputFiles.push(file) - 1;
 
       return file;

From ebd84317d8401f718867ae7f78410a6abd6b2c65 Mon Sep 17 00:00:00 2001
From: Ben Newman <ben@meteor.com>
Date: Mon, 26 Mar 2018 11:44:22 -0400
Subject: [PATCH 05/12] Decompose _readDepFile helper from
 ImportScanner#_scanFile.

---
 tools/isobuild/import-scanner.js | 107 ++++++++++++++++---------------
 1 file changed, 56 insertions(+), 51 deletions(-)

diff --git a/tools/isobuild/import-scanner.js b/tools/isobuild/import-scanner.js
index cc08aa2546..9ea636c370 100644
--- a/tools/isobuild/import-scanner.js
+++ b/tools/isobuild/import-scanner.js
@@ -740,11 +740,7 @@ export default class ImportScanner {
          info.dynamic);
 
       const resolved = this._resolve(file, id, dynamic);
-      if (! resolved) {
-        return;
-      }
-
-      const absImportedPath = resolved.path;
+      const absImportedPath = resolved && resolved.path;
       if (! absImportedPath) {
         return;
       }
@@ -775,55 +771,11 @@ export default class ImportScanner {
         return;
       }
 
-      const absModuleId = this._getAbsModuleId(absImportedPath);
-      if (! absModuleId) {
-        // The given path cannot be installed on this architecture.
+      depFile = this._readDepFile(absImportedPath);
+      if (! depFile) {
         return;
       }
 
-      info.absModuleId = absModuleId;
-
-      if (! this.isWeb() &&
-          absModuleId.startsWith("/node_modules/")) {
-        // On the server, modules in node_modules directories will be
-        // handled natively by Node, so we just need to generate a stub
-        // module that calls module.useNode(), rather than calling
-        // this._readModule to read the actual module file. Note that
-        // useNodeStub includes an empty .deps property, which will make
-        // this._scanFile(depFile, dynamic) return immediately.
-        depFile = { ...useNodeStub };
-
-        // If optimistic functions care about this file, e.g. because it
-        // resides in a linked npm package, then we should allow it to
-        // be watched even though we are replacing it with a stub that
-        // merely calls module.useNode().
-        if (shouldWatch(absImportedPath)) {
-          this.watchSet.addFile(
-            absImportedPath,
-            optimisticHashOrNull(absImportedPath),
-          );
-        }
-
-      } else {
-        // If the module is not readable, _readModule may return
-        // null. Otherwise it will return an object with .data,
-        // .dataString, and .hash properties.
-        depFile = this._readModule(absImportedPath);
-        if (! depFile) {
-          return;
-        }
-      }
-
-      depFile.type = "js"; // TODO Is this correct?
-      depFile.sourcePath = pathRelative(this.sourceRoot, absImportedPath);
-      depFile.absModuleId = absModuleId;
-      depFile.servePath = stripLeadingSlash(absModuleId);
-      depFile.lazy = true;
-      // Setting depFile.imported = false is necessary so that
-      // this._scanFile(depFile, dynamic) doesn't think the file has been
-      // scanned already and return immediately.
-      depFile.imported = false;
-
       // Append this file to the output array and record its index.
       this._addFile(absImportedPath, depFile);
 
@@ -908,6 +860,59 @@ export default class ImportScanner {
     return info;
   }
 
+  _readDepFile(absPath) {
+    const absModuleId = this._getAbsModuleId(absPath);
+    if (! absModuleId) {
+      // The given path cannot be installed on this architecture.
+      return null;
+    }
+
+    let depFile = null;
+
+    if (! this.isWeb() &&
+        absModuleId.startsWith("/node_modules/")) {
+      // On the server, modules in node_modules directories will be
+      // handled natively by Node, so we just need to generate a stub
+      // module that calls module.useNode(), rather than calling
+      // this._readModule to read the actual module file. Note that
+      // useNodeStub includes an empty .deps property, which will make
+      // this._scanFile(depFile, dynamic) return immediately.
+      depFile = { ...useNodeStub };
+
+      // If optimistic functions care about this file, e.g. because it
+      // resides in a linked npm package, then we should allow it to
+      // be watched even though we are replacing it with a stub that
+      // merely calls module.useNode().
+      if (shouldWatch(absPath)) {
+        this.watchSet.addFile(
+          absPath,
+          optimisticHashOrNull(absPath),
+        );
+      }
+
+    } else {
+      // If the module is not readable, _readModule may return
+      // null. Otherwise it will return an object with .data,
+      // .dataString, and .hash properties.
+      depFile = this._readModule(absPath);
+      if (! depFile) {
+        return null;
+      }
+    }
+
+    depFile.type = "js"; // TODO Is this correct?
+    depFile.sourcePath = pathRelative(this.sourceRoot, absPath);
+    depFile.absModuleId = absModuleId;
+    depFile.servePath = stripLeadingSlash(absModuleId);
+    depFile.lazy = true;
+    // Setting depFile.imported = false is necessary so that
+    // this._scanFile(depFile, dynamic) doesn't think the file has been
+    // scanned already and return immediately.
+    depFile.imported = false;
+
+    return depFile;
+  }
+
   // Returns an absolute module identifier indicating where to install the
   // given file via meteorInstall. May return undefined if the file should
   // not be installed on the current architecture.

From 9c95b78d9eef55b355219528622f8fbdd017b3e1 Mon Sep 17 00:00:00 2001
From: Ben Newman <ben@meteor.com>
Date: Thu, 22 Mar 2018 22:24:03 -0400
Subject: [PATCH 06/12] Upgrade install.js package to avoid calling
 Module.prototype.useNode.

https://github.com/benjamn/install/commit/f69158f0a1f9fa0bb29db71666997a28f8be2fca
---
 packages/modules-runtime/.npm/package/npm-shrinkwrap.json | 6 +++---
 packages/modules-runtime/package.js                       | 4 ++--
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/packages/modules-runtime/.npm/package/npm-shrinkwrap.json b/packages/modules-runtime/.npm/package/npm-shrinkwrap.json
index cab824928f..d79cb72b6b 100644
--- a/packages/modules-runtime/.npm/package/npm-shrinkwrap.json
+++ b/packages/modules-runtime/.npm/package/npm-shrinkwrap.json
@@ -2,9 +2,9 @@
   "lockfileVersion": 1,
   "dependencies": {
     "install": {
-      "version": "0.10.4",
-      "resolved": "https://registry.npmjs.org/install/-/install-0.10.4.tgz",
-      "integrity": "sha512-+IRyOastuPmLVx9zlVXJoKErSqz1Ma5at9A7S8yfsj3W+Kg95faPoh3bPDtMrZ/grz4PRmXzrswmlzfLlYyLOw=="
+      "version": "0.11.0",
+      "resolved": "https://registry.npmjs.org/install/-/install-0.11.0.tgz",
+      "integrity": "sha512-30UqvWKr/59SStU2/bRye4wT1S3mzjwa0oV+BxusB0neGqhxUrwLlnXDbt6QtIfBxCNWFqg+ARnGNjFj8XuV5A=="
     }
   }
 }
diff --git a/packages/modules-runtime/package.js b/packages/modules-runtime/package.js
index b0bbb12abe..96b9a42582 100644
--- a/packages/modules-runtime/package.js
+++ b/packages/modules-runtime/package.js
@@ -1,13 +1,13 @@
 Package.describe({
   name: "modules-runtime",
-  version: "0.9.2",
+  version: "0.10.0",
   summary: "CommonJS module system",
   git: "https://github.com/benjamn/install",
   documentation: "README.md"
 });
 
 Npm.depends({
-  install: "0.10.4"
+  install: "0.11.0"
 });
 
 Package.onUse(function(api) {

From 970d58409fc2a7b7a78bbc7098aef24c38f1f249 Mon Sep 17 00:00:00 2001
From: Ben Newman <ben@meteor.com>
Date: Thu, 22 Mar 2018 18:52:54 -0400
Subject: [PATCH 07/12] Move realpathOrNull into tools/fs/files.js.

---
 tools/fs/files.js         |  9 +++++++++
 tools/isobuild/bundler.js | 11 +----------
 2 files changed, 10 insertions(+), 10 deletions(-)

diff --git a/tools/fs/files.js b/tools/fs/files.js
index cfc31f92c6..f5286fc165 100644
--- a/tools/fs/files.js
+++ b/tools/fs/files.js
@@ -297,6 +297,15 @@ function statOrNull(path, preserveSymlinks) {
   }
 }
 
+export function realpathOrNull(path) {
+  try {
+    return files.realpath(path);
+  } catch (e) {
+    if (e.code !== "ENOENT") throw e;
+    return null;
+  }
+}
+
 files.rm_recursive_async = (path) => {
   return new Promise((resolve, reject) => {
     rimraf(files.convertToOSPath(path), err => err
diff --git a/tools/isobuild/bundler.js b/tools/isobuild/bundler.js
index 6b84a4a5e5..2cd07f968f 100644
--- a/tools/isobuild/bundler.js
+++ b/tools/isobuild/bundler.js
@@ -482,7 +482,7 @@ export class NodeModulesDirectory {
           return true;
         }
 
-        const real = realpathOrNull(path);
+        const real = files.realpathOrNull(path);
         if (typeof real === "string" &&
             real !== path) {
           // If node_modules/.bin/command is a symlink, determine the
@@ -522,15 +522,6 @@ export class NodeModulesDirectory {
   }
 }
 
-function realpathOrNull(path) {
-  try {
-    return files.realpath(path);
-  } catch (e) {
-    if (e.code !== "ENOENT") throw e;
-    return null;
-  }
-}
-
 ///////////////////////////////////////////////////////////////////////////////
 // File
 ///////////////////////////////////////////////////////////////////////////////

From d35987d9292ee836f1442c65e645990cfbf94c83 Mon Sep 17 00:00:00 2001
From: Ben Newman <ben@meteor.com>
Date: Mon, 26 Mar 2018 12:48:57 -0400
Subject: [PATCH 08/12] Enable selective compilation of node_modules via
 symlinking.

If a package in node_modules needs to be compiled for older browsers,
simply symlink the package directory into your application somewhere, and
then import the package as you normally would.

Because of the symlink, code within the package will be compiled as if it
was part of your application, and any imports that refer to modules in the
package will automatically use the compiled code rather than the raw code
from node_modules.

Note that you can also symlink individual files to make them be compiled
like application modules, rather than linking an entire package directory.

Creating symlinks could be considered a form of configuration, but
otherwise this is a zero-configuration solution to selectively compiling
packages within node_modules, which has been something of a holy grail in
the JavaScript community lately.

https://github.com/meteor/meteor-feature-requests/issues/6
---
 tools/isobuild/import-scanner.js | 135 ++++++++++++++++++++++++++++++-
 1 file changed, 132 insertions(+), 3 deletions(-)

diff --git a/tools/isobuild/import-scanner.js b/tools/isobuild/import-scanner.js
index 9ea636c370..b1163a8fda 100644
--- a/tools/isobuild/import-scanner.js
+++ b/tools/isobuild/import-scanner.js
@@ -18,9 +18,11 @@ import {
   pathNormalize,
   pathBasename,
   pathExtname,
+  pathDirname,
   pathIsAbsolute,
   convertToOSPath,
   convertToPosixPath,
+  realpathOrNull,
 } from "../fs/files.js";
 
 const {
@@ -32,6 +34,7 @@ const {
 import {
   optimisticReadFile,
   optimisticStatOrNull,
+  optimisticLStatOrNull,
   optimisticHashOrNull,
   shouldWatch,
 } from "../fs/optimistic.js";
@@ -163,6 +166,8 @@ export default class ImportScanner {
     this.nodeModulesPaths = nodeModulesPaths;
     this.watchSet = watchSet;
     this.absPathToOutputIndex = Object.create(null);
+    this.realPathToFiles = Object.create(null);
+    this.realPathCache = Object.create(null);
     this.allMissingModules = Object.create(null);
     this.outputFiles = [];
 
@@ -268,11 +273,82 @@ export default class ImportScanner {
         // multiple times with the same sourcePath. #6422
         this._combineFiles(this._getFile(absPath), file);
       }
+
+      this._addFileByRealPath(file, this._realPath(absPath));
     });
 
     return this;
   }
 
+  _addFileByRealPath(file, realPath) {
+    assert.ok(isObject(file));
+    assert.strictEqual(typeof realPath, "string");
+
+    if (! has(this.realPathToFiles, realPath)) {
+      this.realPathToFiles[realPath] = [];
+    }
+
+    const files = this.realPathToFiles[realPath];
+
+    if (files.indexOf(file) < 0) {
+      files.push(file);
+    }
+
+    return file;
+  }
+
+  _getInfoByRealPath(realPath) {
+    assert.strictEqual(typeof realPath, "string");
+    const files = this.realPathToFiles[realPath];
+    if (files && files.length > 0) {
+      const firstFile = files[0];
+      return {
+        data: firstFile.data,
+        dataString: firstFile.dataString,
+        hash: firstFile.hash,
+      };
+    }
+    return null;
+  }
+
+  _realPath(absPath) {
+    if (has(this.realPathCache, absPath)) {
+      return this.realPathCache[absPath];
+    }
+
+    let relativePath = pathRelative(this.sourceRoot, absPath);
+    if (relativePath.startsWith("..")) {
+      // If the absPath is outside this.sourceRoot, assume it's real.
+      return this.realPathCache[absPath] = absPath;
+    }
+
+    let foundSymbolicLink = false;
+
+    while (! foundSymbolicLink) {
+      const testPath = pathJoin(this.sourceRoot, relativePath);
+      if (testPath === this.sourceRoot) {
+        // Don't test the sourceRoot itself.
+        break;
+      }
+
+      const lstat = optimisticLStatOrNull(testPath);
+      if (lstat && lstat.isSymbolicLink()) {
+        foundSymbolicLink = true;
+        break
+      }
+
+      relativePath = pathDirname(relativePath);
+    }
+
+    if (foundSymbolicLink) {
+      // Call the actual realpathOrNull function only if there were any
+      // symlinks involved in the relative path within this.sourceRoot.
+      return this.realPathCache[absPath] = realpathOrNull(absPath);
+    }
+
+    return this.realPathCache[absPath] = absPath;
+  }
+
   // Make sure file.sourcePath is defined, and handle the possibility that
   // file.targetPath differs from file.sourcePath.
   _checkSourceAndTargetPaths(file) {
@@ -552,7 +628,45 @@ export default class ImportScanner {
     });
   }
 
+  _mergeFilesWithSameRealPath() {
+    Object.keys(this.realPathToFiles).forEach(realPath => {
+      const files = this.realPathToFiles[realPath];
+      if (! files || files.length < 2) {
+        return;
+      }
+
+      // We have multiple files that share the same realPath, so we need
+      // to figure out which one should actually contain the data, and
+      // which one(s) should merely be aliases to the data container.
+
+      let container = files[0];
+
+      // Take the first file inside node_modules as the container. If none
+      // found, default to the first file in the list. It's important to
+      // let node_modules files be the containers if possible, since some
+      // npm packages rely on having module IDs that appear to be within a
+      // node_modules directory.
+      files.some(file => {
+        if (file.absModuleId &&
+            file.absModuleId.startsWith("/node_modules/")) {
+          container = file;
+          return true;
+        }
+      });
+
+      // Alias every non-container file to container.absModuleId.
+      files.forEach(file => {
+        if (file !== container) {
+          file.alias = file.alias || {};
+          file.alias.absModuleId = container.absModuleId;
+        }
+      });
+    });
+  }
+
   getOutputFiles() {
+    this._mergeFilesWithSameRealPath();
+
     // Return all installable output files that are either eager or
     // imported (statically or dynamically).
     return this.outputFiles.filter(file => {
@@ -867,10 +981,22 @@ export default class ImportScanner {
       return null;
     }
 
-    let depFile = null;
+    const realPath = this._realPath(absPath);
 
-    if (! this.isWeb() &&
-        absModuleId.startsWith("/node_modules/")) {
+    let depFile = this._getInfoByRealPath(realPath);
+    if (depFile) {
+      // If we already have a file with the same real path, use its data
+      // rather than reading the file again, or generating a stub. This
+      // logic enables selective compilation of node_modules in an elegant
+      // way: just expose the package directory within the application
+      // (outside of node_modules) using a symlink, so that it will be
+      // compiled as application code. When the package is imported from
+      // node_modules, the compiled version will be used instead of the
+      // raw version found in node_modules. See also:
+      // https://github.com/meteor/meteor-feature-requests/issues/6
+
+    } else if (! this.isWeb() &&
+               absModuleId.startsWith("/node_modules/")) {
       // On the server, modules in node_modules directories will be
       // handled natively by Node, so we just need to generate a stub
       // module that calls module.useNode(), rather than calling
@@ -910,6 +1036,8 @@ export default class ImportScanner {
     // scanned already and return immediately.
     depFile.imported = false;
 
+    this._addFileByRealPath(depFile, realPath);
+
     return depFile;
   }
 
@@ -1256,6 +1384,7 @@ each([
   "_findImportedModuleIdentifiers",
   "_getAbsModuleId",
   "_addPkgJsonToOutput",
+  "_realPath",
   "_resolvePkgJsonBrowserAliases",
 ], funcName => {
   ImportScanner.prototype[funcName] = Profile(

From 9401f0d572648ad091cfd3f8ac2048db929b549e Mon Sep 17 00:00:00 2001
From: Ben Newman <ben@meteor.com>
Date: Fri, 23 Mar 2018 12:29:07 -0400
Subject: [PATCH 09/12] Add tests of selective node_modules compilation using
 symlinks.

---
 .../apps/modules/imports/links/acorn/LICENSE  |   19 +
 .../modules/imports/links/acorn/package.json  |   51 +
 .../modules/imports/links/acorn/src/.eslintrc |   33 +
 .../imports/links/acorn/src/bin/.eslintrc     |    6 +
 .../imports/links/acorn/src/bin/acorn.js      |   62 +
 .../imports/links/acorn/src/expression.js     |  909 ++++++++++++++
 .../imports/links/acorn/src/identifier.js     |   87 ++
 .../modules/imports/links/acorn/src/index.js  |   78 ++
 .../imports/links/acorn/src/location.js       |   26 +
 .../imports/links/acorn/src/locutil.js        |   42 +
 .../links/acorn/src/loose/expression.js       |  582 +++++++++
 .../imports/links/acorn/src/loose/index.js    |   47 +
 .../links/acorn/src/loose/parseutil.js        |    1 +
 .../imports/links/acorn/src/loose/state.js    |  170 +++
 .../links/acorn/src/loose/statement.js        |  459 ++++++++
 .../imports/links/acorn/src/loose/tokenize.js |  111 ++
 .../modules/imports/links/acorn/src/lval.js   |  248 ++++
 .../modules/imports/links/acorn/src/node.js   |   50 +
 .../imports/links/acorn/src/options.js        |  127 ++
 .../imports/links/acorn/src/parseutil.js      |  137 +++
 .../modules/imports/links/acorn/src/regexp.js | 1042 +++++++++++++++++
 .../modules/imports/links/acorn/src/scope.js  |   74 ++
 .../modules/imports/links/acorn/src/state.js  |  118 ++
 .../imports/links/acorn/src/statement.js      |  810 +++++++++++++
 .../imports/links/acorn/src/tokencontext.js   |  148 +++
 .../imports/links/acorn/src/tokenize.js       |  698 +++++++++++
 .../imports/links/acorn/src/tokentype.js      |  148 +++
 .../links/acorn/src/unicode-property-data.js  |  463 ++++++++
 .../modules/imports/links/acorn/src/util.js   |   11 +
 .../imports/links/acorn/src/walk/index.js     |  370 ++++++
 .../imports/links/acorn/src/whitespace.js     |   13 +
 .../modules/imports/links/immutable-tuple     |    1 +
 .../apps/modules/imports/links/lodash-es      |    1 +
 tools/tests/apps/modules/package-lock.json    |   13 +
 tools/tests/apps/modules/package.json         |    3 +
 tools/tests/apps/modules/tests.js             |   38 +
 36 files changed, 7196 insertions(+)
 create mode 100644 tools/tests/apps/modules/imports/links/acorn/LICENSE
 create mode 100644 tools/tests/apps/modules/imports/links/acorn/package.json
 create mode 100644 tools/tests/apps/modules/imports/links/acorn/src/.eslintrc
 create mode 100644 tools/tests/apps/modules/imports/links/acorn/src/bin/.eslintrc
 create mode 100644 tools/tests/apps/modules/imports/links/acorn/src/bin/acorn.js
 create mode 100644 tools/tests/apps/modules/imports/links/acorn/src/expression.js
 create mode 100644 tools/tests/apps/modules/imports/links/acorn/src/identifier.js
 create mode 100644 tools/tests/apps/modules/imports/links/acorn/src/index.js
 create mode 100644 tools/tests/apps/modules/imports/links/acorn/src/location.js
 create mode 100644 tools/tests/apps/modules/imports/links/acorn/src/locutil.js
 create mode 100644 tools/tests/apps/modules/imports/links/acorn/src/loose/expression.js
 create mode 100644 tools/tests/apps/modules/imports/links/acorn/src/loose/index.js
 create mode 100644 tools/tests/apps/modules/imports/links/acorn/src/loose/parseutil.js
 create mode 100644 tools/tests/apps/modules/imports/links/acorn/src/loose/state.js
 create mode 100644 tools/tests/apps/modules/imports/links/acorn/src/loose/statement.js
 create mode 100644 tools/tests/apps/modules/imports/links/acorn/src/loose/tokenize.js
 create mode 100644 tools/tests/apps/modules/imports/links/acorn/src/lval.js
 create mode 100644 tools/tests/apps/modules/imports/links/acorn/src/node.js
 create mode 100644 tools/tests/apps/modules/imports/links/acorn/src/options.js
 create mode 100644 tools/tests/apps/modules/imports/links/acorn/src/parseutil.js
 create mode 100644 tools/tests/apps/modules/imports/links/acorn/src/regexp.js
 create mode 100644 tools/tests/apps/modules/imports/links/acorn/src/scope.js
 create mode 100644 tools/tests/apps/modules/imports/links/acorn/src/state.js
 create mode 100644 tools/tests/apps/modules/imports/links/acorn/src/statement.js
 create mode 100644 tools/tests/apps/modules/imports/links/acorn/src/tokencontext.js
 create mode 100644 tools/tests/apps/modules/imports/links/acorn/src/tokenize.js
 create mode 100644 tools/tests/apps/modules/imports/links/acorn/src/tokentype.js
 create mode 100644 tools/tests/apps/modules/imports/links/acorn/src/unicode-property-data.js
 create mode 100644 tools/tests/apps/modules/imports/links/acorn/src/util.js
 create mode 100644 tools/tests/apps/modules/imports/links/acorn/src/walk/index.js
 create mode 100644 tools/tests/apps/modules/imports/links/acorn/src/whitespace.js
 create mode 120000 tools/tests/apps/modules/imports/links/immutable-tuple
 create mode 120000 tools/tests/apps/modules/imports/links/lodash-es

diff --git a/tools/tests/apps/modules/imports/links/acorn/LICENSE b/tools/tests/apps/modules/imports/links/acorn/LICENSE
new file mode 100644
index 0000000000..2c0632b6a7
--- /dev/null
+++ b/tools/tests/apps/modules/imports/links/acorn/LICENSE
@@ -0,0 +1,19 @@
+Copyright (C) 2012-2018 by various contributors (see AUTHORS)
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.
diff --git a/tools/tests/apps/modules/imports/links/acorn/package.json b/tools/tests/apps/modules/imports/links/acorn/package.json
new file mode 100644
index 0000000000..1b47c365cc
--- /dev/null
+++ b/tools/tests/apps/modules/imports/links/acorn/package.json
@@ -0,0 +1,51 @@
+{
+  "name": "acorn",
+  "description": "ECMAScript parser",
+  "homepage": "https://github.com/acornjs/acorn",
+  "main": "src/index.js",
+  "version": "5.5.3",
+  "engines": {
+    "node": ">=0.4.0"
+  },
+  "maintainers": [
+    {
+      "name": "Marijn Haverbeke",
+      "email": "marijnh@gmail.com",
+      "web": "http://marijnhaverbeke.nl"
+    },
+    {
+      "name": "Ingvar Stepanyan",
+      "email": "me@rreverser.com",
+      "web": "http://rreverser.com/"
+    }
+  ],
+  "repository": {
+    "type": "git",
+    "url": "https://github.com/acornjs/acorn.git"
+  },
+  "license": "MIT",
+  "scripts": {
+    "prepare": "npm test",
+    "test": "node test/run.js && node test/lint.js",
+    "pretest": "npm run build:main && npm run build:loose",
+    "test:test262": "node bin/run_test262.js",
+    "build": "npm run build:main && npm run build:walk && npm run build:loose && npm run build:bin",
+    "build:main": "rollup -c rollup/config.main.js",
+    "build:walk": "rollup -c rollup/config.walk.js",
+    "build:loose": "rollup -c rollup/config.loose.js && rollup -c rollup/config.loose_es.js",
+    "lint": "eslint src/"
+  },
+  "devDependencies": {
+    "eslint": "^4.10.0",
+    "eslint-config-standard": "^10.2.1",
+    "eslint-plugin-import": "^2.2.0",
+    "eslint-plugin-node": "^5.2.1",
+    "eslint-plugin-promise": "^3.5.0",
+    "eslint-plugin-standard": "^3.0.1",
+    "rollup": "^0.45.0",
+    "rollup-plugin-buble": "^0.16.0",
+    "test262": "git+https://github.com/tc39/test262.git#18c1e799a01cc976695983b61e225ce7959bdd91",
+    "test262-parser-runner": "^0.3.1",
+    "unicode-10.0.0": "^0.7.5"
+  }
+}
diff --git a/tools/tests/apps/modules/imports/links/acorn/src/.eslintrc b/tools/tests/apps/modules/imports/links/acorn/src/.eslintrc
new file mode 100644
index 0000000000..e636ee75db
--- /dev/null
+++ b/tools/tests/apps/modules/imports/links/acorn/src/.eslintrc
@@ -0,0 +1,33 @@
+{
+    "extends": [
+        "eslint:recommended",
+        "standard",
+        "plugin:import/errors",
+        "plugin:import/warnings"
+    ],
+    "rules": {
+        "curly": "off",
+        "eqeqeq": "off",
+        "indent": ["error", 2, { "SwitchCase": 0, "VariableDeclarator": 2, "CallExpression": { arguments: "off" } }],
+        "new-parens": "off",
+        "no-case-declarations": "off",
+        "no-cond-assign": "off",
+        "no-fallthrough": "off",
+        "no-labels": "off",
+        "no-mixed-operators": "off",
+        "no-return-assign": "off",
+        "no-unused-labels": "error",
+        "no-var": "error",
+        "object-curly-spacing": ["error", "never"],
+        "one-var": "off",
+        "quotes": ["error", "double"],
+        "semi-spacing": "off",
+        "space-before-function-paren": ["error", "never"]
+    },
+    "globals": {
+        "Packages": false
+    },
+    "plugins": [
+        "import"
+    ]
+}
diff --git a/tools/tests/apps/modules/imports/links/acorn/src/bin/.eslintrc b/tools/tests/apps/modules/imports/links/acorn/src/bin/.eslintrc
new file mode 100644
index 0000000000..2598b25f5f
--- /dev/null
+++ b/tools/tests/apps/modules/imports/links/acorn/src/bin/.eslintrc
@@ -0,0 +1,6 @@
+{
+    "extends": "../.eslintrc",
+    "rules": {
+        "no-console": "off"
+    }
+}
\ No newline at end of file
diff --git a/tools/tests/apps/modules/imports/links/acorn/src/bin/acorn.js b/tools/tests/apps/modules/imports/links/acorn/src/bin/acorn.js
new file mode 100644
index 0000000000..d5fe42521a
--- /dev/null
+++ b/tools/tests/apps/modules/imports/links/acorn/src/bin/acorn.js
@@ -0,0 +1,62 @@
+import {basename} from "path"
+import {readFileSync as readFile} from "fs"
+import * as acorn from "acorn"
+
+let infile, forceFile, silent = false, compact = false, tokenize = false
+const options = {}
+
+function help(status) {
+  const print = (status == 0) ? console.log : console.error
+  print("usage: " + basename(process.argv[1]) + " [--ecma3|--ecma5|--ecma6|--ecma7|--ecma8|--ecma9|...|--ecma2015|--ecma2016|--ecma2017|--ecma2018|...]")
+  print("        [--tokenize] [--locations] [---allow-hash-bang] [--compact] [--silent] [--module] [--help] [--] [infile]")
+  process.exit(status)
+}
+
+for (let i = 2; i < process.argv.length; ++i) {
+  const arg = process.argv[i]
+  if ((arg == "-" || arg[0] != "-") && !infile) infile = arg
+  else if (arg == "--" && !infile && i + 2 == process.argv.length) forceFile = infile = process.argv[++i]
+  else if (arg == "--locations") options.locations = true
+  else if (arg == "--allow-hash-bang") options.allowHashBang = true
+  else if (arg == "--silent") silent = true
+  else if (arg == "--compact") compact = true
+  else if (arg == "--help") help(0)
+  else if (arg == "--tokenize") tokenize = true
+  else if (arg == "--module") options.sourceType = "module"
+  else {
+    let match = arg.match(/^--ecma(\d+)$/)
+    if (match)
+      options.ecmaVersion = +match[1]
+    else
+      help(1)
+  }
+}
+
+function run(code) {
+  let result
+  try {
+    if (!tokenize) {
+      result = acorn.parse(code, options)
+    } else {
+      result = []
+      let tokenizer = acorn.tokenizer(code, options), token
+      do {
+        token = tokenizer.getToken()
+        result.push(token)
+      } while (token.type != acorn.tokTypes.eof)
+    }
+  } catch (e) {
+    console.error(e.message)
+    process.exit(1)
+  }
+  if (!silent) console.log(JSON.stringify(result, null, compact ? null : 2))
+}
+
+if (forceFile || infile && infile != "-") {
+  run(readFile(infile, "utf8"))
+} else {
+  let code = ""
+  process.stdin.resume()
+  process.stdin.on("data", chunk => code += chunk)
+  process.stdin.on("end", () => run(code))
+}
diff --git a/tools/tests/apps/modules/imports/links/acorn/src/expression.js b/tools/tests/apps/modules/imports/links/acorn/src/expression.js
new file mode 100644
index 0000000000..79cd9b559f
--- /dev/null
+++ b/tools/tests/apps/modules/imports/links/acorn/src/expression.js
@@ -0,0 +1,909 @@
+// A recursive descent parser operates by defining functions for all
+// syntactic elements, and recursively calling those, each function
+// advancing the input stream and returning an AST node. Precedence
+// of constructs (for example, the fact that `!x[1]` means `!(x[1])`
+// instead of `(!x)[1]` is handled by the fact that the parser
+// function that parses unary prefix operators is called first, and
+// in turn calls the function that parses `[]` subscripts — that
+// way, it'll receive the node for `x[1]` already parsed, and wraps
+// *that* in the unary operator node.
+//
+// Acorn uses an [operator precedence parser][opp] to handle binary
+// operator precedence, because it is much more compact than using
+// the technique outlined above, which uses different, nesting
+// functions to specify precedence, for all of the ten binary
+// precedence levels that JavaScript defines.
+//
+// [opp]: http://en.wikipedia.org/wiki/Operator-precedence_parser
+
+import {types as tt} from "./tokentype"
+import {Parser} from "./state"
+import {DestructuringErrors} from "./parseutil"
+import {lineBreak} from "./whitespace"
+
+const pp = Parser.prototype
+
+// Check if property name clashes with already added.
+// Object/class getters and setters are not allowed to clash —
+// either with each other or with an init property — and in
+// strict mode, init properties are also not allowed to be repeated.
+
+pp.checkPropClash = function(prop, propHash, refDestructuringErrors) {
+  if (this.options.ecmaVersion >= 9 && prop.type === "SpreadElement")
+    return
+  if (this.options.ecmaVersion >= 6 && (prop.computed || prop.method || prop.shorthand))
+    return
+  let {key} = prop, name
+  switch (key.type) {
+  case "Identifier": name = key.name; break
+  case "Literal": name = String(key.value); break
+  default: return
+  }
+  let {kind} = prop
+  if (this.options.ecmaVersion >= 6) {
+    if (name === "__proto__" && kind === "init") {
+      if (propHash.proto) {
+        if (refDestructuringErrors && refDestructuringErrors.doubleProto < 0) refDestructuringErrors.doubleProto = key.start
+        // Backwards-compat kludge. Can be removed in version 6.0
+        else this.raiseRecoverable(key.start, "Redefinition of __proto__ property")
+      }
+      propHash.proto = true
+    }
+    return
+  }
+  name = "$" + name
+  let other = propHash[name]
+  if (other) {
+    let redefinition
+    if (kind === "init") {
+      redefinition = this.strict && other.init || other.get || other.set
+    } else {
+      redefinition = other.init || other[kind]
+    }
+    if (redefinition)
+      this.raiseRecoverable(key.start, "Redefinition of property")
+  } else {
+    other = propHash[name] = {
+      init: false,
+      get: false,
+      set: false
+    }
+  }
+  other[kind] = true
+}
+
+// ### Expression parsing
+
+// These nest, from the most general expression type at the top to
+// 'atomic', nondivisible expression types at the bottom. Most of
+// the functions will simply let the function(s) below them parse,
+// and, *if* the syntactic construct they handle is present, wrap
+// the AST node that the inner parser gave them in another node.
+
+// Parse a full expression. The optional arguments are used to
+// forbid the `in` operator (in for loops initalization expressions)
+// and provide reference for storing '=' operator inside shorthand
+// property assignment in contexts where both object expression
+// and object pattern might appear (so it's possible to raise
+// delayed syntax error at correct position).
+
+pp.parseExpression = function(noIn, refDestructuringErrors) {
+  let startPos = this.start, startLoc = this.startLoc
+  let expr = this.parseMaybeAssign(noIn, refDestructuringErrors)
+  if (this.type === tt.comma) {
+    let node = this.startNodeAt(startPos, startLoc)
+    node.expressions = [expr]
+    while (this.eat(tt.comma)) node.expressions.push(this.parseMaybeAssign(noIn, refDestructuringErrors))
+    return this.finishNode(node, "SequenceExpression")
+  }
+  return expr
+}
+
+// Parse an assignment expression. This includes applications of
+// operators like `+=`.
+
+pp.parseMaybeAssign = function(noIn, refDestructuringErrors, afterLeftParse) {
+  if (this.inGenerator && this.isContextual("yield")) return this.parseYield()
+
+  let ownDestructuringErrors = false, oldParenAssign = -1, oldTrailingComma = -1
+  if (refDestructuringErrors) {
+    oldParenAssign = refDestructuringErrors.parenthesizedAssign
+    oldTrailingComma = refDestructuringErrors.trailingComma
+    refDestructuringErrors.parenthesizedAssign = refDestructuringErrors.trailingComma = -1
+  } else {
+    refDestructuringErrors = new DestructuringErrors
+    ownDestructuringErrors = true
+  }
+
+  let startPos = this.start, startLoc = this.startLoc
+  if (this.type == tt.parenL || this.type == tt.name)
+    this.potentialArrowAt = this.start
+  let left = this.parseMaybeConditional(noIn, refDestructuringErrors)
+  if (afterLeftParse) left = afterLeftParse.call(this, left, startPos, startLoc)
+  if (this.type.isAssign) {
+    let node = this.startNodeAt(startPos, startLoc)
+    node.operator = this.value
+    node.left = this.type === tt.eq ? this.toAssignable(left, false, refDestructuringErrors) : left
+    if (!ownDestructuringErrors) DestructuringErrors.call(refDestructuringErrors)
+    refDestructuringErrors.shorthandAssign = -1 // reset because shorthand default was used correctly
+    this.checkLVal(left)
+    this.next()
+    node.right = this.parseMaybeAssign(noIn)
+    return this.finishNode(node, "AssignmentExpression")
+  } else {
+    if (ownDestructuringErrors) this.checkExpressionErrors(refDestructuringErrors, true)
+  }
+  if (oldParenAssign > -1) refDestructuringErrors.parenthesizedAssign = oldParenAssign
+  if (oldTrailingComma > -1) refDestructuringErrors.trailingComma = oldTrailingComma
+  return left
+}
+
+// Parse a ternary conditional (`?:`) operator.
+
+pp.parseMaybeConditional = function(noIn, refDestructuringErrors) {
+  let startPos = this.start, startLoc = this.startLoc
+  let expr = this.parseExprOps(noIn, refDestructuringErrors)
+  if (this.checkExpressionErrors(refDestructuringErrors)) return expr
+  if (this.eat(tt.question)) {
+    let node = this.startNodeAt(startPos, startLoc)
+    node.test = expr
+    node.consequent = this.parseMaybeAssign()
+    this.expect(tt.colon)
+    node.alternate = this.parseMaybeAssign(noIn)
+    return this.finishNode(node, "ConditionalExpression")
+  }
+  return expr
+}
+
+// Start the precedence parser.
+
+pp.parseExprOps = function(noIn, refDestructuringErrors) {
+  let startPos = this.start, startLoc = this.startLoc
+  let expr = this.parseMaybeUnary(refDestructuringErrors, false)
+  if (this.checkExpressionErrors(refDestructuringErrors)) return expr
+  return expr.start == startPos && expr.type === "ArrowFunctionExpression" ? expr : this.parseExprOp(expr, startPos, startLoc, -1, noIn)
+}
+
+// Parse binary operators with the operator precedence parsing
+// algorithm. `left` is the left-hand side of the operator.
+// `minPrec` provides context that allows the function to stop and
+// defer further parser to one of its callers when it encounters an
+// operator that has a lower precedence than the set it is parsing.
+
+pp.parseExprOp = function(left, leftStartPos, leftStartLoc, minPrec, noIn) {
+  let prec = this.type.binop
+  if (prec != null && (!noIn || this.type !== tt._in)) {
+    if (prec > minPrec) {
+      let logical = this.type === tt.logicalOR || this.type === tt.logicalAND
+      let op = this.value
+      this.next()
+      let startPos = this.start, startLoc = this.startLoc
+      let right = this.parseExprOp(this.parseMaybeUnary(null, false), startPos, startLoc, prec, noIn)
+      let node = this.buildBinary(leftStartPos, leftStartLoc, left, right, op, logical)
+      return this.parseExprOp(node, leftStartPos, leftStartLoc, minPrec, noIn)
+    }
+  }
+  return left
+}
+
+pp.buildBinary = function(startPos, startLoc, left, right, op, logical) {
+  let node = this.startNodeAt(startPos, startLoc)
+  node.left = left
+  node.operator = op
+  node.right = right
+  return this.finishNode(node, logical ? "LogicalExpression" : "BinaryExpression")
+}
+
+// Parse unary operators, both prefix and postfix.
+
+pp.parseMaybeUnary = function(refDestructuringErrors, sawUnary) {
+  let startPos = this.start, startLoc = this.startLoc, expr
+  if (this.inAsync && this.isContextual("await")) {
+    expr = this.parseAwait()
+    sawUnary = true
+  } else if (this.type.prefix) {
+    let node = this.startNode(), update = this.type === tt.incDec
+    node.operator = this.value
+    node.prefix = true
+    this.next()
+    node.argument = this.parseMaybeUnary(null, true)
+    this.checkExpressionErrors(refDestructuringErrors, true)
+    if (update) this.checkLVal(node.argument)
+    else if (this.strict && node.operator === "delete" &&
+             node.argument.type === "Identifier")
+      this.raiseRecoverable(node.start, "Deleting local variable in strict mode")
+    else sawUnary = true
+    expr = this.finishNode(node, update ? "UpdateExpression" : "UnaryExpression")
+  } else {
+    expr = this.parseExprSubscripts(refDestructuringErrors)
+    if (this.checkExpressionErrors(refDestructuringErrors)) return expr
+    while (this.type.postfix && !this.canInsertSemicolon()) {
+      let node = this.startNodeAt(startPos, startLoc)
+      node.operator = this.value
+      node.prefix = false
+      node.argument = expr
+      this.checkLVal(expr)
+      this.next()
+      expr = this.finishNode(node, "UpdateExpression")
+    }
+  }
+
+  if (!sawUnary && this.eat(tt.starstar))
+    return this.buildBinary(startPos, startLoc, expr, this.parseMaybeUnary(null, false), "**", false)
+  else
+    return expr
+}
+
+// Parse call, dot, and `[]`-subscript expressions.
+
+pp.parseExprSubscripts = function(refDestructuringErrors) {
+  let startPos = this.start, startLoc = this.startLoc
+  let expr = this.parseExprAtom(refDestructuringErrors)
+  let skipArrowSubscripts = expr.type === "ArrowFunctionExpression" && this.input.slice(this.lastTokStart, this.lastTokEnd) !== ")"
+  if (this.checkExpressionErrors(refDestructuringErrors) || skipArrowSubscripts) return expr
+  let result = this.parseSubscripts(expr, startPos, startLoc)
+  if (refDestructuringErrors && result.type === "MemberExpression") {
+    if (refDestructuringErrors.parenthesizedAssign >= result.start) refDestructuringErrors.parenthesizedAssign = -1
+    if (refDestructuringErrors.parenthesizedBind >= result.start) refDestructuringErrors.parenthesizedBind = -1
+  }
+  return result
+}
+
+pp.parseSubscripts = function(base, startPos, startLoc, noCalls) {
+  let maybeAsyncArrow = this.options.ecmaVersion >= 8 && base.type === "Identifier" && base.name === "async" &&
+      this.lastTokEnd == base.end && !this.canInsertSemicolon() && this.input.slice(base.start, base.end) === "async"
+  for (let computed;;) {
+    if ((computed = this.eat(tt.bracketL)) || this.eat(tt.dot)) {
+      let node = this.startNodeAt(startPos, startLoc)
+      node.object = base
+      node.property = computed ? this.parseExpression() : this.parseIdent(true)
+      node.computed = !!computed
+      if (computed) this.expect(tt.bracketR)
+      base = this.finishNode(node, "MemberExpression")
+    } else if (!noCalls && this.eat(tt.parenL)) {
+      let refDestructuringErrors = new DestructuringErrors, oldYieldPos = this.yieldPos, oldAwaitPos = this.awaitPos
+      this.yieldPos = 0
+      this.awaitPos = 0
+      let exprList = this.parseExprList(tt.parenR, this.options.ecmaVersion >= 8, false, refDestructuringErrors)
+      if (maybeAsyncArrow && !this.canInsertSemicolon() && this.eat(tt.arrow)) {
+        this.checkPatternErrors(refDestructuringErrors, false)
+        this.checkYieldAwaitInDefaultParams()
+        this.yieldPos = oldYieldPos
+        this.awaitPos = oldAwaitPos
+        return this.parseArrowExpression(this.startNodeAt(startPos, startLoc), exprList, true)
+      }
+      this.checkExpressionErrors(refDestructuringErrors, true)
+      this.yieldPos = oldYieldPos || this.yieldPos
+      this.awaitPos = oldAwaitPos || this.awaitPos
+      let node = this.startNodeAt(startPos, startLoc)
+      node.callee = base
+      node.arguments = exprList
+      base = this.finishNode(node, "CallExpression")
+    } else if (this.type === tt.backQuote) {
+      let node = this.startNodeAt(startPos, startLoc)
+      node.tag = base
+      node.quasi = this.parseTemplate({isTagged: true})
+      base = this.finishNode(node, "TaggedTemplateExpression")
+    } else {
+      return base
+    }
+  }
+}
+
+// Parse an atomic expression — either a single token that is an
+// expression, an expression started by a keyword like `function` or
+// `new`, or an expression wrapped in punctuation like `()`, `[]`,
+// or `{}`.
+
+pp.parseExprAtom = function(refDestructuringErrors) {
+  let node, canBeArrow = this.potentialArrowAt == this.start
+  switch (this.type) {
+  case tt._super:
+    if (!this.inFunction)
+      this.raise(this.start, "'super' outside of function or class")
+    node = this.startNode()
+    this.next()
+    // The `super` keyword can appear at below:
+    // SuperProperty:
+    //     super [ Expression ]
+    //     super . IdentifierName
+    // SuperCall:
+    //     super Arguments
+    if (this.type !== tt.dot && this.type !== tt.bracketL && this.type !== tt.parenL)
+      this.unexpected()
+    return this.finishNode(node, "Super")
+
+  case tt._this:
+    node = this.startNode()
+    this.next()
+    return this.finishNode(node, "ThisExpression")
+
+  case tt.name:
+    let startPos = this.start, startLoc = this.startLoc, containsEsc = this.containsEsc
+    let id = this.parseIdent(this.type !== tt.name)
+    if (this.options.ecmaVersion >= 8 && !containsEsc && id.name === "async" && !this.canInsertSemicolon() && this.eat(tt._function))
+      return this.parseFunction(this.startNodeAt(startPos, startLoc), false, false, true)
+    if (canBeArrow && !this.canInsertSemicolon()) {
+      if (this.eat(tt.arrow))
+        return this.parseArrowExpression(this.startNodeAt(startPos, startLoc), [id], false)
+      if (this.options.ecmaVersion >= 8 && id.name === "async" && this.type === tt.name && !containsEsc) {
+        id = this.parseIdent()
+        if (this.canInsertSemicolon() || !this.eat(tt.arrow))
+          this.unexpected()
+        return this.parseArrowExpression(this.startNodeAt(startPos, startLoc), [id], true)
+      }
+    }
+    return id
+
+  case tt.regexp:
+    let value = this.value
+    node = this.parseLiteral(value.value)
+    node.regex = {pattern: value.pattern, flags: value.flags}
+    return node
+
+  case tt.num: case tt.string:
+    return this.parseLiteral(this.value)
+
+  case tt._null: case tt._true: case tt._false:
+    node = this.startNode()
+    node.value = this.type === tt._null ? null : this.type === tt._true
+    node.raw = this.type.keyword
+    this.next()
+    return this.finishNode(node, "Literal")
+
+  case tt.parenL:
+    let start = this.start, expr = this.parseParenAndDistinguishExpression(canBeArrow)
+    if (refDestructuringErrors) {
+      if (refDestructuringErrors.parenthesizedAssign < 0 && !this.isSimpleAssignTarget(expr))
+        refDestructuringErrors.parenthesizedAssign = start
+      if (refDestructuringErrors.parenthesizedBind < 0)
+        refDestructuringErrors.parenthesizedBind = start
+    }
+    return expr
+
+  case tt.bracketL:
+    node = this.startNode()
+    this.next()
+    node.elements = this.parseExprList(tt.bracketR, true, true, refDestructuringErrors)
+    return this.finishNode(node, "ArrayExpression")
+
+  case tt.braceL:
+    return this.parseObj(false, refDestructuringErrors)
+
+  case tt._function:
+    node = this.startNode()
+    this.next()
+    return this.parseFunction(node, false)
+
+  case tt._class:
+    return this.parseClass(this.startNode(), false)
+
+  case tt._new:
+    return this.parseNew()
+
+  case tt.backQuote:
+    return this.parseTemplate()
+
+  default:
+    this.unexpected()
+  }
+}
+
+pp.parseLiteral = function(value) {
+  let node = this.startNode()
+  node.value = value
+  node.raw = this.input.slice(this.start, this.end)
+  this.next()
+  return this.finishNode(node, "Literal")
+}
+
+pp.parseParenExpression = function() {
+  this.expect(tt.parenL)
+  let val = this.parseExpression()
+  this.expect(tt.parenR)
+  return val
+}
+
+pp.parseParenAndDistinguishExpression = function(canBeArrow) {
+  let startPos = this.start, startLoc = this.startLoc, val, allowTrailingComma = this.options.ecmaVersion >= 8
+  if (this.options.ecmaVersion >= 6) {
+    this.next()
+
+    let innerStartPos = this.start, innerStartLoc = this.startLoc
+    let exprList = [], first = true, lastIsComma = false
+    let refDestructuringErrors = new DestructuringErrors, oldYieldPos = this.yieldPos, oldAwaitPos = this.awaitPos, spreadStart
+    this.yieldPos = 0
+    this.awaitPos = 0
+    while (this.type !== tt.parenR) {
+      first ? first = false : this.expect(tt.comma)
+      if (allowTrailingComma && this.afterTrailingComma(tt.parenR, true)) {
+        lastIsComma = true
+        break
+      } else if (this.type === tt.ellipsis) {
+        spreadStart = this.start
+        exprList.push(this.parseParenItem(this.parseRestBinding()))
+        if (this.type === tt.comma) this.raise(this.start, "Comma is not permitted after the rest element")
+        break
+      } else {
+        exprList.push(this.parseMaybeAssign(false, refDestructuringErrors, this.parseParenItem))
+      }
+    }
+    let innerEndPos = this.start, innerEndLoc = this.startLoc
+    this.expect(tt.parenR)
+
+    if (canBeArrow && !this.canInsertSemicolon() && this.eat(tt.arrow)) {
+      this.checkPatternErrors(refDestructuringErrors, false)
+      this.checkYieldAwaitInDefaultParams()
+      this.yieldPos = oldYieldPos
+      this.awaitPos = oldAwaitPos
+      return this.parseParenArrowList(startPos, startLoc, exprList)
+    }
+
+    if (!exprList.length || lastIsComma) this.unexpected(this.lastTokStart)
+    if (spreadStart) this.unexpected(spreadStart)
+    this.checkExpressionErrors(refDestructuringErrors, true)
+    this.yieldPos = oldYieldPos || this.yieldPos
+    this.awaitPos = oldAwaitPos || this.awaitPos
+
+    if (exprList.length > 1) {
+      val = this.startNodeAt(innerStartPos, innerStartLoc)
+      val.expressions = exprList
+      this.finishNodeAt(val, "SequenceExpression", innerEndPos, innerEndLoc)
+    } else {
+      val = exprList[0]
+    }
+  } else {
+    val = this.parseParenExpression()
+  }
+
+  if (this.options.preserveParens) {
+    let par = this.startNodeAt(startPos, startLoc)
+    par.expression = val
+    return this.finishNode(par, "ParenthesizedExpression")
+  } else {
+    return val
+  }
+}
+
+pp.parseParenItem = function(item) {
+  return item
+}
+
+pp.parseParenArrowList = function(startPos, startLoc, exprList) {
+  return this.parseArrowExpression(this.startNodeAt(startPos, startLoc), exprList)
+}
+
+// New's precedence is slightly tricky. It must allow its argument to
+// be a `[]` or dot subscript expression, but not a call — at least,
+// not without wrapping it in parentheses. Thus, it uses the noCalls
+// argument to parseSubscripts to prevent it from consuming the
+// argument list.
+
+const empty = []
+
+pp.parseNew = function() {
+  let node = this.startNode()
+  let meta = this.parseIdent(true)
+  if (this.options.ecmaVersion >= 6 && this.eat(tt.dot)) {
+    node.meta = meta
+    let containsEsc = this.containsEsc
+    node.property = this.parseIdent(true)
+    if (node.property.name !== "target" || containsEsc)
+      this.raiseRecoverable(node.property.start, "The only valid meta property for new is new.target")
+    if (!this.inFunction)
+      this.raiseRecoverable(node.start, "new.target can only be used in functions")
+    return this.finishNode(node, "MetaProperty")
+  }
+  let startPos = this.start, startLoc = this.startLoc
+  node.callee = this.parseSubscripts(this.parseExprAtom(), startPos, startLoc, true)
+  if (this.eat(tt.parenL)) node.arguments = this.parseExprList(tt.parenR, this.options.ecmaVersion >= 8, false)
+  else node.arguments = empty
+  return this.finishNode(node, "NewExpression")
+}
+
+// Parse template expression.
+
+pp.parseTemplateElement = function({isTagged}) {
+  let elem = this.startNode()
+  if (this.type === tt.invalidTemplate) {
+    if (!isTagged) {
+      this.raiseRecoverable(this.start, "Bad escape sequence in untagged template literal")
+    }
+    elem.value = {
+      raw: this.value,
+      cooked: null
+    }
+  } else {
+    elem.value = {
+      raw: this.input.slice(this.start, this.end).replace(/\r\n?/g, "\n"),
+      cooked: this.value
+    }
+  }
+  this.next()
+  elem.tail = this.type === tt.backQuote
+  return this.finishNode(elem, "TemplateElement")
+}
+
+pp.parseTemplate = function({isTagged = false} = {}) {
+  let node = this.startNode()
+  this.next()
+  node.expressions = []
+  let curElt = this.parseTemplateElement({isTagged})
+  node.quasis = [curElt]
+  while (!curElt.tail) {
+    this.expect(tt.dollarBraceL)
+    node.expressions.push(this.parseExpression())
+    this.expect(tt.braceR)
+    node.quasis.push(curElt = this.parseTemplateElement({isTagged}))
+  }
+  this.next()
+  return this.finishNode(node, "TemplateLiteral")
+}
+
+pp.isAsyncProp = function(prop) {
+  return !prop.computed && prop.key.type === "Identifier" && prop.key.name === "async" &&
+    (this.type === tt.name || this.type === tt.num || this.type === tt.string || this.type === tt.bracketL || this.type.keyword || (this.options.ecmaVersion >= 9 && this.type === tt.star)) &&
+    !lineBreak.test(this.input.slice(this.lastTokEnd, this.start))
+}
+
+// Parse an object literal or binding pattern.
+
+pp.parseObj = function(isPattern, refDestructuringErrors) {
+  let node = this.startNode(), first = true, propHash = {}
+  node.properties = []
+  this.next()
+  while (!this.eat(tt.braceR)) {
+    if (!first) {
+      this.expect(tt.comma)
+      if (this.afterTrailingComma(tt.braceR)) break
+    } else first = false
+
+    const prop = this.parseProperty(isPattern, refDestructuringErrors)
+    if (!isPattern) this.checkPropClash(prop, propHash, refDestructuringErrors)
+    node.properties.push(prop)
+  }
+  return this.finishNode(node, isPattern ? "ObjectPattern" : "ObjectExpression")
+}
+
+pp.parseProperty = function(isPattern, refDestructuringErrors) {
+  let prop = this.startNode(), isGenerator, isAsync, startPos, startLoc
+  if (this.options.ecmaVersion >= 9 && this.eat(tt.ellipsis)) {
+    if (isPattern) {
+      prop.argument = this.parseIdent(false)
+      if (this.type === tt.comma) {
+        this.raise(this.start, "Comma is not permitted after the rest element")
+      }
+      return this.finishNode(prop, "RestElement")
+    }
+    // To disallow parenthesized identifier via `this.toAssignable()`.
+    if (this.type === tt.parenL && refDestructuringErrors) {
+      if (refDestructuringErrors.parenthesizedAssign < 0) {
+        refDestructuringErrors.parenthesizedAssign = this.start
+      }
+      if (refDestructuringErrors.parenthesizedBind < 0) {
+        refDestructuringErrors.parenthesizedBind = this.start
+      }
+    }
+    // Parse argument.
+    prop.argument = this.parseMaybeAssign(false, refDestructuringErrors)
+    // To disallow trailing comma via `this.toAssignable()`.
+    if (this.type === tt.comma && refDestructuringErrors && refDestructuringErrors.trailingComma < 0) {
+      refDestructuringErrors.trailingComma = this.start
+    }
+    // Finish
+    return this.finishNode(prop, "SpreadElement")
+  }
+  if (this.options.ecmaVersion >= 6) {
+    prop.method = false
+    prop.shorthand = false
+    if (isPattern || refDestructuringErrors) {
+      startPos = this.start
+      startLoc = this.startLoc
+    }
+    if (!isPattern)
+      isGenerator = this.eat(tt.star)
+  }
+  let containsEsc = this.containsEsc
+  this.parsePropertyName(prop)
+  if (!isPattern && !containsEsc && this.options.ecmaVersion >= 8 && !isGenerator && this.isAsyncProp(prop)) {
+    isAsync = true
+    isGenerator = this.options.ecmaVersion >= 9 && this.eat(tt.star)
+    this.parsePropertyName(prop, refDestructuringErrors)
+  } else {
+    isAsync = false
+  }
+  this.parsePropertyValue(prop, isPattern, isGenerator, isAsync, startPos, startLoc, refDestructuringErrors, containsEsc)
+  return this.finishNode(prop, "Property")
+}
+
+pp.parsePropertyValue = function(prop, isPattern, isGenerator, isAsync, startPos, startLoc, refDestructuringErrors, containsEsc) {
+  if ((isGenerator || isAsync) && this.type === tt.colon)
+    this.unexpected()
+
+  if (this.eat(tt.colon)) {
+    prop.value = isPattern ? this.parseMaybeDefault(this.start, this.startLoc) : this.parseMaybeAssign(false, refDestructuringErrors)
+    prop.kind = "init"
+  } else if (this.options.ecmaVersion >= 6 && this.type === tt.parenL) {
+    if (isPattern) this.unexpected()
+    prop.kind = "init"
+    prop.method = true
+    prop.value = this.parseMethod(isGenerator, isAsync)
+  } else if (!isPattern && !containsEsc &&
+             this.options.ecmaVersion >= 5 && !prop.computed && prop.key.type === "Identifier" &&
+             (prop.key.name === "get" || prop.key.name === "set") &&
+             (this.type != tt.comma && this.type != tt.braceR)) {
+    if (isGenerator || isAsync) this.unexpected()
+    prop.kind = prop.key.name
+    this.parsePropertyName(prop)
+    prop.value = this.parseMethod(false)
+    let paramCount = prop.kind === "get" ? 0 : 1
+    if (prop.value.params.length !== paramCount) {
+      let start = prop.value.start
+      if (prop.kind === "get")
+        this.raiseRecoverable(start, "getter should have no params")
+      else
+        this.raiseRecoverable(start, "setter should have exactly one param")
+    } else {
+      if (prop.kind === "set" && prop.value.params[0].type === "RestElement")
+        this.raiseRecoverable(prop.value.params[0].start, "Setter cannot use rest params")
+    }
+  } else if (this.options.ecmaVersion >= 6 && !prop.computed && prop.key.type === "Identifier") {
+    this.checkUnreserved(prop.key)
+    prop.kind = "init"
+    if (isPattern) {
+      prop.value = this.parseMaybeDefault(startPos, startLoc, prop.key)
+    } else if (this.type === tt.eq && refDestructuringErrors) {
+      if (refDestructuringErrors.shorthandAssign < 0)
+        refDestructuringErrors.shorthandAssign = this.start
+      prop.value = this.parseMaybeDefault(startPos, startLoc, prop.key)
+    } else {
+      prop.value = prop.key
+    }
+    prop.shorthand = true
+  } else this.unexpected()
+}
+
+pp.parsePropertyName = function(prop) {
+  if (this.options.ecmaVersion >= 6) {
+    if (this.eat(tt.bracketL)) {
+      prop.computed = true
+      prop.key = this.parseMaybeAssign()
+      this.expect(tt.bracketR)
+      return prop.key
+    } else {
+      prop.computed = false
+    }
+  }
+  return prop.key = this.type === tt.num || this.type === tt.string ? this.parseExprAtom() : this.parseIdent(true)
+}
+
+// Initialize empty function node.
+
+pp.initFunction = function(node) {
+  node.id = null
+  if (this.options.ecmaVersion >= 6) {
+    node.generator = false
+    node.expression = false
+  }
+  if (this.options.ecmaVersion >= 8)
+    node.async = false
+}
+
+// Parse object or class method.
+
+pp.parseMethod = function(isGenerator, isAsync) {
+  let node = this.startNode(), oldInGen = this.inGenerator, oldInAsync = this.inAsync,
+      oldYieldPos = this.yieldPos, oldAwaitPos = this.awaitPos, oldInFunc = this.inFunction
+
+  this.initFunction(node)
+  if (this.options.ecmaVersion >= 6)
+    node.generator = isGenerator
+  if (this.options.ecmaVersion >= 8)
+    node.async = !!isAsync
+
+  this.inGenerator = node.generator
+  this.inAsync = node.async
+  this.yieldPos = 0
+  this.awaitPos = 0
+  this.inFunction = true
+  this.enterFunctionScope()
+
+  this.expect(tt.parenL)
+  node.params = this.parseBindingList(tt.parenR, false, this.options.ecmaVersion >= 8)
+  this.checkYieldAwaitInDefaultParams()
+  this.parseFunctionBody(node, false)
+
+  this.inGenerator = oldInGen
+  this.inAsync = oldInAsync
+  this.yieldPos = oldYieldPos
+  this.awaitPos = oldAwaitPos
+  this.inFunction = oldInFunc
+  return this.finishNode(node, "FunctionExpression")
+}
+
+// Parse arrow function expression with given parameters.
+
+pp.parseArrowExpression = function(node, params, isAsync) {
+  let oldInGen = this.inGenerator, oldInAsync = this.inAsync,
+      oldYieldPos = this.yieldPos, oldAwaitPos = this.awaitPos, oldInFunc = this.inFunction
+
+  this.enterFunctionScope()
+  this.initFunction(node)
+  if (this.options.ecmaVersion >= 8)
+    node.async = !!isAsync
+
+  this.inGenerator = false
+  this.inAsync = node.async
+  this.yieldPos = 0
+  this.awaitPos = 0
+  this.inFunction = true
+
+  node.params = this.toAssignableList(params, true)
+  this.parseFunctionBody(node, true)
+
+  this.inGenerator = oldInGen
+  this.inAsync = oldInAsync
+  this.yieldPos = oldYieldPos
+  this.awaitPos = oldAwaitPos
+  this.inFunction = oldInFunc
+  return this.finishNode(node, "ArrowFunctionExpression")
+}
+
+// Parse function body and check parameters.
+
+pp.parseFunctionBody = function(node, isArrowFunction) {
+  let isExpression = isArrowFunction && this.type !== tt.braceL
+  let oldStrict = this.strict, useStrict = false
+
+  if (isExpression) {
+    node.body = this.parseMaybeAssign()
+    node.expression = true
+    this.checkParams(node, false)
+  } else {
+    let nonSimple = this.options.ecmaVersion >= 7 && !this.isSimpleParamList(node.params)
+    if (!oldStrict || nonSimple) {
+      useStrict = this.strictDirective(this.end)
+      // If this is a strict mode function, verify that argument names
+      // are not repeated, and it does not try to bind the words `eval`
+      // or `arguments`.
+      if (useStrict && nonSimple)
+        this.raiseRecoverable(node.start, "Illegal 'use strict' directive in function with non-simple parameter list")
+    }
+    // Start a new scope with regard to labels and the `inFunction`
+    // flag (restore them to their old value afterwards).
+    let oldLabels = this.labels
+    this.labels = []
+    if (useStrict) this.strict = true
+
+    // Add the params to varDeclaredNames to ensure that an error is thrown
+    // if a let/const declaration in the function clashes with one of the params.
+    this.checkParams(node, !oldStrict && !useStrict && !isArrowFunction && this.isSimpleParamList(node.params))
+    node.body = this.parseBlock(false)
+    node.expression = false
+    this.adaptDirectivePrologue(node.body.body)
+    this.labels = oldLabels
+  }
+  this.exitFunctionScope()
+
+  if (this.strict && node.id) {
+    // Ensure the function name isn't a forbidden identifier in strict mode, e.g. 'eval'
+    this.checkLVal(node.id, "none")
+  }
+  this.strict = oldStrict
+}
+
+pp.isSimpleParamList = function(params) {
+  for (let param of params)
+    if (param.type !== "Identifier") return false
+  return true
+}
+
+// Checks function params for various disallowed patterns such as using "eval"
+// or "arguments" and duplicate parameters.
+
+pp.checkParams = function(node, allowDuplicates) {
+  let nameHash = {}
+  for (let param of node.params)
+    this.checkLVal(param, "var", allowDuplicates ? null : nameHash)
+}
+
+// Parses a comma-separated list of expressions, and returns them as
+// an array. `close` is the token type that ends the list, and
+// `allowEmpty` can be turned on to allow subsequent commas with
+// nothing in between them to be parsed as `null` (which is needed
+// for array literals).
+
+pp.parseExprList = function(close, allowTrailingComma, allowEmpty, refDestructuringErrors) {
+  let elts = [], first = true
+  while (!this.eat(close)) {
+    if (!first) {
+      this.expect(tt.comma)
+      if (allowTrailingComma && this.afterTrailingComma(close)) break
+    } else first = false
+
+    let elt
+    if (allowEmpty && this.type === tt.comma)
+      elt = null
+    else if (this.type === tt.ellipsis) {
+      elt = this.parseSpread(refDestructuringErrors)
+      if (refDestructuringErrors && this.type === tt.comma && refDestructuringErrors.trailingComma < 0)
+        refDestructuringErrors.trailingComma = this.start
+    } else {
+      elt = this.parseMaybeAssign(false, refDestructuringErrors)
+    }
+    elts.push(elt)
+  }
+  return elts
+}
+
+pp.checkUnreserved = function({start, end, name}) {
+  if (this.inGenerator && name === "yield")
+    this.raiseRecoverable(start, "Can not use 'yield' as identifier inside a generator")
+  if (this.inAsync && name === "await")
+    this.raiseRecoverable(start, "Can not use 'await' as identifier inside an async function")
+  if (this.isKeyword(name))
+    this.raise(start, `Unexpected keyword '${name}'`)
+  if (this.options.ecmaVersion < 6 &&
+    this.input.slice(start, end).indexOf("\\") != -1) return
+  const re = this.strict ? this.reservedWordsStrict : this.reservedWords
+  if (re.test(name)) {
+    if (!this.inAsync && name === "await")
+      this.raiseRecoverable(start, "Can not use keyword 'await' outside an async function")
+    this.raiseRecoverable(start, `The keyword '${name}' is reserved`)
+  }
+}
+
+// Parse the next token as an identifier. If `liberal` is true (used
+// when parsing properties), it will also convert keywords into
+// identifiers.
+
+pp.parseIdent = function(liberal, isBinding) {
+  let node = this.startNode()
+  if (liberal && this.options.allowReserved == "never") liberal = false
+  if (this.type === tt.name) {
+    node.name = this.value
+  } else if (this.type.keyword) {
+    node.name = this.type.keyword
+
+    // To fix https://github.com/acornjs/acorn/issues/575
+    // `class` and `function` keywords push new context into this.context.
+    // But there is no chance to pop the context if the keyword is consumed as an identifier such as a property name.
+    // If the previous token is a dot, this does not apply because the context-managing code already ignored the keyword
+    if ((node.name === "class" || node.name === "function") &&
+        (this.lastTokEnd !== this.lastTokStart + 1 || this.input.charCodeAt(this.lastTokStart) !== 46)) {
+      this.context.pop()
+    }
+  } else {
+    this.unexpected()
+  }
+  this.next()
+  this.finishNode(node, "Identifier")
+  if (!liberal) this.checkUnreserved(node)
+  return node
+}
+
+// Parses yield expression inside generator.
+
+pp.parseYield = function() {
+  if (!this.yieldPos) this.yieldPos = this.start
+
+  let node = this.startNode()
+  this.next()
+  if (this.type == tt.semi || this.canInsertSemicolon() || (this.type != tt.star && !this.type.startsExpr)) {
+    node.delegate = false
+    node.argument = null
+  } else {
+    node.delegate = this.eat(tt.star)
+    node.argument = this.parseMaybeAssign()
+  }
+  return this.finishNode(node, "YieldExpression")
+}
+
+pp.parseAwait = function() {
+  if (!this.awaitPos) this.awaitPos = this.start
+
+  let node = this.startNode()
+  this.next()
+  node.argument = this.parseMaybeUnary(null, true)
+  return this.finishNode(node, "AwaitExpression")
+}
diff --git a/tools/tests/apps/modules/imports/links/acorn/src/identifier.js b/tools/tests/apps/modules/imports/links/acorn/src/identifier.js
new file mode 100644
index 0000000000..5b6553b604
--- /dev/null
+++ b/tools/tests/apps/modules/imports/links/acorn/src/identifier.js
@@ -0,0 +1,87 @@
+// Reserved word lists for various dialects of the language
+
+export const reservedWords = {
+  3: "abstract boolean byte char class double enum export extends final float goto implements import int interface long native package private protected public short static super synchronized throws transient volatile",
+  5: "class enum extends super const export import",
+  6: "enum",
+  strict: "implements interface let package private protected public static yield",
+  strictBind: "eval arguments"
+}
+
+// And the keywords
+
+const ecma5AndLessKeywords = "break case catch continue debugger default do else finally for function if return switch throw try var while with null true false instanceof typeof void delete new in this"
+
+export const keywords = {
+  5: ecma5AndLessKeywords,
+  6: ecma5AndLessKeywords + " const class extends export import super"
+}
+
+export const keywordRelationalOperator = /^in(stanceof)?$/
+
+// ## Character categories
+
+// Big ugly regular expressions that match characters in the
+// whitespace, identifier, and identifier-start categories. These
+// are only applied when a character is found to actually have a
+// code point above 128.
+// Generated by `bin/generate-identifier-regex.js`.
+
+let nonASCIIidentifierStartChars = "\xaa\xb5\xba\xc0-\xd6\xd8-\xf6\xf8-\u02c1\u02c6-\u02d1\u02e0-\u02e4\u02ec\u02ee\u0370-\u0374\u0376\u0377\u037a-\u037d\u037f\u0386\u0388-\u038a\u038c\u038e-\u03a1\u03a3-\u03f5\u03f7-\u0481\u048a-\u052f\u0531-\u0556\u0559\u0561-\u0587\u05d0-\u05ea\u05f0-\u05f2\u0620-\u064a\u066e\u066f\u0671-\u06d3\u06d5\u06e5\u06e6\u06ee\u06ef\u06fa-\u06fc\u06ff\u0710\u0712-\u072f\u074d-\u07a5\u07b1\u07ca-\u07ea\u07f4\u07f5\u07fa\u0800-\u0815\u081a\u0824\u0828\u0840-\u0858\u0860-\u086a\u08a0-\u08b4\u08b6-\u08bd\u0904-\u0939\u093d\u0950\u0958-\u0961\u0971-\u0980\u0985-\u098c\u098f\u0990\u0993-\u09a8\u09aa-\u09b0\u09b2\u09b6-\u09b9\u09bd\u09ce\u09dc\u09dd\u09df-\u09e1\u09f0\u09f1\u09fc\u0a05-\u0a0a\u0a0f\u0a10\u0a13-\u0a28\u0a2a-\u0a30\u0a32\u0a33\u0a35\u0a36\u0a38\u0a39\u0a59-\u0a5c\u0a5e\u0a72-\u0a74\u0a85-\u0a8d\u0a8f-\u0a91\u0a93-\u0aa8\u0aaa-\u0ab0\u0ab2\u0ab3\u0ab5-\u0ab9\u0abd\u0ad0\u0ae0\u0ae1\u0af9\u0b05-\u0b0c\u0b0f\u0b10\u0b13-\u0b28\u0b2a-\u0b30\u0b32\u0b33\u0b35-\u0b39\u0b3d\u0b5c\u0b5d\u0b5f-\u0b61\u0b71\u0b83\u0b85-\u0b8a\u0b8e-\u0b90\u0b92-\u0b95\u0b99\u0b9a\u0b9c\u0b9e\u0b9f\u0ba3\u0ba4\u0ba8-\u0baa\u0bae-\u0bb9\u0bd0\u0c05-\u0c0c\u0c0e-\u0c10\u0c12-\u0c28\u0c2a-\u0c39\u0c3d\u0c58-\u0c5a\u0c60\u0c61\u0c80\u0c85-\u0c8c\u0c8e-\u0c90\u0c92-\u0ca8\u0caa-\u0cb3\u0cb5-\u0cb9\u0cbd\u0cde\u0ce0\u0ce1\u0cf1\u0cf2\u0d05-\u0d0c\u0d0e-\u0d10\u0d12-\u0d3a\u0d3d\u0d4e\u0d54-\u0d56\u0d5f-\u0d61\u0d7a-\u0d7f\u0d85-\u0d96\u0d9a-\u0db1\u0db3-\u0dbb\u0dbd\u0dc0-\u0dc6\u0e01-\u0e30\u0e32\u0e33\u0e40-\u0e46\u0e81\u0e82\u0e84\u0e87\u0e88\u0e8a\u0e8d\u0e94-\u0e97\u0e99-\u0e9f\u0ea1-\u0ea3\u0ea5\u0ea7\u0eaa\u0eab\u0ead-\u0eb0\u0eb2\u0eb3\u0ebd\u0ec0-\u0ec4\u0ec6\u0edc-\u0edf\u0f00\u0f40-\u0f47\u0f49-\u0f6c\u0f88-\u0f8c\u1000-\u102a\u103f\u1050-\u1055\u105a-\u105d\u1061\u1065\u1066\u106e-\u1070\u1075-\u1081\u108e\u10a0-\u10c5\u10c7\u10cd\u10d0-\u10fa\u10fc-\u1248\u124a-\u124d\u1250-\u1256\u1258\u125a-\u125d\u1260-\u1288\u128a-\u128d\u1290-\u12b0\u12b2-\u12b5\u12b8-\u12be\u12c0\u12c2-\u12c5\u12c8-\u12d6\u12d8-\u1310\u1312-\u1315\u1318-\u135a\u1380-\u138f\u13a0-\u13f5\u13f8-\u13fd\u1401-\u166c\u166f-\u167f\u1681-\u169a\u16a0-\u16ea\u16ee-\u16f8\u1700-\u170c\u170e-\u1711\u1720-\u1731\u1740-\u1751\u1760-\u176c\u176e-\u1770\u1780-\u17b3\u17d7\u17dc\u1820-\u1877\u1880-\u18a8\u18aa\u18b0-\u18f5\u1900-\u191e\u1950-\u196d\u1970-\u1974\u1980-\u19ab\u19b0-\u19c9\u1a00-\u1a16\u1a20-\u1a54\u1aa7\u1b05-\u1b33\u1b45-\u1b4b\u1b83-\u1ba0\u1bae\u1baf\u1bba-\u1be5\u1c00-\u1c23\u1c4d-\u1c4f\u1c5a-\u1c7d\u1c80-\u1c88\u1ce9-\u1cec\u1cee-\u1cf1\u1cf5\u1cf6\u1d00-\u1dbf\u1e00-\u1f15\u1f18-\u1f1d\u1f20-\u1f45\u1f48-\u1f4d\u1f50-\u1f57\u1f59\u1f5b\u1f5d\u1f5f-\u1f7d\u1f80-\u1fb4\u1fb6-\u1fbc\u1fbe\u1fc2-\u1fc4\u1fc6-\u1fcc\u1fd0-\u1fd3\u1fd6-\u1fdb\u1fe0-\u1fec\u1ff2-\u1ff4\u1ff6-\u1ffc\u2071\u207f\u2090-\u209c\u2102\u2107\u210a-\u2113\u2115\u2118-\u211d\u2124\u2126\u2128\u212a-\u2139\u213c-\u213f\u2145-\u2149\u214e\u2160-\u2188\u2c00-\u2c2e\u2c30-\u2c5e\u2c60-\u2ce4\u2ceb-\u2cee\u2cf2\u2cf3\u2d00-\u2d25\u2d27\u2d2d\u2d30-\u2d67\u2d6f\u2d80-\u2d96\u2da0-\u2da6\u2da8-\u2dae\u2db0-\u2db6\u2db8-\u2dbe\u2dc0-\u2dc6\u2dc8-\u2dce\u2dd0-\u2dd6\u2dd8-\u2dde\u3005-\u3007\u3021-\u3029\u3031-\u3035\u3038-\u303c\u3041-\u3096\u309b-\u309f\u30a1-\u30fa\u30fc-\u30ff\u3105-\u312e\u3131-\u318e\u31a0-\u31ba\u31f0-\u31ff\u3400-\u4db5\u4e00-\u9fea\ua000-\ua48c\ua4d0-\ua4fd\ua500-\ua60c\ua610-\ua61f\ua62a\ua62b\ua640-\ua66e\ua67f-\ua69d\ua6a0-\ua6ef\ua717-\ua71f\ua722-\ua788\ua78b-\ua7ae\ua7b0-\ua7b7\ua7f7-\ua801\ua803-\ua805\ua807-\ua80a\ua80c-\ua822\ua840-\ua873\ua882-\ua8b3\ua8f2-\ua8f7\ua8fb\ua8fd\ua90a-\ua925\ua930-\ua946\ua960-\ua97c\ua984-\ua9b2\ua9cf\ua9e0-\ua9e4\ua9e6-\ua9ef\ua9fa-\ua9fe\uaa00-\uaa28\uaa40-\uaa42\uaa44-\uaa4b\uaa60-\uaa76\uaa7a\uaa7e-\uaaaf\uaab1\uaab5\uaab6\uaab9-\uaabd\uaac0\uaac2\uaadb-\uaadd\uaae0-\uaaea\uaaf2-\uaaf4\uab01-\uab06\uab09-\uab0e\uab11-\uab16\uab20-\uab26\uab28-\uab2e\uab30-\uab5a\uab5c-\uab65\uab70-\uabe2\uac00-\ud7a3\ud7b0-\ud7c6\ud7cb-\ud7fb\uf900-\ufa6d\ufa70-\ufad9\ufb00-\ufb06\ufb13-\ufb17\ufb1d\ufb1f-\ufb28\ufb2a-\ufb36\ufb38-\ufb3c\ufb3e\ufb40\ufb41\ufb43\ufb44\ufb46-\ufbb1\ufbd3-\ufd3d\ufd50-\ufd8f\ufd92-\ufdc7\ufdf0-\ufdfb\ufe70-\ufe74\ufe76-\ufefc\uff21-\uff3a\uff41-\uff5a\uff66-\uffbe\uffc2-\uffc7\uffca-\uffcf\uffd2-\uffd7\uffda-\uffdc"
+let nonASCIIidentifierChars = "\u200c\u200d\xb7\u0300-\u036f\u0387\u0483-\u0487\u0591-\u05bd\u05bf\u05c1\u05c2\u05c4\u05c5\u05c7\u0610-\u061a\u064b-\u0669\u0670\u06d6-\u06dc\u06df-\u06e4\u06e7\u06e8\u06ea-\u06ed\u06f0-\u06f9\u0711\u0730-\u074a\u07a6-\u07b0\u07c0-\u07c9\u07eb-\u07f3\u0816-\u0819\u081b-\u0823\u0825-\u0827\u0829-\u082d\u0859-\u085b\u08d4-\u08e1\u08e3-\u0903\u093a-\u093c\u093e-\u094f\u0951-\u0957\u0962\u0963\u0966-\u096f\u0981-\u0983\u09bc\u09be-\u09c4\u09c7\u09c8\u09cb-\u09cd\u09d7\u09e2\u09e3\u09e6-\u09ef\u0a01-\u0a03\u0a3c\u0a3e-\u0a42\u0a47\u0a48\u0a4b-\u0a4d\u0a51\u0a66-\u0a71\u0a75\u0a81-\u0a83\u0abc\u0abe-\u0ac5\u0ac7-\u0ac9\u0acb-\u0acd\u0ae2\u0ae3\u0ae6-\u0aef\u0afa-\u0aff\u0b01-\u0b03\u0b3c\u0b3e-\u0b44\u0b47\u0b48\u0b4b-\u0b4d\u0b56\u0b57\u0b62\u0b63\u0b66-\u0b6f\u0b82\u0bbe-\u0bc2\u0bc6-\u0bc8\u0bca-\u0bcd\u0bd7\u0be6-\u0bef\u0c00-\u0c03\u0c3e-\u0c44\u0c46-\u0c48\u0c4a-\u0c4d\u0c55\u0c56\u0c62\u0c63\u0c66-\u0c6f\u0c81-\u0c83\u0cbc\u0cbe-\u0cc4\u0cc6-\u0cc8\u0cca-\u0ccd\u0cd5\u0cd6\u0ce2\u0ce3\u0ce6-\u0cef\u0d00-\u0d03\u0d3b\u0d3c\u0d3e-\u0d44\u0d46-\u0d48\u0d4a-\u0d4d\u0d57\u0d62\u0d63\u0d66-\u0d6f\u0d82\u0d83\u0dca\u0dcf-\u0dd4\u0dd6\u0dd8-\u0ddf\u0de6-\u0def\u0df2\u0df3\u0e31\u0e34-\u0e3a\u0e47-\u0e4e\u0e50-\u0e59\u0eb1\u0eb4-\u0eb9\u0ebb\u0ebc\u0ec8-\u0ecd\u0ed0-\u0ed9\u0f18\u0f19\u0f20-\u0f29\u0f35\u0f37\u0f39\u0f3e\u0f3f\u0f71-\u0f84\u0f86\u0f87\u0f8d-\u0f97\u0f99-\u0fbc\u0fc6\u102b-\u103e\u1040-\u1049\u1056-\u1059\u105e-\u1060\u1062-\u1064\u1067-\u106d\u1071-\u1074\u1082-\u108d\u108f-\u109d\u135d-\u135f\u1369-\u1371\u1712-\u1714\u1732-\u1734\u1752\u1753\u1772\u1773\u17b4-\u17d3\u17dd\u17e0-\u17e9\u180b-\u180d\u1810-\u1819\u18a9\u1920-\u192b\u1930-\u193b\u1946-\u194f\u19d0-\u19da\u1a17-\u1a1b\u1a55-\u1a5e\u1a60-\u1a7c\u1a7f-\u1a89\u1a90-\u1a99\u1ab0-\u1abd\u1b00-\u1b04\u1b34-\u1b44\u1b50-\u1b59\u1b6b-\u1b73\u1b80-\u1b82\u1ba1-\u1bad\u1bb0-\u1bb9\u1be6-\u1bf3\u1c24-\u1c37\u1c40-\u1c49\u1c50-\u1c59\u1cd0-\u1cd2\u1cd4-\u1ce8\u1ced\u1cf2-\u1cf4\u1cf7-\u1cf9\u1dc0-\u1df9\u1dfb-\u1dff\u203f\u2040\u2054\u20d0-\u20dc\u20e1\u20e5-\u20f0\u2cef-\u2cf1\u2d7f\u2de0-\u2dff\u302a-\u302f\u3099\u309a\ua620-\ua629\ua66f\ua674-\ua67d\ua69e\ua69f\ua6f0\ua6f1\ua802\ua806\ua80b\ua823-\ua827\ua880\ua881\ua8b4-\ua8c5\ua8d0-\ua8d9\ua8e0-\ua8f1\ua900-\ua909\ua926-\ua92d\ua947-\ua953\ua980-\ua983\ua9b3-\ua9c0\ua9d0-\ua9d9\ua9e5\ua9f0-\ua9f9\uaa29-\uaa36\uaa43\uaa4c\uaa4d\uaa50-\uaa59\uaa7b-\uaa7d\uaab0\uaab2-\uaab4\uaab7\uaab8\uaabe\uaabf\uaac1\uaaeb-\uaaef\uaaf5\uaaf6\uabe3-\uabea\uabec\uabed\uabf0-\uabf9\ufb1e\ufe00-\ufe0f\ufe20-\ufe2f\ufe33\ufe34\ufe4d-\ufe4f\uff10-\uff19\uff3f"
+
+const nonASCIIidentifierStart = new RegExp("[" + nonASCIIidentifierStartChars + "]")
+const nonASCIIidentifier = new RegExp("[" + nonASCIIidentifierStartChars + nonASCIIidentifierChars + "]")
+
+nonASCIIidentifierStartChars = nonASCIIidentifierChars = null
+
+// These are a run-length and offset encoded representation of the
+// >0xffff code points that are a valid part of identifiers. The
+// offset starts at 0x10000, and each pair of numbers represents an
+// offset to the next range, and then a size of the range. They were
+// generated by bin/generate-identifier-regex.js
+
+// eslint-disable-next-line comma-spacing
+const astralIdentifierStartCodes = [0,11,2,25,2,18,2,1,2,14,3,13,35,122,70,52,268,28,4,48,48,31,14,29,6,37,11,29,3,35,5,7,2,4,43,157,19,35,5,35,5,39,9,51,157,310,10,21,11,7,153,5,3,0,2,43,2,1,4,0,3,22,11,22,10,30,66,18,2,1,11,21,11,25,71,55,7,1,65,0,16,3,2,2,2,26,45,28,4,28,36,7,2,27,28,53,11,21,11,18,14,17,111,72,56,50,14,50,785,52,76,44,33,24,27,35,42,34,4,0,13,47,15,3,22,0,2,0,36,17,2,24,85,6,2,0,2,3,2,14,2,9,8,46,39,7,3,1,3,21,2,6,2,1,2,4,4,0,19,0,13,4,159,52,19,3,54,47,21,1,2,0,185,46,42,3,37,47,21,0,60,42,86,25,391,63,32,0,257,0,11,39,8,0,22,0,12,39,3,3,55,56,264,8,2,36,18,0,50,29,113,6,2,1,2,37,22,0,698,921,103,110,18,195,2749,1070,4050,582,8634,568,8,30,114,29,19,47,17,3,32,20,6,18,881,68,12,0,67,12,65,1,31,6124,20,754,9486,286,82,395,2309,106,6,12,4,8,8,9,5991,84,2,70,2,1,3,0,3,1,3,3,2,11,2,0,2,6,2,64,2,3,3,7,2,6,2,27,2,3,2,4,2,0,4,6,2,339,3,24,2,24,2,30,2,24,2,30,2,24,2,30,2,24,2,30,2,24,2,7,4149,196,60,67,1213,3,2,26,2,1,2,0,3,0,2,9,2,3,2,0,2,0,7,0,5,0,2,0,2,0,2,2,2,1,2,0,3,0,2,0,2,0,2,0,2,0,2,1,2,0,3,3,2,6,2,3,2,3,2,0,2,9,2,16,6,2,2,4,2,16,4421,42710,42,4148,12,221,3,5761,15,7472,3104,541]
+
+// eslint-disable-next-line comma-spacing
+const astralIdentifierCodes = [509,0,227,0,150,4,294,9,1368,2,2,1,6,3,41,2,5,0,166,1,1306,2,54,14,32,9,16,3,46,10,54,9,7,2,37,13,2,9,52,0,13,2,49,13,10,2,4,9,83,11,7,0,161,11,6,9,7,3,57,0,2,6,3,1,3,2,10,0,11,1,3,6,4,4,193,17,10,9,87,19,13,9,214,6,3,8,28,1,83,16,16,9,82,12,9,9,84,14,5,9,423,9,280,9,41,6,2,3,9,0,10,10,47,15,406,7,2,7,17,9,57,21,2,13,123,5,4,0,2,1,2,6,2,0,9,9,19719,9,135,4,60,6,26,9,1016,45,17,3,19723,1,5319,4,4,5,9,7,3,6,31,3,149,2,1418,49,513,54,5,49,9,0,15,0,23,4,2,14,1361,6,2,16,3,6,2,1,2,4,2214,6,110,6,6,9,792487,239]
+
+// This has a complexity linear to the value of the code. The
+// assumption is that looking up astral identifier characters is
+// rare.
+function isInAstralSet(code, set) {
+  let pos = 0x10000
+  for (let i = 0; i < set.length; i += 2) {
+    pos += set[i]
+    if (pos > code) return false
+    pos += set[i + 1]
+    if (pos >= code) return true
+  }
+}
+
+// Test whether a given character code starts an identifier.
+
+export function isIdentifierStart(code, astral) {
+  if (code < 65) return code === 36
+  if (code < 91) return true
+  if (code < 97) return code === 95
+  if (code < 123) return true
+  if (code <= 0xffff) return code >= 0xaa && nonASCIIidentifierStart.test(String.fromCharCode(code))
+  if (astral === false) return false
+  return isInAstralSet(code, astralIdentifierStartCodes)
+}
+
+// Test whether a given character is part of an identifier.
+
+export function isIdentifierChar(code, astral) {
+  if (code < 48) return code === 36
+  if (code < 58) return true
+  if (code < 65) return false
+  if (code < 91) return true
+  if (code < 97) return code === 95
+  if (code < 123) return true
+  if (code <= 0xffff) return code >= 0xaa && nonASCIIidentifier.test(String.fromCharCode(code))
+  if (astral === false) return false
+  return isInAstralSet(code, astralIdentifierStartCodes) || isInAstralSet(code, astralIdentifierCodes)
+}
diff --git a/tools/tests/apps/modules/imports/links/acorn/src/index.js b/tools/tests/apps/modules/imports/links/acorn/src/index.js
new file mode 100644
index 0000000000..aaf664da6b
--- /dev/null
+++ b/tools/tests/apps/modules/imports/links/acorn/src/index.js
@@ -0,0 +1,78 @@
+// Acorn is a tiny, fast JavaScript parser written in JavaScript.
+//
+// Acorn was written by Marijn Haverbeke, Ingvar Stepanyan, and
+// various contributors and released under an MIT license.
+//
+// Git repositories for Acorn are available at
+//
+//     http://marijnhaverbeke.nl/git/acorn
+//     https://github.com/acornjs/acorn.git
+//
+// Please use the [github bug tracker][ghbt] to report issues.
+//
+// [ghbt]: https://github.com/acornjs/acorn/issues
+//
+// This file defines the main parser interface. The library also comes
+// with a [error-tolerant parser][dammit] and an
+// [abstract syntax tree walker][walk], defined in other files.
+//
+// [dammit]: acorn_loose.js
+// [walk]: util/walk.js
+
+import {Parser} from "./state"
+import "./parseutil"
+import "./statement"
+import "./lval"
+import "./expression"
+import "./location"
+import "./scope"
+
+export {Parser, plugins} from "./state"
+export {defaultOptions} from "./options"
+export {Position, SourceLocation, getLineInfo} from "./locutil"
+export {Node} from "./node"
+export {TokenType, types as tokTypes, keywords as keywordTypes} from "./tokentype"
+export {TokContext, types as tokContexts} from "./tokencontext"
+export {isIdentifierChar, isIdentifierStart} from "./identifier"
+export {Token} from "./tokenize"
+export {isNewLine, lineBreak, lineBreakG, nonASCIIwhitespace} from "./whitespace"
+
+export const version = "5.5.3"
+
+// The main exported interface (under `self.acorn` when in the
+// browser) is a `parse` function that takes a code string and
+// returns an abstract syntax tree as specified by [Mozilla parser
+// API][api].
+//
+// [api]: https://developer.mozilla.org/en-US/docs/SpiderMonkey/Parser_API
+
+export function parse(input, options) {
+  return new Parser(options, input).parse()
+}
+
+// This function tries to parse a single expression at a given
+// offset in a string. Useful for parsing mixed-language formats
+// that embed JavaScript expressions.
+
+export function parseExpressionAt(input, pos, options) {
+  let p = new Parser(options, input, pos)
+  p.nextToken()
+  return p.parseExpression()
+}
+
+// Acorn is organized as a tokenizer and a recursive-descent parser.
+// The `tokenizer` export provides an interface to the tokenizer.
+
+export function tokenizer(input, options) {
+  return new Parser(options, input)
+}
+
+// This is a terrible kludge to support the existing, pre-ES6
+// interface where the loose parser module retroactively adds exports
+// to this module.
+export let parse_dammit, LooseParser, pluginsLoose // eslint-disable-line camelcase
+export function addLooseExports(parse, Parser, plugins) {
+  parse_dammit = parse // eslint-disable-line camelcase
+  LooseParser = Parser
+  pluginsLoose = plugins
+}
diff --git a/tools/tests/apps/modules/imports/links/acorn/src/location.js b/tools/tests/apps/modules/imports/links/acorn/src/location.js
new file mode 100644
index 0000000000..99e71234cc
--- /dev/null
+++ b/tools/tests/apps/modules/imports/links/acorn/src/location.js
@@ -0,0 +1,26 @@
+import {Parser} from "./state"
+import {Position, getLineInfo} from "./locutil"
+
+const pp = Parser.prototype
+
+// This function is used to raise exceptions on parse errors. It
+// takes an offset integer (into the current `input`) to indicate
+// the location of the error, attaches the position to the end
+// of the error message, and then raises a `SyntaxError` with that
+// message.
+
+pp.raise = function(pos, message) {
+  let loc = getLineInfo(this.input, pos)
+  message += " (" + loc.line + ":" + loc.column + ")"
+  let err = new SyntaxError(message)
+  err.pos = pos; err.loc = loc; err.raisedAt = this.pos
+  throw err
+}
+
+pp.raiseRecoverable = pp.raise
+
+pp.curPosition = function() {
+  if (this.options.locations) {
+    return new Position(this.curLine, this.pos - this.lineStart)
+  }
+}
diff --git a/tools/tests/apps/modules/imports/links/acorn/src/locutil.js b/tools/tests/apps/modules/imports/links/acorn/src/locutil.js
new file mode 100644
index 0000000000..5a9465e017
--- /dev/null
+++ b/tools/tests/apps/modules/imports/links/acorn/src/locutil.js
@@ -0,0 +1,42 @@
+import {lineBreakG} from "./whitespace"
+
+// These are used when `options.locations` is on, for the
+// `startLoc` and `endLoc` properties.
+
+export class Position {
+  constructor(line, col) {
+    this.line = line
+    this.column = col
+  }
+
+  offset(n) {
+    return new Position(this.line, this.column + n)
+  }
+}
+
+export class SourceLocation {
+  constructor(p, start, end) {
+    this.start = start
+    this.end = end
+    if (p.sourceFile !== null) this.source = p.sourceFile
+  }
+}
+
+// The `getLineInfo` function is mostly useful when the
+// `locations` option is off (for performance reasons) and you
+// want to find the line/column position for a given character
+// offset. `input` should be the code string that the offset refers
+// into.
+
+export function getLineInfo(input, offset) {
+  for (let line = 1, cur = 0;;) {
+    lineBreakG.lastIndex = cur
+    let match = lineBreakG.exec(input)
+    if (match && match.index < offset) {
+      ++line
+      cur = match.index + match[0].length
+    } else {
+      return new Position(line, offset - cur)
+    }
+  }
+}
diff --git a/tools/tests/apps/modules/imports/links/acorn/src/loose/expression.js b/tools/tests/apps/modules/imports/links/acorn/src/loose/expression.js
new file mode 100644
index 0000000000..b6c5ddbcb2
--- /dev/null
+++ b/tools/tests/apps/modules/imports/links/acorn/src/loose/expression.js
@@ -0,0 +1,582 @@
+import {LooseParser} from "./state"
+import {isDummy} from "./parseutil"
+import {tokTypes as tt} from "../index"
+
+const lp = LooseParser.prototype
+
+lp.checkLVal = function(expr) {
+  if (!expr) return expr
+  switch (expr.type) {
+  case "Identifier":
+  case "MemberExpression":
+    return expr
+
+  case "ParenthesizedExpression":
+    expr.expression = this.checkLVal(expr.expression)
+    return expr
+
+  default:
+    return this.dummyIdent()
+  }
+}
+
+lp.parseExpression = function(noIn) {
+  let start = this.storeCurrentPos()
+  let expr = this.parseMaybeAssign(noIn)
+  if (this.tok.type === tt.comma) {
+    let node = this.startNodeAt(start)
+    node.expressions = [expr]
+    while (this.eat(tt.comma)) node.expressions.push(this.parseMaybeAssign(noIn))
+    return this.finishNode(node, "SequenceExpression")
+  }
+  return expr
+}
+
+lp.parseParenExpression = function() {
+  this.pushCx()
+  this.expect(tt.parenL)
+  let val = this.parseExpression()
+  this.popCx()
+  this.expect(tt.parenR)
+  return val
+}
+
+lp.parseMaybeAssign = function(noIn) {
+  if (this.toks.isContextual("yield")) {
+    let node = this.startNode()
+    this.next()
+    if (this.semicolon() || this.canInsertSemicolon() || (this.tok.type != tt.star && !this.tok.type.startsExpr)) {
+      node.delegate = false
+      node.argument = null
+    } else {
+      node.delegate = this.eat(tt.star)
+      node.argument = this.parseMaybeAssign()
+    }
+    return this.finishNode(node, "YieldExpression")
+  }
+
+  let start = this.storeCurrentPos()
+  let left = this.parseMaybeConditional(noIn)
+  if (this.tok.type.isAssign) {
+    let node = this.startNodeAt(start)
+    node.operator = this.tok.value
+    node.left = this.tok.type === tt.eq ? this.toAssignable(left) : this.checkLVal(left)
+    this.next()
+    node.right = this.parseMaybeAssign(noIn)
+    return this.finishNode(node, "AssignmentExpression")
+  }
+  return left
+}
+
+lp.parseMaybeConditional = function(noIn) {
+  let start = this.storeCurrentPos()
+  let expr = this.parseExprOps(noIn)
+  if (this.eat(tt.question)) {
+    let node = this.startNodeAt(start)
+    node.test = expr
+    node.consequent = this.parseMaybeAssign()
+    node.alternate = this.expect(tt.colon) ? this.parseMaybeAssign(noIn) : this.dummyIdent()
+    return this.finishNode(node, "ConditionalExpression")
+  }
+  return expr
+}
+
+lp.parseExprOps = function(noIn) {
+  let start = this.storeCurrentPos()
+  let indent = this.curIndent, line = this.curLineStart
+  return this.parseExprOp(this.parseMaybeUnary(false), start, -1, noIn, indent, line)
+}
+
+lp.parseExprOp = function(left, start, minPrec, noIn, indent, line) {
+  if (this.curLineStart != line && this.curIndent < indent && this.tokenStartsLine()) return left
+  let prec = this.tok.type.binop
+  if (prec != null && (!noIn || this.tok.type !== tt._in)) {
+    if (prec > minPrec) {
+      let node = this.startNodeAt(start)
+      node.left = left
+      node.operator = this.tok.value
+      this.next()
+      if (this.curLineStart != line && this.curIndent < indent && this.tokenStartsLine()) {
+        node.right = this.dummyIdent()
+      } else {
+        let rightStart = this.storeCurrentPos()
+        node.right = this.parseExprOp(this.parseMaybeUnary(false), rightStart, prec, noIn, indent, line)
+      }
+      this.finishNode(node, /&&|\|\|/.test(node.operator) ? "LogicalExpression" : "BinaryExpression")
+      return this.parseExprOp(node, start, minPrec, noIn, indent, line)
+    }
+  }
+  return left
+}
+
+lp.parseMaybeUnary = function(sawUnary) {
+  let start = this.storeCurrentPos(), expr
+  if (this.options.ecmaVersion >= 8 && this.inAsync && this.toks.isContextual("await")) {
+    expr = this.parseAwait()
+    sawUnary = true
+  } else if (this.tok.type.prefix) {
+    let node = this.startNode(), update = this.tok.type === tt.incDec
+    if (!update) sawUnary = true
+    node.operator = this.tok.value
+    node.prefix = true
+    this.next()
+    node.argument = this.parseMaybeUnary(true)
+    if (update) node.argument = this.checkLVal(node.argument)
+    expr = this.finishNode(node, update ? "UpdateExpression" : "UnaryExpression")
+  } else if (this.tok.type === tt.ellipsis) {
+    let node = this.startNode()
+    this.next()
+    node.argument = this.parseMaybeUnary(sawUnary)
+    expr = this.finishNode(node, "SpreadElement")
+  } else {
+    expr = this.parseExprSubscripts()
+    while (this.tok.type.postfix && !this.canInsertSemicolon()) {
+      let node = this.startNodeAt(start)
+      node.operator = this.tok.value
+      node.prefix = false
+      node.argument = this.checkLVal(expr)
+      this.next()
+      expr = this.finishNode(node, "UpdateExpression")
+    }
+  }
+
+  if (!sawUnary && this.eat(tt.starstar)) {
+    let node = this.startNodeAt(start)
+    node.operator = "**"
+    node.left = expr
+    node.right = this.parseMaybeUnary(false)
+    return this.finishNode(node, "BinaryExpression")
+  }
+
+  return expr
+}
+
+lp.parseExprSubscripts = function() {
+  let start = this.storeCurrentPos()
+  return this.parseSubscripts(this.parseExprAtom(), start, false, this.curIndent, this.curLineStart)
+}
+
+lp.parseSubscripts = function(base, start, noCalls, startIndent, line) {
+  for (;;) {
+    if (this.curLineStart != line && this.curIndent <= startIndent && this.tokenStartsLine()) {
+      if (this.tok.type == tt.dot && this.curIndent == startIndent)
+        --startIndent
+      else
+        return base
+    }
+
+    let maybeAsyncArrow = base.type === "Identifier" && base.name === "async" && !this.canInsertSemicolon()
+
+    if (this.eat(tt.dot)) {
+      let node = this.startNodeAt(start)
+      node.object = base
+      if (this.curLineStart != line && this.curIndent <= startIndent && this.tokenStartsLine())
+        node.property = this.dummyIdent()
+      else
+        node.property = this.parsePropertyAccessor() || this.dummyIdent()
+      node.computed = false
+      base = this.finishNode(node, "MemberExpression")
+    } else if (this.tok.type == tt.bracketL) {
+      this.pushCx()
+      this.next()
+      let node = this.startNodeAt(start)
+      node.object = base
+      node.property = this.parseExpression()
+      node.computed = true
+      this.popCx()
+      this.expect(tt.bracketR)
+      base = this.finishNode(node, "MemberExpression")
+    } else if (!noCalls && this.tok.type == tt.parenL) {
+      let exprList = this.parseExprList(tt.parenR)
+      if (maybeAsyncArrow && this.eat(tt.arrow))
+        return this.parseArrowExpression(this.startNodeAt(start), exprList, true)
+      let node = this.startNodeAt(start)
+      node.callee = base
+      node.arguments = exprList
+      base = this.finishNode(node, "CallExpression")
+    } else if (this.tok.type == tt.backQuote) {
+      let node = this.startNodeAt(start)
+      node.tag = base
+      node.quasi = this.parseTemplate()
+      base = this.finishNode(node, "TaggedTemplateExpression")
+    } else {
+      return base
+    }
+  }
+}
+
+lp.parseExprAtom = function() {
+  let node
+  switch (this.tok.type) {
+  case tt._this:
+  case tt._super:
+    let type = this.tok.type === tt._this ? "ThisExpression" : "Super"
+    node = this.startNode()
+    this.next()
+    return this.finishNode(node, type)
+
+  case tt.name:
+    let start = this.storeCurrentPos()
+    let id = this.parseIdent()
+    let isAsync = false
+    if (id.name === "async" && !this.canInsertSemicolon()) {
+      if (this.eat(tt._function))
+        return this.parseFunction(this.startNodeAt(start), false, true)
+      if (this.tok.type === tt.name) {
+        id = this.parseIdent()
+        isAsync = true
+      }
+    }
+    return this.eat(tt.arrow) ? this.parseArrowExpression(this.startNodeAt(start), [id], isAsync) : id
+
+  case tt.regexp:
+    node = this.startNode()
+    let val = this.tok.value
+    node.regex = {pattern: val.pattern, flags: val.flags}
+    node.value = val.value
+    node.raw = this.input.slice(this.tok.start, this.tok.end)
+    this.next()
+    return this.finishNode(node, "Literal")
+
+  case tt.num: case tt.string:
+    node = this.startNode()
+    node.value = this.tok.value
+    node.raw = this.input.slice(this.tok.start, this.tok.end)
+    this.next()
+    return this.finishNode(node, "Literal")
+
+  case tt._null: case tt._true: case tt._false:
+    node = this.startNode()
+    node.value = this.tok.type === tt._null ? null : this.tok.type === tt._true
+    node.raw = this.tok.type.keyword
+    this.next()
+    return this.finishNode(node, "Literal")
+
+  case tt.parenL:
+    let parenStart = this.storeCurrentPos()
+    this.next()
+    let inner = this.parseExpression()
+    this.expect(tt.parenR)
+    if (this.eat(tt.arrow)) {
+      // (a,)=>a // SequenceExpression makes dummy in the last hole. Drop the dummy.
+      let params = inner.expressions || [inner]
+      if (params.length && isDummy(params[params.length - 1]))
+        params.pop()
+      return this.parseArrowExpression(this.startNodeAt(parenStart), params)
+    }
+    if (this.options.preserveParens) {
+      let par = this.startNodeAt(parenStart)
+      par.expression = inner
+      inner = this.finishNode(par, "ParenthesizedExpression")
+    }
+    return inner
+
+  case tt.bracketL:
+    node = this.startNode()
+    node.elements = this.parseExprList(tt.bracketR, true)
+    return this.finishNode(node, "ArrayExpression")
+
+  case tt.braceL:
+    return this.parseObj()
+
+  case tt._class:
+    return this.parseClass(false)
+
+  case tt._function:
+    node = this.startNode()
+    this.next()
+    return this.parseFunction(node, false)
+
+  case tt._new:
+    return this.parseNew()
+
+  case tt.backQuote:
+    return this.parseTemplate()
+
+  default:
+    return this.dummyIdent()
+  }
+}
+
+lp.parseNew = function() {
+  let node = this.startNode(), startIndent = this.curIndent, line = this.curLineStart
+  let meta = this.parseIdent(true)
+  if (this.options.ecmaVersion >= 6 && this.eat(tt.dot)) {
+    node.meta = meta
+    node.property = this.parseIdent(true)
+    return this.finishNode(node, "MetaProperty")
+  }
+  let start = this.storeCurrentPos()
+  node.callee = this.parseSubscripts(this.parseExprAtom(), start, true, startIndent, line)
+  if (this.tok.type == tt.parenL) {
+    node.arguments = this.parseExprList(tt.parenR)
+  } else {
+    node.arguments = []
+  }
+  return this.finishNode(node, "NewExpression")
+}
+
+lp.parseTemplateElement = function() {
+  let elem = this.startNode()
+
+  // The loose parser accepts invalid unicode escapes even in untagged templates.
+  if (this.tok.type === tt.invalidTemplate) {
+    elem.value = {
+      raw: this.tok.value,
+      cooked: null
+    }
+  } else {
+    elem.value = {
+      raw: this.input.slice(this.tok.start, this.tok.end).replace(/\r\n?/g, "\n"),
+      cooked: this.tok.value
+    }
+  }
+  this.next()
+  elem.tail = this.tok.type === tt.backQuote
+  return this.finishNode(elem, "TemplateElement")
+}
+
+lp.parseTemplate = function() {
+  let node = this.startNode()
+  this.next()
+  node.expressions = []
+  let curElt = this.parseTemplateElement()
+  node.quasis = [curElt]
+  while (!curElt.tail) {
+    this.next()
+    node.expressions.push(this.parseExpression())
+    if (this.expect(tt.braceR)) {
+      curElt = this.parseTemplateElement()
+    } else {
+      curElt = this.startNode()
+      curElt.value = {cooked: "", raw: ""}
+      curElt.tail = true
+      this.finishNode(curElt, "TemplateElement")
+    }
+    node.quasis.push(curElt)
+  }
+  this.expect(tt.backQuote)
+  return this.finishNode(node, "TemplateLiteral")
+}
+
+lp.parseObj = function() {
+  let node = this.startNode()
+  node.properties = []
+  this.pushCx()
+  let indent = this.curIndent + 1, line = this.curLineStart
+  this.eat(tt.braceL)
+  if (this.curIndent + 1 < indent) { indent = this.curIndent; line = this.curLineStart }
+  while (!this.closes(tt.braceR, indent, line)) {
+    let prop = this.startNode(), isGenerator, isAsync, start
+    if (this.options.ecmaVersion >= 9 && this.eat(tt.ellipsis)) {
+      prop.argument = this.parseMaybeAssign()
+      node.properties.push(this.finishNode(prop, "SpreadElement"))
+      this.eat(tt.comma)
+      continue
+    }
+    if (this.options.ecmaVersion >= 6) {
+      start = this.storeCurrentPos()
+      prop.method = false
+      prop.shorthand = false
+      isGenerator = this.eat(tt.star)
+    }
+    this.parsePropertyName(prop)
+    if (this.toks.isAsyncProp(prop)) {
+      isAsync = true
+      isGenerator = this.options.ecmaVersion >= 9 && this.eat(tt.star)
+      this.parsePropertyName(prop)
+    } else {
+      isAsync = false
+    }
+    if (isDummy(prop.key)) { if (isDummy(this.parseMaybeAssign())) this.next(); this.eat(tt.comma); continue }
+    if (this.eat(tt.colon)) {
+      prop.kind = "init"
+      prop.value = this.parseMaybeAssign()
+    } else if (this.options.ecmaVersion >= 6 && (this.tok.type === tt.parenL || this.tok.type === tt.braceL)) {
+      prop.kind = "init"
+      prop.method = true
+      prop.value = this.parseMethod(isGenerator, isAsync)
+    } else if (this.options.ecmaVersion >= 5 && prop.key.type === "Identifier" &&
+               !prop.computed && (prop.key.name === "get" || prop.key.name === "set") &&
+               (this.tok.type != tt.comma && this.tok.type != tt.braceR && this.tok.type != tt.eq)) {
+      prop.kind = prop.key.name
+      this.parsePropertyName(prop)
+      prop.value = this.parseMethod(false)
+    } else {
+      prop.kind = "init"
+      if (this.options.ecmaVersion >= 6) {
+        if (this.eat(tt.eq)) {
+          let assign = this.startNodeAt(start)
+          assign.operator = "="
+          assign.left = prop.key
+          assign.right = this.parseMaybeAssign()
+          prop.value = this.finishNode(assign, "AssignmentExpression")
+        } else {
+          prop.value = prop.key
+        }
+      } else {
+        prop.value = this.dummyIdent()
+      }
+      prop.shorthand = true
+    }
+    node.properties.push(this.finishNode(prop, "Property"))
+    this.eat(tt.comma)
+  }
+  this.popCx()
+  if (!this.eat(tt.braceR)) {
+    // If there is no closing brace, make the node span to the start
+    // of the next token (this is useful for Tern)
+    this.last.end = this.tok.start
+    if (this.options.locations) this.last.loc.end = this.tok.loc.start
+  }
+  return this.finishNode(node, "ObjectExpression")
+}
+
+lp.parsePropertyName = function(prop) {
+  if (this.options.ecmaVersion >= 6) {
+    if (this.eat(tt.bracketL)) {
+      prop.computed = true
+      prop.key = this.parseExpression()
+      this.expect(tt.bracketR)
+      return
+    } else {
+      prop.computed = false
+    }
+  }
+  let key = (this.tok.type === tt.num || this.tok.type === tt.string) ? this.parseExprAtom() : this.parseIdent()
+  prop.key = key || this.dummyIdent()
+}
+
+lp.parsePropertyAccessor = function() {
+  if (this.tok.type === tt.name || this.tok.type.keyword) return this.parseIdent()
+}
+
+lp.parseIdent = function() {
+  let name = this.tok.type === tt.name ? this.tok.value : this.tok.type.keyword
+  if (!name) return this.dummyIdent()
+  let node = this.startNode()
+  this.next()
+  node.name = name
+  return this.finishNode(node, "Identifier")
+}
+
+lp.initFunction = function(node) {
+  node.id = null
+  node.params = []
+  if (this.options.ecmaVersion >= 6) {
+    node.generator = false
+    node.expression = false
+  }
+  if (this.options.ecmaVersion >= 8)
+    node.async = false
+}
+
+// Convert existing expression atom to assignable pattern
+// if possible.
+
+lp.toAssignable = function(node, binding) {
+  if (!node || node.type == "Identifier" || (node.type == "MemberExpression" && !binding)) {
+    // Okay
+  } else if (node.type == "ParenthesizedExpression") {
+    this.toAssignable(node.expression, binding)
+  } else if (this.options.ecmaVersion < 6) {
+    return this.dummyIdent()
+  } else if (node.type == "ObjectExpression") {
+    node.type = "ObjectPattern"
+    for (let prop of node.properties)
+      this.toAssignable(prop, binding)
+  } else if (node.type == "ArrayExpression") {
+    node.type = "ArrayPattern"
+    this.toAssignableList(node.elements, binding)
+  } else if (node.type == "Property") {
+    this.toAssignable(node.value, binding)
+  } else if (node.type == "SpreadElement") {
+    node.type = "RestElement"
+    this.toAssignable(node.argument, binding)
+  } else if (node.type == "AssignmentExpression") {
+    node.type = "AssignmentPattern"
+    delete node.operator
+  } else {
+    return this.dummyIdent()
+  }
+  return node
+}
+
+lp.toAssignableList = function(exprList, binding) {
+  for (let expr of exprList)
+    this.toAssignable(expr, binding)
+  return exprList
+}
+
+lp.parseFunctionParams = function(params) {
+  params = this.parseExprList(tt.parenR)
+  return this.toAssignableList(params, true)
+}
+
+lp.parseMethod = function(isGenerator, isAsync) {
+  let node = this.startNode(), oldInAsync = this.inAsync
+  this.initFunction(node)
+  if (this.options.ecmaVersion >= 6)
+    node.generator = !!isGenerator
+  if (this.options.ecmaVersion >= 8)
+    node.async = !!isAsync
+  this.inAsync = node.async
+  node.params = this.parseFunctionParams()
+  node.body = this.parseBlock()
+  this.toks.adaptDirectivePrologue(node.body.body)
+  this.inAsync = oldInAsync
+  return this.finishNode(node, "FunctionExpression")
+}
+
+lp.parseArrowExpression = function(node, params, isAsync) {
+  let oldInAsync = this.inAsync
+  this.initFunction(node)
+  if (this.options.ecmaVersion >= 8)
+    node.async = !!isAsync
+  this.inAsync = node.async
+  node.params = this.toAssignableList(params, true)
+  node.expression = this.tok.type !== tt.braceL
+  if (node.expression) {
+    node.body = this.parseMaybeAssign()
+  } else {
+    node.body = this.parseBlock()
+    this.toks.adaptDirectivePrologue(node.body.body)
+  }
+  this.inAsync = oldInAsync
+  return this.finishNode(node, "ArrowFunctionExpression")
+}
+
+lp.parseExprList = function(close, allowEmpty) {
+  this.pushCx()
+  let indent = this.curIndent, line = this.curLineStart, elts = []
+  this.next() // Opening bracket
+  while (!this.closes(close, indent + 1, line)) {
+    if (this.eat(tt.comma)) {
+      elts.push(allowEmpty ? null : this.dummyIdent())
+      continue
+    }
+    let elt = this.parseMaybeAssign()
+    if (isDummy(elt)) {
+      if (this.closes(close, indent, line)) break
+      this.next()
+    } else {
+      elts.push(elt)
+    }
+    this.eat(tt.comma)
+  }
+  this.popCx()
+  if (!this.eat(close)) {
+    // If there is no closing brace, make the node span to the start
+    // of the next token (this is useful for Tern)
+    this.last.end = this.tok.start
+    if (this.options.locations) this.last.loc.end = this.tok.loc.start
+  }
+  return elts
+}
+
+lp.parseAwait = function() {
+  let node = this.startNode()
+  this.next()
+  node.argument = this.parseMaybeUnary()
+  return this.finishNode(node, "AwaitExpression")
+}
diff --git a/tools/tests/apps/modules/imports/links/acorn/src/loose/index.js b/tools/tests/apps/modules/imports/links/acorn/src/loose/index.js
new file mode 100644
index 0000000000..a698061a8b
--- /dev/null
+++ b/tools/tests/apps/modules/imports/links/acorn/src/loose/index.js
@@ -0,0 +1,47 @@
+// Acorn: Loose parser
+//
+// This module provides an alternative parser (`parse_dammit`) that
+// exposes that same interface as `parse`, but will try to parse
+// anything as JavaScript, repairing syntax error the best it can.
+// There are circumstances in which it will raise an error and give
+// up, but they are very rare. The resulting AST will be a mostly
+// valid JavaScript AST (as per the [Mozilla parser API][api], except
+// that:
+//
+// - Return outside functions is allowed
+//
+// - Label consistency (no conflicts, break only to existing labels)
+//   is not enforced.
+//
+// - Bogus Identifier nodes with a name of `"✖"` are inserted whenever
+//   the parser got too confused to return anything meaningful.
+//
+// [api]: https://developer.mozilla.org/en-US/docs/SpiderMonkey/Parser_API
+//
+// The expected use for this is to *first* try `acorn.parse`, and only
+// if that fails switch to `parse_dammit`. The loose parser might
+// parse badly indented code incorrectly, so **don't** use it as
+// your default parser.
+//
+// Quite a lot of acorn.js is duplicated here. The alternative was to
+// add a *lot* of extra cruft to that file, making it less readable
+// and slower. Copying and editing the code allowed me to make
+// invasive changes and simplifications without creating a complicated
+// tangle.
+
+import {addLooseExports, defaultOptions} from "../index"
+import {LooseParser, pluginsLoose} from "./state"
+import "./tokenize"
+import "./statement"
+import "./expression"
+
+export {LooseParser, pluginsLoose} from "./state"
+
+defaultOptions.tabSize = 4
+
+// eslint-disable-next-line camelcase
+export function parse_dammit(input, options) {
+  return new LooseParser(input, options).parse()
+}
+
+addLooseExports(parse_dammit, LooseParser, pluginsLoose)
diff --git a/tools/tests/apps/modules/imports/links/acorn/src/loose/parseutil.js b/tools/tests/apps/modules/imports/links/acorn/src/loose/parseutil.js
new file mode 100644
index 0000000000..b620fdaf0a
--- /dev/null
+++ b/tools/tests/apps/modules/imports/links/acorn/src/loose/parseutil.js
@@ -0,0 +1 @@
+export function isDummy(node) { return node.name == "✖" }
diff --git a/tools/tests/apps/modules/imports/links/acorn/src/loose/state.js b/tools/tests/apps/modules/imports/links/acorn/src/loose/state.js
new file mode 100644
index 0000000000..da068edb51
--- /dev/null
+++ b/tools/tests/apps/modules/imports/links/acorn/src/loose/state.js
@@ -0,0 +1,170 @@
+import {tokenizer, SourceLocation, tokTypes as tt, Node, lineBreak, isNewLine} from "../index"
+
+function noop() {}
+
+// Registered plugins
+export const pluginsLoose = {}
+
+export class LooseParser {
+  constructor(input, options = {}) {
+    this.toks = tokenizer(input, options)
+    this.options = this.toks.options
+    this.input = this.toks.input
+    this.tok = this.last = {type: tt.eof, start: 0, end: 0}
+    this.tok.validateRegExpFlags = noop
+    this.tok.validateRegExpPattern = noop
+    if (this.options.locations) {
+      let here = this.toks.curPosition()
+      this.tok.loc = new SourceLocation(this.toks, here, here)
+    }
+    this.ahead = [] // Tokens ahead
+    this.context = [] // Indentation contexted
+    this.curIndent = 0
+    this.curLineStart = 0
+    this.nextLineStart = this.lineEnd(this.curLineStart) + 1
+    this.inAsync = false
+    // Load plugins
+    this.options.pluginsLoose = options.pluginsLoose || {}
+    this.loadPlugins(this.options.pluginsLoose)
+  }
+
+  startNode() {
+    return new Node(this.toks, this.tok.start, this.options.locations ? this.tok.loc.start : null)
+  }
+
+  storeCurrentPos() {
+    return this.options.locations ? [this.tok.start, this.tok.loc.start] : this.tok.start
+  }
+
+  startNodeAt(pos) {
+    if (this.options.locations) {
+      return new Node(this.toks, pos[0], pos[1])
+    } else {
+      return new Node(this.toks, pos)
+    }
+  }
+
+  finishNode(node, type) {
+    node.type = type
+    node.end = this.last.end
+    if (this.options.locations)
+      node.loc.end = this.last.loc.end
+    if (this.options.ranges)
+      node.range[1] = this.last.end
+    return node
+  }
+
+  dummyNode(type) {
+    let dummy = this.startNode()
+    dummy.type = type
+    dummy.end = dummy.start
+    if (this.options.locations)
+      dummy.loc.end = dummy.loc.start
+    if (this.options.ranges)
+      dummy.range[1] = dummy.start
+    this.last = {type: tt.name, start: dummy.start, end: dummy.start, loc: dummy.loc}
+    return dummy
+  }
+
+  dummyIdent() {
+    let dummy = this.dummyNode("Identifier")
+    dummy.name = "✖"
+    return dummy
+  }
+
+  dummyString() {
+    let dummy = this.dummyNode("Literal")
+    dummy.value = dummy.raw = "✖"
+    return dummy
+  }
+
+  eat(type) {
+    if (this.tok.type === type) {
+      this.next()
+      return true
+    } else {
+      return false
+    }
+  }
+
+  isContextual(name) {
+    return this.tok.type === tt.name && this.tok.value === name
+  }
+
+  eatContextual(name) {
+    return this.tok.value === name && this.eat(tt.name)
+  }
+
+  canInsertSemicolon() {
+    return this.tok.type === tt.eof || this.tok.type === tt.braceR ||
+      lineBreak.test(this.input.slice(this.last.end, this.tok.start))
+  }
+
+  semicolon() {
+    return this.eat(tt.semi)
+  }
+
+  expect(type) {
+    if (this.eat(type)) return true
+    for (let i = 1; i <= 2; i++) {
+      if (this.lookAhead(i).type == type) {
+        for (let j = 0; j < i; j++) this.next()
+        return true
+      }
+    }
+  }
+
+  pushCx() {
+    this.context.push(this.curIndent)
+  }
+
+  popCx() {
+    this.curIndent = this.context.pop()
+  }
+
+  lineEnd(pos) {
+    while (pos < this.input.length && !isNewLine(this.input.charCodeAt(pos))) ++pos
+    return pos
+  }
+
+  indentationAfter(pos) {
+    for (let count = 0;; ++pos) {
+      let ch = this.input.charCodeAt(pos)
+      if (ch === 32) ++count
+      else if (ch === 9) count += this.options.tabSize
+      else return count
+    }
+  }
+
+  closes(closeTok, indent, line, blockHeuristic) {
+    if (this.tok.type === closeTok || this.tok.type === tt.eof) return true
+    return line != this.curLineStart && this.curIndent < indent && this.tokenStartsLine() &&
+      (!blockHeuristic || this.nextLineStart >= this.input.length ||
+       this.indentationAfter(this.nextLineStart) < indent)
+  }
+
+  tokenStartsLine() {
+    for (let p = this.tok.start - 1; p >= this.curLineStart; --p) {
+      let ch = this.input.charCodeAt(p)
+      if (ch !== 9 && ch !== 32) return false
+    }
+    return true
+  }
+
+  extend(name, f) {
+    this[name] = f(this[name])
+  }
+
+  loadPlugins(pluginConfigs) {
+    for (let name in pluginConfigs) {
+      let plugin = pluginsLoose[name]
+      if (!plugin) throw new Error("Plugin '" + name + "' not found")
+      plugin(this, pluginConfigs[name])
+    }
+  }
+
+  parse() {
+    this.next()
+    return this.parseTopLevel()
+  }
+}
diff --git a/tools/tests/apps/modules/imports/links/acorn/src/loose/statement.js b/tools/tests/apps/modules/imports/links/acorn/src/loose/statement.js
new file mode 100644
index 0000000000..aa30696c41
--- /dev/null
+++ b/tools/tests/apps/modules/imports/links/acorn/src/loose/statement.js
@@ -0,0 +1,459 @@
+import {LooseParser} from "./state"
+import {isDummy} from "./parseutil"
+import {getLineInfo, tokTypes as tt} from "../index"
+
+const lp = LooseParser.prototype
+
+lp.parseTopLevel = function() {
+  let node = this.startNodeAt(this.options.locations ? [0, getLineInfo(this.input, 0)] : 0)
+  node.body = []
+  while (this.tok.type !== tt.eof) node.body.push(this.parseStatement())
+  this.toks.adaptDirectivePrologue(node.body)
+  this.last = this.tok
+  if (this.options.ecmaVersion >= 6) {
+    node.sourceType = this.options.sourceType
+  }
+  return this.finishNode(node, "Program")
+}
+
+lp.parseStatement = function() {
+  let starttype = this.tok.type, node = this.startNode(), kind
+
+  if (this.toks.isLet()) {
+    starttype = tt._var
+    kind = "let"
+  }
+
+  switch (starttype) {
+  case tt._break: case tt._continue:
+    this.next()
+    let isBreak = starttype === tt._break
+    if (this.semicolon() || this.canInsertSemicolon()) {
+      node.label = null
+    } else {
+      node.label = this.tok.type === tt.name ? this.parseIdent() : null
+      this.semicolon()
+    }
+    return this.finishNode(node, isBreak ? "BreakStatement" : "ContinueStatement")
+
+  case tt._debugger:
+    this.next()
+    this.semicolon()
+    return this.finishNode(node, "DebuggerStatement")
+
+  case tt._do:
+    this.next()
+    node.body = this.parseStatement()
+    node.test = this.eat(tt._while) ? this.parseParenExpression() : this.dummyIdent()
+    this.semicolon()
+    return this.finishNode(node, "DoWhileStatement")
+
+  case tt._for:
+    this.next() // `for` keyword
+    let isAwait = this.options.ecmaVersion >= 9 && this.inAsync && this.eatContextual("await")
+
+    this.pushCx()
+    this.expect(tt.parenL)
+    if (this.tok.type === tt.semi) return this.parseFor(node, null)
+    let isLet = this.toks.isLet()
+    if (isLet || this.tok.type === tt._var || this.tok.type === tt._const) {
+      let init = this.parseVar(true, isLet ? "let" : this.tok.value)
+      if (init.declarations.length === 1 && (this.tok.type === tt._in || this.isContextual("of"))) {
+        if (this.options.ecmaVersion >= 9 && this.tok.type !== tt._in) {
+          node.await = isAwait
+        }
+        return this.parseForIn(node, init)
+      }
+      return this.parseFor(node, init)
+    }
+    let init = this.parseExpression(true)
+    if (this.tok.type === tt._in || this.isContextual("of")) {
+      if (this.options.ecmaVersion >= 9 && this.tok.type !== tt._in) {
+        node.await = isAwait
+      }
+      return this.parseForIn(node, this.toAssignable(init))
+    }
+    return this.parseFor(node, init)
+
+  case tt._function:
+    this.next()
+    return this.parseFunction(node, true)
+
+  case tt._if:
+    this.next()
+    node.test = this.parseParenExpression()
+    node.consequent = this.parseStatement()
+    node.alternate = this.eat(tt._else) ? this.parseStatement() : null
+    return this.finishNode(node, "IfStatement")
+
+  case tt._return:
+    this.next()
+    if (this.eat(tt.semi) || this.canInsertSemicolon()) node.argument = null
+    else { node.argument = this.parseExpression(); this.semicolon() }
+    return this.finishNode(node, "ReturnStatement")
+
+  case tt._switch:
+    let blockIndent = this.curIndent, line = this.curLineStart
+    this.next()
+    node.discriminant = this.parseParenExpression()
+    node.cases = []
+    this.pushCx()
+    this.expect(tt.braceL)
+
+    let cur
+    while (!this.closes(tt.braceR, blockIndent, line, true)) {
+      if (this.tok.type === tt._case || this.tok.type === tt._default) {
+        let isCase = this.tok.type === tt._case
+        if (cur) this.finishNode(cur, "SwitchCase")
+        node.cases.push(cur = this.startNode())
+        cur.consequent = []
+        this.next()
+        if (isCase) cur.test = this.parseExpression()
+        else cur.test = null
+        this.expect(tt.colon)
+      } else {
+        if (!cur) {
+          node.cases.push(cur = this.startNode())
+          cur.consequent = []
+          cur.test = null
+        }
+        cur.consequent.push(this.parseStatement())
+      }
+    }
+    if (cur) this.finishNode(cur, "SwitchCase")
+    this.popCx()
+    this.eat(tt.braceR)
+    return this.finishNode(node, "SwitchStatement")
+
+  case tt._throw:
+    this.next()
+    node.argument = this.parseExpression()
+    this.semicolon()
+    return this.finishNode(node, "ThrowStatement")
+
+  case tt._try:
+    this.next()
+    node.block = this.parseBlock()
+    node.handler = null
+    if (this.tok.type === tt._catch) {
+      let clause = this.startNode()
+      this.next()
+      this.expect(tt.parenL)
+      clause.param = this.toAssignable(this.parseExprAtom(), true)
+      this.expect(tt.parenR)
+      clause.body = this.parseBlock()
+      node.handler = this.finishNode(clause, "CatchClause")
+    }
+    node.finalizer = this.eat(tt._finally) ? this.parseBlock() : null
+    if (!node.handler && !node.finalizer) return node.block
+    return this.finishNode(node, "TryStatement")
+
+  case tt._var:
+  case tt._const:
+    return this.parseVar(false, kind || this.tok.value)
+
+  case tt._while:
+    this.next()
+    node.test = this.parseParenExpression()
+    node.body = this.parseStatement()
+    return this.finishNode(node, "WhileStatement")
+
+  case tt._with:
+    this.next()
+    node.object = this.parseParenExpression()
+    node.body = this.parseStatement()
+    return this.finishNode(node, "WithStatement")
+
+  case tt.braceL:
+    return this.parseBlock()
+
+  case tt.semi:
+    this.next()
+    return this.finishNode(node, "EmptyStatement")
+
+  case tt._class:
+    return this.parseClass(true)
+
+  case tt._import:
+    return this.parseImport()
+
+  case tt._export:
+    return this.parseExport()
+
+  default:
+    if (this.toks.isAsyncFunction()) {
+      this.next()
+      this.next()
+      return this.parseFunction(node, true, true)
+    }
+    let expr = this.parseExpression()
+    if (isDummy(expr)) {
+      this.next()
+      if (this.tok.type === tt.eof) return this.finishNode(node, "EmptyStatement")
+      return this.parseStatement()
+    } else if (starttype === tt.name && expr.type === "Identifier" && this.eat(tt.colon)) {
+      node.body = this.parseStatement()
+      node.label = expr
+      return this.finishNode(node, "LabeledStatement")
+    } else {
+      node.expression = expr
+      this.semicolon()
+      return this.finishNode(node, "ExpressionStatement")
+    }
+  }
+}
+
+lp.parseBlock = function() {
+  let node = this.startNode()
+  this.pushCx()
+  this.expect(tt.braceL)
+  let blockIndent = this.curIndent, line = this.curLineStart
+  node.body = []
+  while (!this.closes(tt.braceR, blockIndent, line, true))
+    node.body.push(this.parseStatement())
+  this.popCx()
+  this.eat(tt.braceR)
+  return this.finishNode(node, "BlockStatement")
+}
+
+lp.parseFor = function(node, init) {
+  node.init = init
+  node.test = node.update = null
+  if (this.eat(tt.semi) && this.tok.type !== tt.semi) node.test = this.parseExpression()
+  if (this.eat(tt.semi) && this.tok.type !== tt.parenR) node.update = this.parseExpression()
+  this.popCx()
+  this.expect(tt.parenR)
+  node.body = this.parseStatement()
+  return this.finishNode(node, "ForStatement")
+}
+
+lp.parseForIn = function(node, init) {
+  let type = this.tok.type === tt._in ? "ForInStatement" : "ForOfStatement"
+  this.next()
+  node.left = init
+  node.right = this.parseExpression()
+  this.popCx()
+  this.expect(tt.parenR)
+  node.body = this.parseStatement()
+  return this.finishNode(node, type)
+}
+
+lp.parseVar = function(noIn, kind) {
+  let node = this.startNode()
+  node.kind = kind
+  this.next()
+  node.declarations = []
+  do {
+    let decl = this.startNode()
+    decl.id = this.options.ecmaVersion >= 6 ? this.toAssignable(this.parseExprAtom(), true) : this.parseIdent()
+    decl.init = this.eat(tt.eq) ? this.parseMaybeAssign(noIn) : null
+    node.declarations.push(this.finishNode(decl, "VariableDeclarator"))
+  } while (this.eat(tt.comma))
+  if (!node.declarations.length) {
+    let decl = this.startNode()
+    decl.id = this.dummyIdent()
+    node.declarations.push(this.finishNode(decl, "VariableDeclarator"))
+  }
+  if (!noIn) this.semicolon()
+  return this.finishNode(node, "VariableDeclaration")
+}
+
+lp.parseClass = function(isStatement) {
+  let node = this.startNode()
+  this.next()
+  if (this.tok.type === tt.name) node.id = this.parseIdent()
+  else if (isStatement === true) node.id = this.dummyIdent()
+  else node.id = null
+  node.superClass = this.eat(tt._extends) ? this.parseExpression() : null
+  node.body = this.startNode()
+  node.body.body = []
+  this.pushCx()
+  let indent = this.curIndent + 1, line = this.curLineStart
+  this.eat(tt.braceL)
+  if (this.curIndent + 1 < indent) { indent = this.curIndent; line = this.curLineStart }
+  while (!this.closes(tt.braceR, indent, line)) {
+    if (this.semicolon()) continue
+    let method = this.startNode(), isGenerator, isAsync
+    if (this.options.ecmaVersion >= 6) {
+      method.static = false
+      isGenerator = this.eat(tt.star)
+    }
+    this.parsePropertyName(method)
+    if (isDummy(method.key)) { if (isDummy(this.parseMaybeAssign())) this.next(); this.eat(tt.comma); continue }
+    if (method.key.type === "Identifier" && !method.computed && method.key.name === "static" &&
+        (this.tok.type != tt.parenL && this.tok.type != tt.braceL)) {
+      method.static = true
+      isGenerator = this.eat(tt.star)
+      this.parsePropertyName(method)
+    } else {
+      method.static = false
+    }
+    if (!method.computed &&
+        method.key.type === "Identifier" && method.key.name === "async" && this.tok.type !== tt.parenL &&
+        !this.canInsertSemicolon()) {
+      isAsync = true
+      isGenerator = this.options.ecmaVersion >= 9 && this.eat(tt.star)
+      this.parsePropertyName(method)
+    } else {
+      isAsync = false
+    }
+    if (this.options.ecmaVersion >= 5 && method.key.type === "Identifier" &&
+        !method.computed && (method.key.name === "get" || method.key.name === "set") &&
+        this.tok.type !== tt.parenL && this.tok.type !== tt.braceL) {
+      method.kind = method.key.name
+      this.parsePropertyName(method)
+      method.value = this.parseMethod(false)
+    } else {
+      if (!method.computed && !method.static && !isGenerator && !isAsync && (
+        method.key.type === "Identifier" && method.key.name === "constructor" ||
+          method.key.type === "Literal" && method.key.value === "constructor")) {
+        method.kind = "constructor"
+      } else {
+        method.kind = "method"
+      }
+      method.value = this.parseMethod(isGenerator, isAsync)
+    }
+    node.body.body.push(this.finishNode(method, "MethodDefinition"))
+  }
+  this.popCx()
+  if (!this.eat(tt.braceR)) {
+    // If there is no closing brace, make the node span to the start
+    // of the next token (this is useful for Tern)
+    this.last.end = this.tok.start
+    if (this.options.locations) this.last.loc.end = this.tok.loc.start
+  }
+  this.semicolon()
+  this.finishNode(node.body, "ClassBody")
+  return this.finishNode(node, isStatement ? "ClassDeclaration" : "ClassExpression")
+}
+
+lp.parseFunction = function(node, isStatement, isAsync) {
+  let oldInAsync = this.inAsync
+  this.initFunction(node)
+  if (this.options.ecmaVersion >= 6) {
+    node.generator = this.eat(tt.star)
+  }
+  if (this.options.ecmaVersion >= 8) {
+    node.async = !!isAsync
+  }
+  if (this.tok.type === tt.name) node.id = this.parseIdent()
+  else if (isStatement === true) node.id = this.dummyIdent()
+  this.inAsync = node.async
+  node.params = this.parseFunctionParams()
+  node.body = this.parseBlock()
+  this.toks.adaptDirectivePrologue(node.body.body)
+  this.inAsync = oldInAsync
+  return this.finishNode(node, isStatement ? "FunctionDeclaration" : "FunctionExpression")
+}
+
+lp.parseExport = function() {
+  let node = this.startNode()
+  this.next()
+  if (this.eat(tt.star)) {
+    node.source = this.eatContextual("from") ? this.parseExprAtom() : this.dummyString()
+    return this.finishNode(node, "ExportAllDeclaration")
+  }
+  if (this.eat(tt._default)) {
+    // export default (function foo() {}) // This is FunctionExpression.
+    let isAsync
+    if (this.tok.type === tt._function || (isAsync = this.toks.isAsyncFunction())) {
+      let fNode = this.startNode()
+      this.next()
+      if (isAsync) this.next()
+      node.declaration = this.parseFunction(fNode, "nullableID", isAsync)
+    } else if (this.tok.type === tt._class) {
+      node.declaration = this.parseClass("nullableID")
+    } else {
+      node.declaration = this.parseMaybeAssign()
+      this.semicolon()
+    }
+    return this.finishNode(node, "ExportDefaultDeclaration")
+  }
+  if (this.tok.type.keyword || this.toks.isLet() || this.toks.isAsyncFunction()) {
+    node.declaration = this.parseStatement()
+    node.specifiers = []
+    node.source = null
+  } else {
+    node.declaration = null
+    node.specifiers = this.parseExportSpecifierList()
+    node.source = this.eatContextual("from") ? this.parseExprAtom() : null
+    this.semicolon()
+  }
+  return this.finishNode(node, "ExportNamedDeclaration")
+}
+
+lp.parseImport = function() {
+  let node = this.startNode()
+  this.next()
+  if (this.tok.type === tt.string) {
+    node.specifiers = []
+    node.source = this.parseExprAtom()
+  } else {
+    let elt
+    if (this.tok.type === tt.name && this.tok.value !== "from") {
+      elt = this.startNode()
+      elt.local = this.parseIdent()
+      this.finishNode(elt, "ImportDefaultSpecifier")
+      this.eat(tt.comma)
+    }
+    node.specifiers = this.parseImportSpecifierList()
+    node.source = this.eatContextual("from") && this.tok.type == tt.string ? this.parseExprAtom() : this.dummyString()
+    if (elt) node.specifiers.unshift(elt)
+  }
+  this.semicolon()
+  return this.finishNode(node, "ImportDeclaration")
+}
+
+lp.parseImportSpecifierList = function() {
+  let elts = []
+  if (this.tok.type === tt.star) {
+    let elt = this.startNode()
+    this.next()
+    elt.local = this.eatContextual("as") ? this.parseIdent() : this.dummyIdent()
+    elts.push(this.finishNode(elt, "ImportNamespaceSpecifier"))
+  } else {
+    let indent = this.curIndent, line = this.curLineStart, continuedLine = this.nextLineStart
+    this.pushCx()
+    this.eat(tt.braceL)
+    if (this.curLineStart > continuedLine) continuedLine = this.curLineStart
+    while (!this.closes(tt.braceR, indent + (this.curLineStart <= continuedLine ? 1 : 0), line)) {
+      let elt = this.startNode()
+      if (this.eat(tt.star)) {
+        elt.local = this.eatContextual("as") ? this.parseIdent() : this.dummyIdent()
+        this.finishNode(elt, "ImportNamespaceSpecifier")
+      } else {
+        if (this.isContextual("from")) break
+        elt.imported = this.parseIdent()
+        if (isDummy(elt.imported)) break
+        elt.local = this.eatContextual("as") ? this.parseIdent() : elt.imported
+        this.finishNode(elt, "ImportSpecifier")
+      }
+      elts.push(elt)
+      this.eat(tt.comma)
+    }
+    this.eat(tt.braceR)
+    this.popCx()
+  }
+  return elts
+}
+
+lp.parseExportSpecifierList = function() {
+  let elts = []
+  let indent = this.curIndent, line = this.curLineStart, continuedLine = this.nextLineStart
+  this.pushCx()
+  this.eat(tt.braceL)
+  if (this.curLineStart > continuedLine) continuedLine = this.curLineStart
+  while (!this.closes(tt.braceR, indent + (this.curLineStart <= continuedLine ? 1 : 0), line)) {
+    if (this.isContextual("from")) break
+    let elt = this.startNode()
+    elt.local = this.parseIdent()
+    if (isDummy(elt.local)) break
+    elt.exported = this.eatContextual("as") ? this.parseIdent() : elt.local
+    this.finishNode(elt, "ExportSpecifier")
+    elts.push(elt)
+    this.eat(tt.comma)
+  }
+  this.eat(tt.braceR)
+  this.popCx()
+  return elts
+}
diff --git a/tools/tests/apps/modules/imports/links/acorn/src/loose/tokenize.js b/tools/tests/apps/modules/imports/links/acorn/src/loose/tokenize.js
new file mode 100644
index 0000000000..619b6ee9e4
--- /dev/null
+++ b/tools/tests/apps/modules/imports/links/acorn/src/loose/tokenize.js
@@ -0,0 +1,111 @@
+import {tokTypes as tt, Token, isNewLine, SourceLocation, getLineInfo, lineBreakG} from "../index"
+import {LooseParser} from "./state"
+
+const lp = LooseParser.prototype
+
+function isSpace(ch) {
+  return (ch < 14 && ch > 8) || ch === 32 || ch === 160 || isNewLine(ch)
+}
+
+lp.next = function() {
+  this.last = this.tok
+  if (this.ahead.length)
+    this.tok = this.ahead.shift()
+  else
+    this.tok = this.readToken()
+
+  if (this.tok.start >= this.nextLineStart) {
+    while (this.tok.start >= this.nextLineStart) {
+      this.curLineStart = this.nextLineStart
+      this.nextLineStart = this.lineEnd(this.curLineStart) + 1
+    }
+    this.curIndent = this.indentationAfter(this.curLineStart)
+  }
+}
+
+lp.readToken = function() {
+  for (;;) {
+    try {
+      this.toks.next()
+      if (this.toks.type === tt.dot &&
+          this.input.substr(this.toks.end, 1) === "." &&
+          this.options.ecmaVersion >= 6) {
+        this.toks.end++
+        this.toks.type = tt.ellipsis
+      }
+      return new Token(this.toks)
+    } catch (e) {
+      if (!(e instanceof SyntaxError)) throw e
+
+      // Try to skip some text, based on the error message, and then continue
+      let msg = e.message, pos = e.raisedAt, replace = true
+      if (/unterminated/i.test(msg)) {
+        pos = this.lineEnd(e.pos + 1)
+        if (/string/.test(msg)) {
+          replace = {start: e.pos, end: pos, type: tt.string, value: this.input.slice(e.pos + 1, pos)}
+        } else if (/regular expr/i.test(msg)) {
+          let re = this.input.slice(e.pos, pos)
+          try { re = new RegExp(re) } catch (e) { /* ignore compilation error due to new syntax */ }
+          replace = {start: e.pos, end: pos, type: tt.regexp, value: re}
+        } else if (/template/.test(msg)) {
+          replace = {
+            start: e.pos,
+            end: pos,
+            type: tt.template,
+            value: this.input.slice(e.pos, pos)
+          }
+        } else {
+          replace = false
+        }
+      } else if (/invalid (unicode|regexp|number)|expecting unicode|octal literal|is reserved|directly after number|expected number in radix/i.test(msg)) {
+        while (pos < this.input.length && !isSpace(this.input.charCodeAt(pos))) ++pos
+      } else if (/character escape|expected hexadecimal/i.test(msg)) {
+        while (pos < this.input.length) {
+          let ch = this.input.charCodeAt(pos++)
+          if (ch === 34 || ch === 39 || isNewLine(ch)) break
+        }
+      } else if (/unexpected character/i.test(msg)) {
+        pos++
+        replace = false
+      } else if (/regular expression/i.test(msg)) {
+        replace = true
+      } else {
+        throw e
+      }
+      this.resetTo(pos)
+      if (replace === true) replace = {start: pos, end: pos, type: tt.name, value: "✖"}
+      if (replace) {
+        if (this.options.locations)
+          replace.loc = new SourceLocation(
+            this.toks,
+            getLineInfo(this.input, replace.start),
+            getLineInfo(this.input, replace.end))
+        return replace
+      }
+    }
+  }
+}
+
+lp.resetTo = function(pos) {
+  this.toks.pos = pos
+  let ch = this.input.charAt(pos - 1)
+  this.toks.exprAllowed = !ch || /[[{(,;:?/*=+\-~!|&%^<>]/.test(ch) ||
+    /[enwfd]/.test(ch) &&
+    /\b(case|else|return|throw|new|in|(instance|type)?of|delete|void)$/.test(this.input.slice(pos - 10, pos))
+
+  if (this.options.locations) {
+    this.toks.curLine = 1
+    this.toks.lineStart = lineBreakG.lastIndex = 0
+    let match
+    while ((match = lineBreakG.exec(this.input)) && match.index < pos) {
+      ++this.toks.curLine
+      this.toks.lineStart = match.index + match[0].length
+    }
+  }
+}
+
+lp.lookAhead = function(n) {
+  while (n > this.ahead.length)
+    this.ahead.push(this.readToken())
+  return this.ahead[n - 1]
+}
diff --git a/tools/tests/apps/modules/imports/links/acorn/src/lval.js b/tools/tests/apps/modules/imports/links/acorn/src/lval.js
new file mode 100644
index 0000000000..0fc1bc5284
--- /dev/null
+++ b/tools/tests/apps/modules/imports/links/acorn/src/lval.js
@@ -0,0 +1,248 @@
+import {types as tt} from "./tokentype"
+import {Parser} from "./state"
+import {has} from "./util"
+
+const pp = Parser.prototype
+
+// Convert existing expression atom to assignable pattern
+// if possible.
+
+pp.toAssignable = function(node, isBinding, refDestructuringErrors) {
+  if (this.options.ecmaVersion >= 6 && node) {
+    switch (node.type) {
+    case "Identifier":
+      if (this.inAsync && node.name === "await")
+        this.raise(node.start, "Can not use 'await' as identifier inside an async function")
+      break
+
+    case "ObjectPattern":
+    case "ArrayPattern":
+    case "RestElement":
+      break
+
+    case "ObjectExpression":
+      node.type = "ObjectPattern"
+      if (refDestructuringErrors) this.checkPatternErrors(refDestructuringErrors, true)
+      for (let prop of node.properties) {
+        this.toAssignable(prop, isBinding)
+        // Early error:
+        //   AssignmentRestProperty[Yield, Await] :
+        //     `...` DestructuringAssignmentTarget[Yield, Await]
+        //
+        //   It is a Syntax Error if |DestructuringAssignmentTarget| is an |ArrayLiteral| or an |ObjectLiteral|.
+        if (
+          prop.type === "RestElement" &&
+          (prop.argument.type === "ArrayPattern" || prop.argument.type === "ObjectPattern")
+        ) {
+          this.raise(prop.argument.start, "Unexpected token")
+        }
+      }
+      break
+
+    case "Property":
+      // AssignmentProperty has type == "Property"
+      if (node.kind !== "init") this.raise(node.key.start, "Object pattern can't contain getter or setter")
+      this.toAssignable(node.value, isBinding)
+      break
+
+    case "ArrayExpression":
+      node.type = "ArrayPattern"
+      if (refDestructuringErrors) this.checkPatternErrors(refDestructuringErrors, true)
+      this.toAssignableList(node.elements, isBinding)
+      break
+
+    case "SpreadElement":
+      node.type = "RestElement"
+      this.toAssignable(node.argument, isBinding)
+      if (node.argument.type === "AssignmentPattern")
+        this.raise(node.argument.start, "Rest elements cannot have a default value")
+      break
+
+    case "AssignmentExpression":
+      if (node.operator !== "=") this.raise(node.left.end, "Only '=' operator can be used for specifying default value.")
+      node.type = "AssignmentPattern"
+      delete node.operator
+      this.toAssignable(node.left, isBinding)
+      // falls through to AssignmentPattern
+
+    case "AssignmentPattern":
+      break
+
+    case "ParenthesizedExpression":
+      this.toAssignable(node.expression, isBinding)
+      break
+
+    case "MemberExpression":
+      if (!isBinding) break
+
+    default:
+      this.raise(node.start, "Assigning to rvalue")
+    }
+  } else if (refDestructuringErrors) this.checkPatternErrors(refDestructuringErrors, true)
+  return node
+}
+
+// Convert list of expression atoms to binding list.
+
+pp.toAssignableList = function(exprList, isBinding) {
+  let end = exprList.length
+  for (let i = 0; i < end; i++) {
+    let elt = exprList[i]
+    if (elt) this.toAssignable(elt, isBinding)
+  }
+  if (end) {
+    let last = exprList[end - 1]
+    if (this.options.ecmaVersion === 6 && isBinding && last && last.type === "RestElement" && last.argument.type !== "Identifier")
+      this.unexpected(last.argument.start)
+  }
+  return exprList
+}
+
+// Parses spread element.
+
+pp.parseSpread = function(refDestructuringErrors) {
+  let node = this.startNode()
+  this.next()
+  node.argument = this.parseMaybeAssign(false, refDestructuringErrors)
+  return this.finishNode(node, "SpreadElement")
+}
+
+pp.parseRestBinding = function() {
+  let node = this.startNode()
+  this.next()
+
+  // RestElement inside of a function parameter must be an identifier
+  if (this.options.ecmaVersion === 6 && this.type !== tt.name)
+    this.unexpected()
+
+  node.argument = this.parseBindingAtom()
+
+  return this.finishNode(node, "RestElement")
+}
+
+// Parses lvalue (assignable) atom.
+
+pp.parseBindingAtom = function() {
+  if (this.options.ecmaVersion >= 6) {
+    switch (this.type) {
+    case tt.bracketL:
+      let node = this.startNode()
+      this.next()
+      node.elements = this.parseBindingList(tt.bracketR, true, true)
+      return this.finishNode(node, "ArrayPattern")
+
+    case tt.braceL:
+      return this.parseObj(true)
+    }
+  }
+  return this.parseIdent()
+}
+
+pp.parseBindingList = function(close, allowEmpty, allowTrailingComma) {
+  let elts = [], first = true
+  while (!this.eat(close)) {
+    if (first) first = false
+    else this.expect(tt.comma)
+    if (allowEmpty && this.type === tt.comma) {
+      elts.push(null)
+    } else if (allowTrailingComma && this.afterTrailingComma(close)) {
+      break
+    } else if (this.type === tt.ellipsis) {
+      let rest = this.parseRestBinding()
+      this.parseBindingListItem(rest)
+      elts.push(rest)
+      if (this.type === tt.comma) this.raise(this.start, "Comma is not permitted after the rest element")
+      this.expect(close)
+      break
+    } else {
+      let elem = this.parseMaybeDefault(this.start, this.startLoc)
+      this.parseBindingListItem(elem)
+      elts.push(elem)
+    }
+  }
+  return elts
+}
+
+pp.parseBindingListItem = function(param) {
+  return param
+}
+
+// Parses assignment pattern around given atom if possible.
+
+pp.parseMaybeDefault = function(startPos, startLoc, left) {
+  left = left || this.parseBindingAtom()
+  if (this.options.ecmaVersion < 6 || !this.eat(tt.eq)) return left
+  let node = this.startNodeAt(startPos, startLoc)
+  node.left = left
+  node.right = this.parseMaybeAssign()
+  return this.finishNode(node, "AssignmentPattern")
+}
+
+// Verify that a node is an lval — something that can be assigned
+// to.
+// bindingType can be either:
+// 'var' indicating that the lval creates a 'var' binding
+// 'let' indicating that the lval creates a lexical ('let' or 'const') binding
+// 'none' indicating that the binding should be checked for illegal identifiers, but not for duplicate references
+
+pp.checkLVal = function(expr, bindingType, checkClashes) {
+  switch (expr.type) {
+  case "Identifier":
+    if (this.strict && this.reservedWordsStrictBind.test(expr.name))
+      this.raiseRecoverable(expr.start, (bindingType ? "Binding " : "Assigning to ") + expr.name + " in strict mode")
+    if (checkClashes) {
+      if (has(checkClashes, expr.name))
+        this.raiseRecoverable(expr.start, "Argument name clash")
+      checkClashes[expr.name] = true
+    }
+    if (bindingType && bindingType !== "none") {
+      if (
+        bindingType === "var" && !this.canDeclareVarName(expr.name) ||
+        bindingType !== "var" && !this.canDeclareLexicalName(expr.name)
+      ) {
+        this.raiseRecoverable(expr.start, `Identifier '${expr.name}' has already been declared`)
+      }
+      if (bindingType === "var") {
+        this.declareVarName(expr.name)
+      } else {
+        this.declareLexicalName(expr.name)
+      }
+    }
+    break
+
+  case "MemberExpression":
+    if (bindingType) this.raiseRecoverable(expr.start, "Binding member expression")
+    break
+
+  case "ObjectPattern":
+    for (let prop of expr.properties)
+      this.checkLVal(prop, bindingType, checkClashes)
+    break
+
+  case "Property":
+    // AssignmentProperty has type == "Property"
+    this.checkLVal(expr.value, bindingType, checkClashes)
+    break
+
+  case "ArrayPattern":
+    for (let elem of expr.elements) {
+      if (elem) this.checkLVal(elem, bindingType, checkClashes)
+    }
+    break
+
+  case "AssignmentPattern":
+    this.checkLVal(expr.left, bindingType, checkClashes)
+    break
+
+  case "RestElement":
+    this.checkLVal(expr.argument, bindingType, checkClashes)
+    break
+
+  case "ParenthesizedExpression":
+    this.checkLVal(expr.expression, bindingType, checkClashes)
+    break
+
+  default:
+    this.raise(expr.start, (bindingType ? "Binding" : "Assigning to") + " rvalue")
+  }
+}
diff --git a/tools/tests/apps/modules/imports/links/acorn/src/node.js b/tools/tests/apps/modules/imports/links/acorn/src/node.js
new file mode 100644
index 0000000000..76b5b09825
--- /dev/null
+++ b/tools/tests/apps/modules/imports/links/acorn/src/node.js
@@ -0,0 +1,50 @@
+import {Parser} from "./state"
+import {SourceLocation} from "./locutil"
+
+export class Node {
+  constructor(parser, pos, loc) {
+    this.type = ""
+    this.start = pos
+    this.end = 0
+    if (parser.options.locations)
+      this.loc = new SourceLocation(parser, loc)
+    if (parser.options.directSourceFile)
+      this.sourceFile = parser.options.directSourceFile
+    if (parser.options.ranges)
+      this.range = [pos, 0]
+  }
+}
+
+// Start an AST node, attaching a start offset.
+
+const pp = Parser.prototype
+
+pp.startNode = function() {
+  return new Node(this, this.start, this.startLoc)
+}
+
+pp.startNodeAt = function(pos, loc) {
+  return new Node(this, pos, loc)
+}
+
+// Finish an AST node, adding `type` and `end` properties.
+
+function finishNodeAt(node, type, pos, loc) {
+  node.type = type
+  node.end = pos
+  if (this.options.locations)
+    node.loc.end = loc
+  if (this.options.ranges)
+    node.range[1] = pos
+  return node
+}
+
+pp.finishNode = function(node, type) {
+  return finishNodeAt.call(this, node, type, this.lastTokEnd, this.lastTokEndLoc)
+}
+
+// Finish node at given position
+
+pp.finishNodeAt = function(node, type, pos, loc) {
+  return finishNodeAt.call(this, node, type, pos, loc)
+}
diff --git a/tools/tests/apps/modules/imports/links/acorn/src/options.js b/tools/tests/apps/modules/imports/links/acorn/src/options.js
new file mode 100644
index 0000000000..9dda44ae88
--- /dev/null
+++ b/tools/tests/apps/modules/imports/links/acorn/src/options.js
@@ -0,0 +1,127 @@
+import {has, isArray} from "./util"
+import {SourceLocation} from "./locutil"
+
+// A second optional argument can be given to further configure
+// the parser process. These options are recognized:
+
+export const defaultOptions = {
+  // `ecmaVersion` indicates the ECMAScript version to parse. Must
+  // be either 3, 5, 6 (2015), 7 (2016), or 8 (2017). This influences support
+  // for strict mode, the set of reserved words, and support for
+  // new syntax features. The default is 7.
+  ecmaVersion: 7,
+  // `sourceType` indicates the mode the code should be parsed in.
+  // Can be either `"script"` or `"module"`. This influences global
+  // strict mode and parsing of `import` and `export` declarations.
+  sourceType: "script",
+  // `onInsertedSemicolon` can be a callback that will be called
+  // when a semicolon is automatically inserted. It will be passed
+  // th position of the comma as an offset, and if `locations` is
+  // enabled, it is given the location as a `{line, column}` object
+  // as second argument.
+  onInsertedSemicolon: null,
+  // `onTrailingComma` is similar to `onInsertedSemicolon`, but for
+  // trailing commas.
+  onTrailingComma: null,
+  // By default, reserved words are only enforced if ecmaVersion >= 5.
+  // Set `allowReserved` to a boolean value to explicitly turn this on
+  // an off. When this option has the value "never", reserved words
+  // and keywords can also not be used as property names.
+  allowReserved: null,
+  // When enabled, a return at the top level is not considered an
+  // error.
+  allowReturnOutsideFunction: false,
+  // When enabled, import/export statements are not constrained to
+  // appearing at the top of the program.
+  allowImportExportEverywhere: false,
+  // When enabled, hashbang directive in the beginning of file
+  // is allowed and treated as a line comment.
+  allowHashBang: false,
+  // When `locations` is on, `loc` properties holding objects with
+  // `start` and `end` properties in `{line, column}` form (with
+  // line being 1-based and column 0-based) will be attached to the
+  // nodes.
+  locations: false,
+  // A function can be passed as `onToken` option, which will
+  // cause Acorn to call that function with object in the same
+  // format as tokens returned from `tokenizer().getToken()`. Note
+  // that you are not allowed to call the parser from the
+  // callback—that will corrupt its internal state.
+  onToken: null,
+  // A function can be passed as `onComment` option, which will
+  // cause Acorn to call that function with `(block, text, start,
+  // end)` parameters whenever a comment is skipped. `block` is a
+  // boolean indicating whether this is a block (`/* */`) comment,
+  // `text` is the content of the comment, and `start` and `end` are
+  // character offsets that denote the start and end of the comment.
+  // When the `locations` option is on, two more parameters are
+  // passed, the full `{line, column}` locations of the start and
+  // end of the comments. Note that you are not allowed to call the
+  // parser from the callback—that will corrupt its internal state.
+  onComment: null,
+  // Nodes have their start and end characters offsets recorded in
+  // `start` and `end` properties (directly on the node, rather than
+  // the `loc` object, which holds line/column data. To also add a
+  // [semi-standardized][range] `range` property holding a `[start,
+  // end]` array with the same numbers, set the `ranges` option to
+  // `true`.
+  //
+  // [range]: https://bugzilla.mozilla.org/show_bug.cgi?id=745678
+  ranges: false,
+  // It is possible to parse multiple files into a single AST by
+  // passing the tree produced by parsing the first file as
+  // `program` option in subsequent parses. This will add the
+  // toplevel forms of the parsed file to the `Program` (top) node
+  // of an existing parse tree.
+  program: null,
+  // When `locations` is on, you can pass this to record the source
+  // file in every node's `loc` object.
+  sourceFile: null,
+  // This value, if given, is stored in every node, whether
+  // `locations` is on or off.
+  directSourceFile: null,
+  // When enabled, parenthesized expressions are represented by
+  // (non-standard) ParenthesizedExpression nodes
+  preserveParens: false,
+  plugins: {}
+}
+
+// Interpret and default an options object
+
+export function getOptions(opts) {
+  let options = {}
+
+  for (let opt in defaultOptions)
+    options[opt] = opts && has(opts, opt) ? opts[opt] : defaultOptions[opt]
+
+  if (options.ecmaVersion >= 2015)
+    options.ecmaVersion -= 2009
+
+  if (options.allowReserved == null)
+    options.allowReserved = options.ecmaVersion < 5
+
+  if (isArray(options.onToken)) {
+    let tokens = options.onToken
+    options.onToken = (token) => tokens.push(token)
+  }
+  if (isArray(options.onComment))
+    options.onComment = pushComment(options, options.onComment)
+
+  return options
+}
+
+function pushComment(options, array) {
+  return function(block, text, start, end, startLoc, endLoc) {
+    let comment = {
+      type: block ? "Block" : "Line",
+      value: text,
+      start: start,
+      end: end
+    }
+    if (options.locations)
+      comment.loc = new SourceLocation(this, startLoc, endLoc)
+    if (options.ranges)
+      comment.range = [start, end]
+    array.push(comment)
+  }
+}
diff --git a/tools/tests/apps/modules/imports/links/acorn/src/parseutil.js b/tools/tests/apps/modules/imports/links/acorn/src/parseutil.js
new file mode 100644
index 0000000000..e1736372e5
--- /dev/null
+++ b/tools/tests/apps/modules/imports/links/acorn/src/parseutil.js
@@ -0,0 +1,137 @@
+import {types as tt} from "./tokentype"
+import {Parser} from "./state"
+import {lineBreak, skipWhiteSpace} from "./whitespace"
+
+const pp = Parser.prototype
+
+// ## Parser utilities
+
+const literal = /^(?:'((?:\\.|[^'])*?)'|"((?:\\.|[^"])*?)"|;)/
+pp.strictDirective = function(start) {
+  for (;;) {
+    skipWhiteSpace.lastIndex = start
+    start += skipWhiteSpace.exec(this.input)[0].length
+    let match = literal.exec(this.input.slice(start))
+    if (!match) return false
+    if ((match[1] || match[2]) == "use strict") return true
+    start += match[0].length
+  }
+}
+
+// Predicate that tests whether the next token is of the given
+// type, and if yes, consumes it as a side effect.
+
+pp.eat = function(type) {
+  if (this.type === type) {
+    this.next()
+    return true
+  } else {
+    return false
+  }
+}
+
+// Tests whether parsed token is a contextual keyword.
+
+pp.isContextual = function(name) {
+  return this.type === tt.name && this.value === name && !this.containsEsc
+}
+
+// Consumes contextual keyword if possible.
+
+pp.eatContextual = function(name) {
+  if (!this.isContextual(name)) return false
+  this.next()
+  return true
+}
+
+// Asserts that following token is given contextual keyword.
+
+pp.expectContextual = function(name) {
+  if (!this.eatContextual(name)) this.unexpected()
+}
+
+// Test whether a semicolon can be inserted at the current position.
+
+pp.canInsertSemicolon = function() {
+  return this.type === tt.eof ||
+    this.type === tt.braceR ||
+    lineBreak.test(this.input.slice(this.lastTokEnd, this.start))
+}
+
+pp.insertSemicolon = function() {
+  if (this.canInsertSemicolon()) {
+    if (this.options.onInsertedSemicolon)
+      this.options.onInsertedSemicolon(this.lastTokEnd, this.lastTokEndLoc)
+    return true
+  }
+}
+
+// Consume a semicolon, or, failing that, see if we are allowed to
+// pretend that there is a semicolon at this position.
+
+pp.semicolon = function() {
+  if (!this.eat(tt.semi) && !this.insertSemicolon()) this.unexpected()
+}
+
+pp.afterTrailingComma = function(tokType, notNext) {
+  if (this.type == tokType) {
+    if (this.options.onTrailingComma)
+      this.options.onTrailingComma(this.lastTokStart, this.lastTokStartLoc)
+    if (!notNext)
+      this.next()
+    return true
+  }
+}
+
+// Expect a token of a given type. If found, consume it, otherwise,
+// raise an unexpected token error.
+
+pp.expect = function(type) {
+  this.eat(type) || this.unexpected()
+}
+
+// Raise an unexpected token error.
+
+pp.unexpected = function(pos) {
+  this.raise(pos != null ? pos : this.start, "Unexpected token")
+}
+
+export function DestructuringErrors() {
+  this.shorthandAssign =
+  this.trailingComma =
+  this.parenthesizedAssign =
+  this.parenthesizedBind =
+  this.doubleProto =
+    -1
+}
+
+pp.checkPatternErrors = function(refDestructuringErrors, isAssign) {
+  if (!refDestructuringErrors) return
+  if (refDestructuringErrors.trailingComma > -1)
+    this.raiseRecoverable(refDestructuringErrors.trailingComma, "Comma is not permitted after the rest element")
+  let parens = isAssign ? refDestructuringErrors.parenthesizedAssign : refDestructuringErrors.parenthesizedBind
+  if (parens > -1) this.raiseRecoverable(parens, "Parenthesized pattern")
+}
+
+pp.checkExpressionErrors = function(refDestructuringErrors, andThrow) {
+  if (!refDestructuringErrors) return false
+  let {shorthandAssign, doubleProto} = refDestructuringErrors
+  if (!andThrow) return shorthandAssign >= 0 || doubleProto >= 0
+  if (shorthandAssign >= 0)
+    this.raise(shorthandAssign, "Shorthand property assignments are valid only in destructuring patterns")
+  if (doubleProto >= 0)
+    this.raiseRecoverable(doubleProto, "Redefinition of __proto__ property")
+}
+
+pp.checkYieldAwaitInDefaultParams = function() {
+  if (this.yieldPos && (!this.awaitPos || this.yieldPos < this.awaitPos))
+    this.raise(this.yieldPos, "Yield expression cannot be a default value")
+  if (this.awaitPos)
+    this.raise(this.awaitPos, "Await expression cannot be a default value")
+}
+
+pp.isSimpleAssignTarget = function(expr) {
+  if (expr.type === "ParenthesizedExpression")
+    return this.isSimpleAssignTarget(expr.expression)
+  return expr.type === "Identifier" || expr.type === "MemberExpression"
+}
diff --git a/tools/tests/apps/modules/imports/links/acorn/src/regexp.js b/tools/tests/apps/modules/imports/links/acorn/src/regexp.js
new file mode 100644
index 0000000000..c5953e3012
--- /dev/null
+++ b/tools/tests/apps/modules/imports/links/acorn/src/regexp.js
@@ -0,0 +1,1042 @@
+import {isIdentifierStart, isIdentifierChar} from "./identifier.js"
+import {Parser} from "./state.js"
+import UNICODE_PROPERTY_VALUES from "./unicode-property-data.js"
+
+const pp = Parser.prototype
+
+export class RegExpValidationState {
+  constructor(parser) {
+    this.parser = parser
+    this.validFlags = `gim${parser.options.ecmaVersion >= 6 ? "uy" : ""}${parser.options.ecmaVersion >= 9 ? "s" : ""}`
+    this.source = ""
+    this.flags = ""
+    this.start = 0
+    this.switchU = false
+    this.switchN = false
+    this.pos = 0
+    this.lastIntValue = 0
+    this.lastStringValue = ""
+    this.lastAssertionIsQuantifiable = false
+    this.numCapturingParens = 0
+    this.maxBackReference = 0
+    this.groupNames = []
+    this.backReferenceNames = []
+  }
+
+  reset(start, pattern, flags) {
+    const unicode = flags.indexOf("u") !== -1
+    this.start = start | 0
+    this.source = pattern + ""
+    this.flags = flags
+    this.switchU = unicode && this.parser.options.ecmaVersion >= 6
+    this.switchN = unicode && this.parser.options.ecmaVersion >= 9
+  }
+
+  raise(message) {
+    this.parser.raiseRecoverable(this.start, `Invalid regular expression: /${this.source}/: ${message}`)
+  }
+
+  // If u flag is given, this returns the code point at the index (it combines a surrogate pair).
+  // Otherwise, this returns the code unit of the index (can be a part of a surrogate pair).
+  at(i) {
+    const s = this.source
+    const l = s.length
+    if (i >= l) {
+      return -1
+    }
+    const c = s.charCodeAt(i)
+    if (!this.switchU || c <= 0xD7FF || c >= 0xE000 || i + 1 >= l) {
+      return c
+    }
+    return (c << 10) + s.charCodeAt(i + 1) - 0x35FDC00
+  }
+
+  nextIndex(i) {
+    const s = this.source
+    const l = s.length
+    if (i >= l) {
+      return l
+    }
+    const c = s.charCodeAt(i)
+    if (!this.switchU || c <= 0xD7FF || c >= 0xE000 || i + 1 >= l) {
+      return i + 1
+    }
+    return i + 2
+  }
+
+  current() {
+    return this.at(this.pos)
+  }
+
+  lookahead() {
+    return this.at(this.nextIndex(this.pos))
+  }
+
+  advance() {
+    this.pos = this.nextIndex(this.pos)
+  }
+
+  eat(ch) {
+    if (this.current() === ch) {
+      this.advance()
+      return true
+    }
+    return false
+  }
+}
+
+function codePointToString(ch) {
+  if (ch <= 0xFFFF) return String.fromCharCode(ch)
+  ch -= 0x10000
+  return String.fromCharCode((ch >> 10) + 0xD800, (ch & 0x03FF) + 0xDC00)
+}
+
+/**
+ * Validate the flags part of a given RegExpLiteral.
+ *
+ * @param {RegExpValidationState} state The state to validate RegExp.
+ * @returns {void}
+ */
+pp.validateRegExpFlags = function(state) {
+  const validFlags = state.validFlags
+  const flags = state.flags
+
+  for (let i = 0; i < flags.length; i++) {
+    const flag = flags.charAt(i)
+    if (validFlags.indexOf(flag) == -1) {
+      this.raise(state.start, "Invalid regular expression flag")
+    }
+    if (flags.indexOf(flag, i + 1) > -1) {
+      this.raise(state.start, "Duplicate regular expression flag")
+    }
+  }
+}
+
+/**
+ * Validate the pattern part of a given RegExpLiteral.
+ *
+ * @param {RegExpValidationState} state The state to validate RegExp.
+ * @returns {void}
+ */
+pp.validateRegExpPattern = function(state) {
+  this.regexp_pattern(state)
+
+  // The goal symbol for the parse is |Pattern[~U, ~N]|. If the result of
+  // parsing contains a |GroupName|, reparse with the goal symbol
+  // |Pattern[~U, +N]| and use this result instead. Throw a *SyntaxError*
+  // exception if _P_ did not conform to the grammar, if any elements of _P_
+  // were not matched by the parse, or if any Early Error conditions exist.
+  if (!state.switchN && this.options.ecmaVersion >= 9 && state.groupNames.length > 0) {
+    state.switchN = true
+    this.regexp_pattern(state)
+  }
+}
+
+// https://www.ecma-international.org/ecma-262/8.0/#prod-Pattern
+pp.regexp_pattern = function(state) {
+  state.pos = 0
+  state.lastIntValue = 0
+  state.lastStringValue = ""
+  state.lastAssertionIsQuantifiable = false
+  state.numCapturingParens = 0
+  state.maxBackReference = 0
+  state.groupNames.length = 0
+  state.backReferenceNames.length = 0
+
+  this.regexp_disjunction(state)
+
+  if (state.pos !== state.source.length) {
+    // Make the same messages as V8.
+    if (state.eat(0x29 /* ) */)) {
+      state.raise("Unmatched ')'")
+    }
+    if (state.eat(0x5D /* [ */) || state.eat(0x7D /* } */)) {
+      state.raise("Lone quantifier brackets")
+    }
+  }
+  if (state.maxBackReference > state.numCapturingParens) {
+    state.raise("Invalid escape")
+  }
+  for (const name of state.backReferenceNames) {
+    if (state.groupNames.indexOf(name) === -1) {
+      state.raise("Invalid named capture referenced")
+    }
+  }
+}
+
+// https://www.ecma-international.org/ecma-262/8.0/#prod-Disjunction
+pp.regexp_disjunction = function(state) {
+  this.regexp_alternative(state)
+  while (state.eat(0x7C /* | */)) {
+    this.regexp_alternative(state)
+  }
+
+  // Make the same message as V8.
+  if (this.regexp_eatQuantifier(state, true)) {
+    state.raise("Nothing to repeat")
+  }
+  if (state.eat(0x7B /* { */)) {
+    state.raise("Lone quantifier brackets")
+  }
+}
+
+// https://www.ecma-international.org/ecma-262/8.0/#prod-Alternative
+pp.regexp_alternative = function(state) {
+  while (state.pos < state.source.length && this.regexp_eatTerm(state))
+    ;
+}
+
+// https://www.ecma-international.org/ecma-262/8.0/#prod-annexB-Term
+pp.regexp_eatTerm = function(state) {
+  if (this.regexp_eatAssertion(state)) {
+    // Handle `QuantifiableAssertion Quantifier` alternative.
+    // `state.lastAssertionIsQuantifiable` is true if the last eaten Assertion
+    // is a QuantifiableAssertion.
+    if (state.lastAssertionIsQuantifiable && this.regexp_eatQuantifier(state)) {
+      // Make the same message as V8.
+      if (state.switchU) {
+        state.raise("Invalid quantifier")
+      }
+    }
+    return true
+  }
+
+  if (state.switchU ? this.regexp_eatAtom(state) : this.regexp_eatExtendedAtom(state)) {
+    this.regexp_eatQuantifier(state)
+    return true
+  }
+
+  return false
+}
+
+// https://www.ecma-international.org/ecma-262/8.0/#prod-annexB-Assertion
+pp.regexp_eatAssertion = function(state) {
+  const start = state.pos
+  state.lastAssertionIsQuantifiable = false
+
+  // ^, $
+  if (state.eat(0x5E /* ^ */) || state.eat(0x24 /* $ */)) {
+    return true
+  }
+
+  // \b \B
+  if (state.eat(0x5C /* \ */)) {
+    if (state.eat(0x42 /* B */) || state.eat(0x62 /* b */)) {
+      return true
+    }
+    state.pos = start
+  }
+
+  // Lookahead / Lookbehind
+  if (state.eat(0x28 /* ( */) && state.eat(0x3F /* ? */)) {
+    let lookbehind = false
+    if (this.options.ecmaVersion >= 9) {
+      lookbehind = state.eat(0x3C /* < */)
+    }
+    if (state.eat(0x3D /* = */) || state.eat(0x21 /* ! */)) {
+      this.regexp_disjunction(state)
+      if (!state.eat(0x29 /* ) */)) {
+        state.raise("Unterminated group")
+      }
+      state.lastAssertionIsQuantifiable = !lookbehind
+      return true
+    }
+  }
+
+  state.pos = start
+  return false
+}
+
+// https://www.ecma-international.org/ecma-262/8.0/#prod-Quantifier
+pp.regexp_eatQuantifier = function(state, noError = false) {
+  if (this.regexp_eatQuantifierPrefix(state, noError)) {
+    state.eat(0x3F /* ? */)
+    return true
+  }
+  return false
+}
+
+// https://www.ecma-international.org/ecma-262/8.0/#prod-QuantifierPrefix
+pp.regexp_eatQuantifierPrefix = function(state, noError) {
+  return (
+    state.eat(0x2A /* * */) ||
+    state.eat(0x2B /* + */) ||
+    state.eat(0x3F /* ? */) ||
+    this.regexp_eatBracedQuantifier(state, noError)
+  )
+}
+pp.regexp_eatBracedQuantifier = function(state, noError) {
+  const start = state.pos
+  if (state.eat(0x7B /* { */)) {
+    let min = 0, max = -1
+    if (this.regexp_eatDecimalDigits(state)) {
+      min = state.lastIntValue
+      if (state.eat(0x2C /* , */) && this.regexp_eatDecimalDigits(state)) {
+        max = state.lastIntValue
+      }
+      if (state.eat(0x7D /* } */)) {
+        // SyntaxError in https://www.ecma-international.org/ecma-262/8.0/#sec-term
+        if (max !== -1 && max < min && !noError) {
+          state.raise("numbers out of order in {} quantifier")
+        }
+        return true
+      }
+    }
+    if (state.switchU && !noError) {
+      state.raise("Incomplete quantifier")
+    }
+    state.pos = start
+  }
+  return false
+}
+
+// https://www.ecma-international.org/ecma-262/8.0/#prod-Atom
+pp.regexp_eatAtom = function(state) {
+  return (
+    this.regexp_eatPatternCharacters(state) ||
+    state.eat(0x2E /* . */) ||
+    this.regexp_eatReverseSolidusAtomEscape(state) ||
+    this.regexp_eatCharacterClass(state) ||
+    this.regexp_eatUncapturingGroup(state) ||
+    this.regexp_eatCapturingGroup(state)
+  )
+}
+pp.regexp_eatReverseSolidusAtomEscape = function(state) {
+  const start = state.pos
+  if (state.eat(0x5C /* \ */)) {
+    if (this.regexp_eatAtomEscape(state)) {
+      return true
+    }
+    state.pos = start
+  }
+  return false
+}
+pp.regexp_eatUncapturingGroup = function(state) {
+  const start = state.pos
+  if (state.eat(0x28 /* ( */)) {
+    if (state.eat(0x3F /* ? */) && state.eat(0x3A /* : */)) {
+      this.regexp_disjunction(state)
+      if (state.eat(0x29 /* ) */)) {
+        return true
+      }
+      state.raise("Unterminated group")
+    }
+    state.pos = start
+  }
+  return false
+}
+pp.regexp_eatCapturingGroup = function(state) {
+  if (state.eat(0x28 /* ( */)) {
+    if (this.options.ecmaVersion >= 9) {
+      this.regexp_groupSpecifier(state)
+    } else if (state.current() === 0x3F /* ? */) {
+      state.raise("Invalid group")
+    }
+    this.regexp_disjunction(state)
+    if (state.eat(0x29 /* ) */)) {
+      state.numCapturingParens += 1
+      return true
+    }
+    state.raise("Unterminated group")
+  }
+  return false
+}
+
+// https://www.ecma-international.org/ecma-262/8.0/#prod-annexB-ExtendedAtom
+pp.regexp_eatExtendedAtom = function(state) {
+  return (
+    state.eat(0x2E /* . */) ||
+    this.regexp_eatReverseSolidusAtomEscape(state) ||
+    this.regexp_eatCharacterClass(state) ||
+    this.regexp_eatUncapturingGroup(state) ||
+    this.regexp_eatCapturingGroup(state) ||
+    this.regexp_eatInvalidBracedQuantifier(state) ||
+    this.regexp_eatExtendedPatternCharacter(state)
+  )
+}
+
+// https://www.ecma-international.org/ecma-262/8.0/#prod-annexB-InvalidBracedQuantifier
+pp.regexp_eatInvalidBracedQuantifier = function(state) {
+  if (this.regexp_eatBracedQuantifier(state, true)) {
+    state.raise("Nothing to repeat")
+  }
+  return false
+}
+
+// https://www.ecma-international.org/ecma-262/8.0/#prod-SyntaxCharacter
+pp.regexp_eatSyntaxCharacter = function(state) {
+  const ch = state.current()
+  if (isSyntaxCharacter(ch)) {
+    state.lastIntValue = ch
+    state.advance()
+    return true
+  }
+  return false
+}
+function isSyntaxCharacter(ch) {
+  return (
+    ch === 0x24 /* $ */ ||
+    ch >= 0x28 /* ( */ && ch <= 0x2B /* + */ ||
+    ch === 0x2E /* . */ ||
+    ch === 0x3F /* ? */ ||
+    ch >= 0x5B /* [ */ && ch <= 0x5E /* ^ */ ||
+    ch >= 0x7B /* { */ && ch <= 0x7D /* } */
+  )
+}
+
+// https://www.ecma-international.org/ecma-262/8.0/#prod-PatternCharacter
+// But eat eager.
+pp.regexp_eatPatternCharacters = function(state) {
+  const start = state.pos
+  let ch = 0
+  while ((ch = state.current()) !== -1 && !isSyntaxCharacter(ch)) {
+    state.advance()
+  }
+  return state.pos !== start
+}
+
+// https://www.ecma-international.org/ecma-262/8.0/#prod-annexB-ExtendedPatternCharacter
+pp.regexp_eatExtendedPatternCharacter = function(state) {
+  const ch = state.current()
+  if (
+    ch !== -1 &&
+    ch !== 0x24 /* $ */ &&
+    !(ch >= 0x28 /* ( */ && ch <= 0x2B /* + */) &&
+    ch !== 0x2E /* . */ &&
+    ch !== 0x3F /* ? */ &&
+    ch !== 0x5B /* [ */ &&
+    ch !== 0x5E /* ^ */ &&
+    ch !== 0x7C /* | */
+  ) {
+    state.advance()
+    return true
+  }
+  return false
+}
+
+// GroupSpecifier[U] ::
+//   [empty]
+//   `?` GroupName[?U]
+pp.regexp_groupSpecifier = function(state) {
+  if (state.eat(0x3F /* ? */)) {
+    if (this.regexp_eatGroupName(state)) {
+      if (state.groupNames.indexOf(state.lastStringValue) !== -1) {
+        state.raise("Duplicate capture group name")
+      }
+      state.groupNames.push(state.lastStringValue)
+      return
+    }
+    state.raise("Invalid group")
+  }
+}
+
+// GroupName[U] ::
+//   `<` RegExpIdentifierName[?U] `>`
+// Note: this updates `state.lastStringValue` property with the eaten name.
+pp.regexp_eatGroupName = function(state) {
+  state.lastStringValue = ""
+  if (state.eat(0x3C /* < */)) {
+    if (this.regexp_eatRegExpIdentifierName(state) && state.eat(0x3E /* > */)) {
+      return true
+    }
+    state.raise("Invalid capture group name")
+  }
+  return false
+}
+
+// RegExpIdentifierName[U] ::
+//   RegExpIdentifierStart[?U]
+//   RegExpIdentifierName[?U] RegExpIdentifierPart[?U]
+// Note: this updates `state.lastStringValue` property with the eaten name.
+pp.regexp_eatRegExpIdentifierName = function(state) {
+  state.lastStringValue = ""
+  if (this.regexp_eatRegExpIdentifierStart(state)) {
+    state.lastStringValue += codePointToString(state.lastIntValue)
+    while (this.regexp_eatRegExpIdentifierPart(state)) {
+      state.lastStringValue += codePointToString(state.lastIntValue)
+    }
+    return true
+  }
+  return false
+}
+
+// RegExpIdentifierStart[U] ::
+//   UnicodeIDStart
+//   `$`
+//   `_`
+//   `\` RegExpUnicodeEscapeSequence[?U]
+pp.regexp_eatRegExpIdentifierStart = function(state) {
+  const start = state.pos
+  let ch = state.current()
+  state.advance()
+
+  if (ch === 0x5C /* \ */ && this.regexp_eatRegExpUnicodeEscapeSequence(state)) {
+    ch = state.lastIntValue
+  }
+  if (isRegExpIdentifierStart(ch)) {
+    state.lastIntValue = ch
+    return true
+  }
+
+  state.pos = start
+  return false
+}
+function isRegExpIdentifierStart(ch) {
+  return isIdentifierStart(ch, true) || ch === 0x24 /* $ */ || ch === 0x5F /* _ */
+}
+
+// RegExpIdentifierPart[U] ::
+//   UnicodeIDContinue
+//   `$`
+//   `_`
+//   `\` RegExpUnicodeEscapeSequence[?U]
+//   <ZWNJ>
+//   <ZWJ>
+pp.regexp_eatRegExpIdentifierPart = function(state) {
+  const start = state.pos
+  let ch = state.current()
+  state.advance()
+
+  if (ch === 0x5C /* \ */ && this.regexp_eatRegExpUnicodeEscapeSequence(state)) {
+    ch = state.lastIntValue
+  }
+  if (isRegExpIdentifierPart(ch)) {
+    state.lastIntValue = ch
+    return true
+  }
+
+  state.pos = start
+  return false
+}
+function isRegExpIdentifierPart(ch) {
+  return isIdentifierChar(ch, true) || ch === 0x24 /* $ */ || ch === 0x5F /* _ */ || ch === 0x200C /* <ZWNJ> */ || ch === 0x200D /* <ZWJ> */
+}
+
+// https://www.ecma-international.org/ecma-262/8.0/#prod-annexB-AtomEscape
+pp.regexp_eatAtomEscape = function(state) {
+  if (
+    this.regexp_eatBackReference(state) ||
+    this.regexp_eatCharacterClassEscape(state) ||
+    this.regexp_eatCharacterEscape(state) ||
+    (state.switchN && this.regexp_eatKGroupName(state))
+  ) {
+    return true
+  }
+  if (state.switchU) {
+    // Make the same message as V8.
+    if (state.current() === 0x63 /* c */) {
+      state.raise("Invalid unicode escape")
+    }
+    state.raise("Invalid escape")
+  }
+  return false
+}
+pp.regexp_eatBackReference = function(state) {
+  const start = state.pos
+  if (this.regexp_eatDecimalEscape(state)) {
+    const n = state.lastIntValue
+    if (state.switchU) {
+      // For SyntaxError in https://www.ecma-international.org/ecma-262/8.0/#sec-atomescape
+      if (n > state.maxBackReference) {
+        state.maxBackReference = n
+      }
+      return true
+    }
+    if (n <= state.numCapturingParens) {
+      return true
+    }
+    state.pos = start
+  }
+  return false
+}
+pp.regexp_eatKGroupName = function(state) {
+  if (state.eat(0x6B /* k */)) {
+    if (this.regexp_eatGroupName(state)) {
+      state.backReferenceNames.push(state.lastStringValue)
+      return true
+    }
+    state.raise("Invalid named reference")
+  }
+  return false
+}
+
+// https://www.ecma-international.org/ecma-262/8.0/#prod-annexB-CharacterEscape
+pp.regexp_eatCharacterEscape = function(state) {
+  return (
+    this.regexp_eatControlEscape(state) ||
+    this.regexp_eatCControlLetter(state) ||
+    this.regexp_eatZero(state) ||
+    this.regexp_eatHexEscapeSequence(state) ||
+    this.regexp_eatRegExpUnicodeEscapeSequence(state) ||
+    (!state.switchU && this.regexp_eatLegacyOctalEscapeSequence(state)) ||
+    this.regexp_eatIdentityEscape(state)
+  )
+}
+pp.regexp_eatCControlLetter = function(state) {
+  const start = state.pos
+  if (state.eat(0x63 /* c */)) {
+    if (this.regexp_eatControlLetter(state)) {
+      return true
+    }
+    state.pos = start
+  }
+  return false
+}
+pp.regexp_eatZero = function(state) {
+  if (state.current() === 0x30 /* 0 */ && !isDecimalDigit(state.lookahead())) {
+    state.lastIntValue = 0
+    state.advance()
+    return true
+  }
+  return false
+}
+
+// https://www.ecma-international.org/ecma-262/8.0/#prod-ControlEscape
+pp.regexp_eatControlEscape = function(state) {
+  const ch = state.current()
+  if (ch === 0x74 /* t */) {
+    state.lastIntValue = 0x09 /* \t */
+    state.advance()
+    return true
+  }
+  if (ch === 0x6E /* n */) {
+    state.lastIntValue = 0x0A /* \n */
+    state.advance()
+    return true
+  }
+  if (ch === 0x76 /* v */) {
+    state.lastIntValue = 0x0B /* \v */
+    state.advance()
+    return true
+  }
+  if (ch === 0x66 /* f */) {
+    state.lastIntValue = 0x0C /* \f */
+    state.advance()
+    return true
+  }
+  if (ch === 0x72 /* r */) {
+    state.lastIntValue = 0x0D /* \r */
+    state.advance()
+    return true
+  }
+  return false
+}
+
+// https://www.ecma-international.org/ecma-262/8.0/#prod-ControlLetter
+pp.regexp_eatControlLetter = function(state) {
+  const ch = state.current()
+  if (isControlLetter(ch)) {
+    state.lastIntValue = ch % 0x20
+    state.advance()
+    return true
+  }
+  return false
+}
+function isControlLetter(ch) {
+  return (
+    (ch >= 0x41 /* A */ && ch <= 0x5A /* Z */) ||
+    (ch >= 0x61 /* a */ && ch <= 0x7A /* z */)
+  )
+}
+
+// https://www.ecma-international.org/ecma-262/8.0/#prod-RegExpUnicodeEscapeSequence
+pp.regexp_eatRegExpUnicodeEscapeSequence = function(state) {
+  const start = state.pos
+
+  if (state.eat(0x75 /* u */)) {
+    if (this.regexp_eatFixedHexDigits(state, 4)) {
+      const lead = state.lastIntValue
+      if (state.switchU && lead >= 0xD800 && lead <= 0xDBFF) {
+        const leadSurrogateEnd = state.pos
+        if (state.eat(0x5C /* \ */) && state.eat(0x75 /* u */) && this.regexp_eatFixedHexDigits(state, 4)) {
+          const trail = state.lastIntValue
+          if (trail >= 0xDC00 && trail <= 0xDFFF) {
+            state.lastIntValue = (lead - 0xD800) * 0x400 + (trail - 0xDC00) + 0x10000
+            return true
+          }
+        }
+        state.pos = leadSurrogateEnd
+        state.lastIntValue = lead
+      }
+      return true
+    }
+    if (
+      state.switchU &&
+      state.eat(0x7B /* { */) &&
+      this.regexp_eatHexDigits(state) &&
+      state.eat(0x7D /* } */) &&
+      isValidUnicode(state.lastIntValue)
+    ) {
+      return true
+    }
+    if (state.switchU) {
+      state.raise("Invalid unicode escape")
+    }
+    state.pos = start
+  }
+
+  return false
+}
+function isValidUnicode(ch) {
+  return ch >= 0 && ch <= 0x10FFFF
+}
+
+// https://www.ecma-international.org/ecma-262/8.0/#prod-annexB-IdentityEscape
+pp.regexp_eatIdentityEscape = function(state) {
+  if (state.switchU) {
+    if (this.regexp_eatSyntaxCharacter(state)) {
+      return true
+    }
+    if (state.eat(0x2F /* / */)) {
+      state.lastIntValue = 0x2F /* / */
+      return true
+    }
+    return false
+  }
+
+  const ch = state.current()
+  if (ch !== 0x63 /* c */ && (!state.switchN || ch !== 0x6B /* k */)) {
+    state.lastIntValue = ch
+    state.advance()
+    return true
+  }
+
+  return false
+}
+
+// https://www.ecma-international.org/ecma-262/8.0/#prod-DecimalEscape
+pp.regexp_eatDecimalEscape = function(state) {
+  state.lastIntValue = 0
+  let ch = state.current()
+  if (ch >= 0x31 /* 1 */ && ch <= 0x39 /* 9 */) {
+    do {
+      state.lastIntValue = 10 * state.lastIntValue + (ch - 0x30 /* 0 */)
+      state.advance()
+    } while ((ch = state.current()) >= 0x30 /* 0 */ && ch <= 0x39 /* 9 */)
+    return true
+  }
+  return false
+}
+
+// https://www.ecma-international.org/ecma-262/8.0/#prod-CharacterClassEscape
+pp.regexp_eatCharacterClassEscape = function(state) {
+  const ch = state.current()
+
+  if (isCharacterClassEscape(ch)) {
+    state.lastIntValue = -1
+    state.advance()
+    return true
+  }
+
+  if (
+    state.switchU &&
+    this.options.ecmaVersion >= 9 &&
+    (ch === 0x50 /* P */ || ch === 0x70 /* p */)
+  ) {
+    state.lastIntValue = -1
+    state.advance()
+    if (
+      state.eat(0x7B /* { */) &&
+      this.regexp_eatUnicodePropertyValueExpression(state) &&
+      state.eat(0x7D /* } */)
+    ) {
+      return true
+    }
+    state.raise("Invalid property name")
+  }
+
+  return false
+}
+function isCharacterClassEscape(ch) {
+  return (
+    ch === 0x64 /* d */ ||
+    ch === 0x44 /* D */ ||
+    ch === 0x73 /* s */ ||
+    ch === 0x53 /* S */ ||
+    ch === 0x77 /* w */ ||
+    ch === 0x57 /* W */
+  )
+}
+
+// UnicodePropertyValueExpression ::
+//   UnicodePropertyName `=` UnicodePropertyValue
+//   LoneUnicodePropertyNameOrValue
+pp.regexp_eatUnicodePropertyValueExpression = function(state) {
+  const start = state.pos
+
+  // UnicodePropertyName `=` UnicodePropertyValue
+  if (this.regexp_eatUnicodePropertyName(state) && state.eat(0x3D /* = */)) {
+    const name = state.lastStringValue
+    if (this.regexp_eatUnicodePropertyValue(state)) {
+      const value = state.lastStringValue
+      this.regexp_validateUnicodePropertyNameAndValue(state, name, value)
+      return true
+    }
+  }
+  state.pos = start
+
+  // LoneUnicodePropertyNameOrValue
+  if (this.regexp_eatLoneUnicodePropertyNameOrValue(state)) {
+    const nameOrValue = state.lastStringValue
+    this.regexp_validateUnicodePropertyNameOrValue(state, nameOrValue)
+    return true
+  }
+  return false
+}
+pp.regexp_validateUnicodePropertyNameAndValue = function(state, name, value) {
+  if (!UNICODE_PROPERTY_VALUES.hasOwnProperty(name) || UNICODE_PROPERTY_VALUES[name].indexOf(value) === -1) {
+    state.raise("Invalid property name")
+  }
+}
+pp.regexp_validateUnicodePropertyNameOrValue = function(state, nameOrValue) {
+  if (UNICODE_PROPERTY_VALUES.$LONE.indexOf(nameOrValue) === -1) {
+    state.raise("Invalid property name")
+  }
+}
+
+// UnicodePropertyName ::
+//   UnicodePropertyNameCharacters
+pp.regexp_eatUnicodePropertyName = function(state) {
+  let ch = 0
+  state.lastStringValue = ""
+  while (isUnicodePropertyNameCharacter(ch = state.current())) {
+    state.lastStringValue += codePointToString(ch)
+    state.advance()
+  }
+  return state.lastStringValue !== ""
+}
+function isUnicodePropertyNameCharacter(ch) {
+  return isControlLetter(ch) || ch === 0x5F /* _ */
+}
+
+// UnicodePropertyValue ::
+//   UnicodePropertyValueCharacters
+pp.regexp_eatUnicodePropertyValue = function(state) {
+  let ch = 0
+  state.lastStringValue = ""
+  while (isUnicodePropertyValueCharacter(ch = state.current())) {
+    state.lastStringValue += codePointToString(ch)
+    state.advance()
+  }
+  return state.lastStringValue !== ""
+}
+function isUnicodePropertyValueCharacter(ch) {
+  return isUnicodePropertyNameCharacter(ch) || isDecimalDigit(ch)
+}
+
+// LoneUnicodePropertyNameOrValue ::
+//   UnicodePropertyValueCharacters
+pp.regexp_eatLoneUnicodePropertyNameOrValue = function(state) {
+  return this.regexp_eatUnicodePropertyValue(state)
+}
+
+// https://www.ecma-international.org/ecma-262/8.0/#prod-CharacterClass
+pp.regexp_eatCharacterClass = function(state) {
+  if (state.eat(0x5B /* [ */)) {
+    state.eat(0x5E /* ^ */)
+    this.regexp_classRanges(state)
+    if (state.eat(0x5D /* [ */)) {
+      return true
+    }
+    // Unreachable since it threw "unterminated regular expression" error before.
+    state.raise("Unterminated character class")
+  }
+  return false
+}
+
+// https://www.ecma-international.org/ecma-262/8.0/#prod-ClassRanges
+// https://www.ecma-international.org/ecma-262/8.0/#prod-NonemptyClassRanges
+// https://www.ecma-international.org/ecma-262/8.0/#prod-NonemptyClassRangesNoDash
+pp.regexp_classRanges = function(state) {
+  while (this.regexp_eatClassAtom(state)) {
+    const left = state.lastIntValue
+    if (state.eat(0x2D /* - */) && this.regexp_eatClassAtom(state)) {
+      const right = state.lastIntValue
+      if (state.switchU && (left === -1 || right === -1)) {
+        state.raise("Invalid character class")
+      }
+      if (left !== -1 && right !== -1 && left > right) {
+        state.raise("Range out of order in character class")
+      }
+    }
+  }
+}
+
+// https://www.ecma-international.org/ecma-262/8.0/#prod-ClassAtom
+// https://www.ecma-international.org/ecma-262/8.0/#prod-ClassAtomNoDash
+pp.regexp_eatClassAtom = function(state) {
+  const start = state.pos
+
+  if (state.eat(0x5C /* \ */)) {
+    if (this.regexp_eatClassEscape(state)) {
+      return true
+    }
+    if (state.switchU) {
+      // Make the same message as V8.
+      const ch = state.current()
+      if (ch === 0x63 /* c */ || isOctalDigit(ch)) {
+        state.raise("Invalid class escape")
+      }
+      state.raise("Invalid escape")
+    }
+    state.pos = start
+  }
+
+  const ch = state.current()
+  if (ch !== 0x5D /* [ */) {
+    state.lastIntValue = ch
+    state.advance()
+    return true
+  }
+
+  return false
+}
+
+// https://www.ecma-international.org/ecma-262/8.0/#prod-annexB-ClassEscape
+pp.regexp_eatClassEscape = function(state) {
+  const start = state.pos
+
+  if (state.eat(0x62 /* b */)) {
+    state.lastIntValue = 0x08 /* <BS> */
+    return true
+  }
+
+  if (state.switchU && state.eat(0x2D /* - */)) {
+    state.lastIntValue = 0x2D /* - */
+    return true
+  }
+
+  if (!state.switchU && state.eat(0x63 /* c */)) {
+    if (this.regexp_eatClassControlLetter(state)) {
+      return true
+    }
+    state.pos = start
+  }
+
+  return (
+    this.regexp_eatCharacterClassEscape(state) ||
+    this.regexp_eatCharacterEscape(state)
+  )
+}
+
+// https://www.ecma-international.org/ecma-262/8.0/#prod-annexB-ClassControlLetter
+pp.regexp_eatClassControlLetter = function(state) {
+  const ch = state.current()
+  if (isDecimalDigit(ch) || ch === 0x5F /* _ */) {
+    state.lastIntValue = ch % 0x20
+    state.advance()
+    return true
+  }
+  return false
+}
+
+// https://www.ecma-international.org/ecma-262/8.0/#prod-HexEscapeSequence
+pp.regexp_eatHexEscapeSequence = function(state) {
+  const start = state.pos
+  if (state.eat(0x78 /* x */)) {
+    if (this.regexp_eatFixedHexDigits(state, 2)) {
+      return true
+    }
+    if (state.switchU) {
+      state.raise("Invalid escape")
+    }
+    state.pos = start
+  }
+  return false
+}
+
+// https://www.ecma-international.org/ecma-262/8.0/#prod-DecimalDigits
+pp.regexp_eatDecimalDigits = function(state) {
+  const start = state.pos
+  let ch = 0
+  state.lastIntValue = 0
+  while (isDecimalDigit(ch = state.current())) {
+    state.lastIntValue = 10 * state.lastIntValue + (ch - 0x30 /* 0 */)
+    state.advance()
+  }
+  return state.pos !== start
+}
+function isDecimalDigit(ch) {
+  return ch >= 0x30 /* 0 */ && ch <= 0x39 /* 9 */
+}
+
+// https://www.ecma-international.org/ecma-262/8.0/#prod-HexDigits
+pp.regexp_eatHexDigits = function(state) {
+  const start = state.pos
+  let ch = 0
+  state.lastIntValue = 0
+  while (isHexDigit(ch = state.current())) {
+    state.lastIntValue = 16 * state.lastIntValue + hexToInt(ch)
+    state.advance()
+  }
+  return state.pos !== start
+}
+function isHexDigit(ch) {
+  return (
+    (ch >= 0x30 /* 0 */ && ch <= 0x39 /* 9 */) ||
+    (ch >= 0x41 /* A */ && ch <= 0x46 /* F */) ||
+    (ch >= 0x61 /* a */ && ch <= 0x66 /* f */)
+  )
+}
+function hexToInt(ch) {
+  if (ch >= 0x41 /* A */ && ch <= 0x46 /* F */) {
+    return 10 + (ch - 0x41 /* A */)
+  }
+  if (ch >= 0x61 /* a */ && ch <= 0x66 /* f */) {
+    return 10 + (ch - 0x61 /* a */)
+  }
+  return ch - 0x30 /* 0 */
+}
+
+// https://www.ecma-international.org/ecma-262/8.0/#prod-annexB-LegacyOctalEscapeSequence
+// Allows only 0-377(octal) i.e. 0-255(decimal).
+pp.regexp_eatLegacyOctalEscapeSequence = function(state) {
+  if (this.regexp_eatOctalDigit(state)) {
+    const n1 = state.lastIntValue
+    if (this.regexp_eatOctalDigit(state)) {
+      const n2 = state.lastIntValue
+      if (n1 <= 3 && this.regexp_eatOctalDigit(state)) {
+        state.lastIntValue = n1 * 64 + n2 * 8 + state.lastIntValue
+      } else {
+        state.lastIntValue = n1 * 8 + n2
+      }
+    } else {
+      state.lastIntValue = n1
+    }
+    return true
+  }
+  return false
+}
+
+// https://www.ecma-international.org/ecma-262/8.0/#prod-OctalDigit
+pp.regexp_eatOctalDigit = function(state) {
+  const ch = state.current()
+  if (isOctalDigit(ch)) {
+    state.lastIntValue = ch - 0x30 /* 0 */
+    state.advance()
+    return true
+  }
+  state.lastIntValue = 0
+  return false
+}
+function isOctalDigit(ch) {
+  return ch >= 0x30 /* 0 */ && ch <= 0x37 /* 7 */
+}
+
+// https://www.ecma-international.org/ecma-262/8.0/#prod-Hex4Digits
+// https://www.ecma-international.org/ecma-262/8.0/#prod-HexDigit
+// And HexDigit HexDigit in https://www.ecma-international.org/ecma-262/8.0/#prod-HexEscapeSequence
+pp.regexp_eatFixedHexDigits = function(state, length) {
+  const start = state.pos
+  state.lastIntValue = 0
+  for (let i = 0; i < length; ++i) {
+    const ch = state.current()
+    if (!isHexDigit(ch)) {
+      state.pos = start
+      return false
+    }
+    state.lastIntValue = 16 * state.lastIntValue + hexToInt(ch)
+    state.advance()
+  }
+  return true
+}
diff --git a/tools/tests/apps/modules/imports/links/acorn/src/scope.js b/tools/tests/apps/modules/imports/links/acorn/src/scope.js
new file mode 100644
index 0000000000..eab0002c04
--- /dev/null
+++ b/tools/tests/apps/modules/imports/links/acorn/src/scope.js
@@ -0,0 +1,74 @@
+import {Parser} from "./state"
+import {has} from "./util"
+
+const pp = Parser.prototype
+
+// Object.assign polyfill
+const assign = Object.assign || function(target, ...sources) {
+  for (let source of sources) {
+    for (const key in source) {
+      if (has(source, key)) {
+        target[key] = source[key]
+      }
+    }
+  }
+  return target
+}
+
+// The functions in this module keep track of declared variables in the current scope in order to detect duplicate variable names.
+
+pp.enterFunctionScope = function() {
+  // var: a hash of var-declared names in the current lexical scope
+  // lexical: a hash of lexically-declared names in the current lexical scope
+  // childVar: a hash of var-declared names in all child lexical scopes of the current lexical scope (within the current function scope)
+  // parentLexical: a hash of lexically-declared names in all parent lexical scopes of the current lexical scope (within the current function scope)
+  this.scopeStack.push({var: {}, lexical: {}, childVar: {}, parentLexical: {}})
+}
+
+pp.exitFunctionScope = function() {
+  this.scopeStack.pop()
+}
+
+pp.enterLexicalScope = function() {
+  const parentScope = this.scopeStack[this.scopeStack.length - 1]
+  const childScope = {var: {}, lexical: {}, childVar: {}, parentLexical: {}}
+
+  this.scopeStack.push(childScope)
+  assign(childScope.parentLexical, parentScope.lexical, parentScope.parentLexical)
+}
+
+pp.exitLexicalScope = function() {
+  const childScope = this.scopeStack.pop()
+  const parentScope = this.scopeStack[this.scopeStack.length - 1]
+
+  assign(parentScope.childVar, childScope.var, childScope.childVar)
+}
+
+/**
+ * A name can be declared with `var` if there are no variables with the same name declared with `let`/`const`
+ * in the current lexical scope or any of the parent lexical scopes in this function.
+ */
+pp.canDeclareVarName = function(name) {
+  const currentScope = this.scopeStack[this.scopeStack.length - 1]
+
+  return !has(currentScope.lexical, name) && !has(currentScope.parentLexical, name)
+}
+
+/**
+ * A name can be declared with `let`/`const` if there are no variables with the same name declared with `let`/`const`
+ * in the current scope, and there are no variables with the same name declared with `var` in the current scope or in
+ * any child lexical scopes in this function.
+ */
+pp.canDeclareLexicalName = function(name) {
+  const currentScope = this.scopeStack[this.scopeStack.length - 1]
+
+  return !has(currentScope.lexical, name) && !has(currentScope.var, name) && !has(currentScope.childVar, name)
+}
+
+pp.declareVarName = function(name) {
+  this.scopeStack[this.scopeStack.length - 1].var[name] = true
+}
+
+pp.declareLexicalName = function(name) {
+  this.scopeStack[this.scopeStack.length - 1].lexical[name] = true
+}
diff --git a/tools/tests/apps/modules/imports/links/acorn/src/state.js b/tools/tests/apps/modules/imports/links/acorn/src/state.js
new file mode 100644
index 0000000000..185fe28648
--- /dev/null
+++ b/tools/tests/apps/modules/imports/links/acorn/src/state.js
@@ -0,0 +1,118 @@
+import {reservedWords, keywords} from "./identifier"
+import {types as tt} from "./tokentype"
+import {lineBreak} from "./whitespace"
+import {getOptions} from "./options"
+
+// Registered plugins
+export const plugins = {}
+
+function keywordRegexp(words) {
+  return new RegExp("^(?:" + words.replace(/ /g, "|") + ")$")
+}
+
+export class Parser {
+  constructor(options, input, startPos) {
+    this.options = options = getOptions(options)
+    this.sourceFile = options.sourceFile
+    this.keywords = keywordRegexp(keywords[options.ecmaVersion >= 6 ? 6 : 5])
+    let reserved = ""
+    if (!options.allowReserved) {
+      for (let v = options.ecmaVersion;; v--)
+        if (reserved = reservedWords[v]) break
+      if (options.sourceType == "module") reserved += " await"
+    }
+    this.reservedWords = keywordRegexp(reserved)
+    let reservedStrict = (reserved ? reserved + " " : "") + reservedWords.strict
+    this.reservedWordsStrict = keywordRegexp(reservedStrict)
+    this.reservedWordsStrictBind = keywordRegexp(reservedStrict + " " + reservedWords.strictBind)
+    this.input = String(input)
+
+    // Used to signal to callers of `readWord1` whether the word
+    // contained any escape sequences. This is needed because words with
+    // escape sequences must not be interpreted as keywords.
+    this.containsEsc = false
+
+    // Load plugins
+    this.loadPlugins(options.plugins)
+
+    // Set up token state
+
+    // The current position of the tokenizer in the input.
+    if (startPos) {
+      this.pos = startPos
+      this.lineStart = this.input.lastIndexOf("\n", startPos - 1) + 1
+      this.curLine = this.input.slice(0, this.lineStart).split(lineBreak).length
+    } else {
+      this.pos = this.lineStart = 0
+      this.curLine = 1
+    }
+
+    // Properties of the current token:
+    // Its type
+    this.type = tt.eof
+    // For tokens that include more information than their type, the value
+    this.value = null
+    // Its start and end offset
+    this.start = this.end = this.pos
+    // And, if locations are used, the {line, column} object
+    // corresponding to those offsets
+    this.startLoc = this.endLoc = this.curPosition()
+
+    // Position information for the previous token
+    this.lastTokEndLoc = this.lastTokStartLoc = null
+    this.lastTokStart = this.lastTokEnd = this.pos
+
+    // The context stack is used to superficially track syntactic
+    // context to predict whether a regular expression is allowed in a
+    // given position.
+    this.context = this.initialContext()
+    this.exprAllowed = true
+
+    // Figure out if it's a module code.
+    this.inModule = options.sourceType === "module"
+    this.strict = this.inModule || this.strictDirective(this.pos)
+
+    // Used to signify the start of a potential arrow function
+    this.potentialArrowAt = -1
+
+    // Flags to track whether we are in a function, a generator, an async function.
+    this.inFunction = this.inGenerator = this.inAsync = false
+    // Positions to delayed-check that yield/await does not exist in default parameters.
+    this.yieldPos = this.awaitPos = 0
+    // Labels in scope.
+    this.labels = []
+
+    // If enabled, skip leading hashbang line.
+    if (this.pos === 0 && options.allowHashBang && this.input.slice(0, 2) === "#!")
+      this.skipLineComment(2)
+
+    // Scope tracking for duplicate variable names (see scope.js)
+    this.scopeStack = []
+    this.enterFunctionScope()
+
+    // For RegExp validation
+    this.regexpState = null
+  }
+
+  // DEPRECATED Kept for backwards compatibility until 3.0 in case a plugin uses them
+  isKeyword(word) { return this.keywords.test(word) }
+  isReservedWord(word) { return this.reservedWords.test(word) }
+
+  extend(name, f) {
+    this[name] = f(this[name])
+  }
+
+  loadPlugins(pluginConfigs) {
+    for (let name in pluginConfigs) {
+      let plugin = plugins[name]
+      if (!plugin) throw new Error("Plugin '" + name + "' not found")
+      plugin(this, pluginConfigs[name])
+    }
+  }
+
+  parse() {
+    let node = this.options.program || this.startNode()
+    this.nextToken()
+    return this.parseTopLevel(node)
+  }
+}
diff --git a/tools/tests/apps/modules/imports/links/acorn/src/statement.js b/tools/tests/apps/modules/imports/links/acorn/src/statement.js
new file mode 100644
index 0000000000..2612125df3
--- /dev/null
+++ b/tools/tests/apps/modules/imports/links/acorn/src/statement.js
@@ -0,0 +1,810 @@
+import {types as tt} from "./tokentype"
+import {Parser} from "./state"
+import {lineBreak, skipWhiteSpace} from "./whitespace"
+import {isIdentifierStart, isIdentifierChar, keywordRelationalOperator} from "./identifier"
+import {has} from "./util"
+import {DestructuringErrors} from "./parseutil"
+
+const pp = Parser.prototype
+
+// ### Statement parsing
+
+// Parse a program. Initializes the parser, reads any number of
+// statements, and wraps them in a Program node.  Optionally takes a
+// `program` argument.  If present, the statements will be appended
+// to its body instead of creating a new node.
+
+pp.parseTopLevel = function(node) {
+  let exports = {}
+  if (!node.body) node.body = []
+  while (this.type !== tt.eof) {
+    let stmt = this.parseStatement(true, true, exports)
+    node.body.push(stmt)
+  }
+  this.adaptDirectivePrologue(node.body)
+  this.next()
+  if (this.options.ecmaVersion >= 6) {
+    node.sourceType = this.options.sourceType
+  }
+  return this.finishNode(node, "Program")
+}
+
+const loopLabel = {kind: "loop"}, switchLabel = {kind: "switch"}
+
+pp.isLet = function() {
+  if (this.options.ecmaVersion < 6 || !this.isContextual("let")) return false
+  skipWhiteSpace.lastIndex = this.pos
+  let skip = skipWhiteSpace.exec(this.input)
+  let next = this.pos + skip[0].length, nextCh = this.input.charCodeAt(next)
+  if (nextCh === 91 || nextCh == 123) return true // '{' and '['
+  if (isIdentifierStart(nextCh, true)) {
+    let pos = next + 1
+    while (isIdentifierChar(this.input.charCodeAt(pos), true)) ++pos
+    let ident = this.input.slice(next, pos)
+    if (!keywordRelationalOperator.test(ident)) return true
+  }
+  return false
+}
+
+// check 'async [no LineTerminator here] function'
+// - 'async /*foo*/ function' is OK.
+// - 'async /*\n*/ function' is invalid.
+pp.isAsyncFunction = function() {
+  if (this.options.ecmaVersion < 8 || !this.isContextual("async"))
+    return false
+
+  skipWhiteSpace.lastIndex = this.pos
+  let skip = skipWhiteSpace.exec(this.input)
+  let next = this.pos + skip[0].length
+  return !lineBreak.test(this.input.slice(this.pos, next)) &&
+    this.input.slice(next, next + 8) === "function" &&
+    (next + 8 == this.input.length || !isIdentifierChar(this.input.charAt(next + 8)))
+}
+
+// Parse a single statement.
+//
+// If expecting a statement and finding a slash operator, parse a
+// regular expression literal. This is to handle cases like
+// `if (foo) /blah/.exec(foo)`, where looking at the previous token
+// does not help.
+
+pp.parseStatement = function(declaration, topLevel, exports) {
+  let starttype = this.type, node = this.startNode(), kind
+
+  if (this.isLet()) {
+    starttype = tt._var
+    kind = "let"
+  }
+
+  // Most types of statements are recognized by the keyword they
+  // start with. Many are trivial to parse, some require a bit of
+  // complexity.
+
+  switch (starttype) {
+  case tt._break: case tt._continue: return this.parseBreakContinueStatement(node, starttype.keyword)
+  case tt._debugger: return this.parseDebuggerStatement(node)
+  case tt._do: return this.parseDoStatement(node)
+  case tt._for: return this.parseForStatement(node)
+  case tt._function:
+    if (!declaration && this.options.ecmaVersion >= 6) this.unexpected()
+    return this.parseFunctionStatement(node, false)
+  case tt._class:
+    if (!declaration) this.unexpected()
+    return this.parseClass(node, true)
+  case tt._if: return this.parseIfStatement(node)
+  case tt._return: return this.parseReturnStatement(node)
+  case tt._switch: return this.parseSwitchStatement(node)
+  case tt._throw: return this.parseThrowStatement(node)
+  case tt._try: return this.parseTryStatement(node)
+  case tt._const: case tt._var:
+    kind = kind || this.value
+    if (!declaration && kind != "var") this.unexpected()
+    return this.parseVarStatement(node, kind)
+  case tt._while: return this.parseWhileStatement(node)
+  case tt._with: return this.parseWithStatement(node)
+  case tt.braceL: return this.parseBlock()
+  case tt.semi: return this.parseEmptyStatement(node)
+  case tt._export:
+  case tt._import:
+    if (!this.options.allowImportExportEverywhere) {
+      if (!topLevel)
+        this.raise(this.start, "'import' and 'export' may only appear at the top level")
+      if (!this.inModule)
+        this.raise(this.start, "'import' and 'export' may appear only with 'sourceType: module'")
+    }
+    return starttype === tt._import ? this.parseImport(node) : this.parseExport(node, exports)
+
+    // If the statement does not start with a statement keyword or a
+    // brace, it's an ExpressionStatement or LabeledStatement. We
+    // simply start parsing an expression, and afterwards, if the
+    // next token is a colon and the expression was a simple
+    // Identifier node, we switch to interpreting it as a label.
+  default:
+    if (this.isAsyncFunction()) {
+      if (!declaration) this.unexpected()
+      this.next()
+      return this.parseFunctionStatement(node, true)
+    }
+
+    let maybeName = this.value, expr = this.parseExpression()
+    if (starttype === tt.name && expr.type === "Identifier" && this.eat(tt.colon))
+      return this.parseLabeledStatement(node, maybeName, expr)
+    else return this.parseExpressionStatement(node, expr)
+  }
+}
+
+pp.parseBreakContinueStatement = function(node, keyword) {
+  let isBreak = keyword == "break"
+  this.next()
+  if (this.eat(tt.semi) || this.insertSemicolon()) node.label = null
+  else if (this.type !== tt.name) this.unexpected()
+  else {
+    node.label = this.parseIdent()
+    this.semicolon()
+  }
+
+  // Verify that there is an actual destination to break or
+  // continue to.
+  let i = 0
+  for (; i < this.labels.length; ++i) {
+    let lab = this.labels[i]
+    if (node.label == null || lab.name === node.label.name) {
+      if (lab.kind != null && (isBreak || lab.kind === "loop")) break
+      if (node.label && isBreak) break
+    }
+  }
+  if (i === this.labels.length) this.raise(node.start, "Unsyntactic " + keyword)
+  return this.finishNode(node, isBreak ? "BreakStatement" : "ContinueStatement")
+}
+
+pp.parseDebuggerStatement = function(node) {
+  this.next()
+  this.semicolon()
+  return this.finishNode(node, "DebuggerStatement")
+}
+
+pp.parseDoStatement = function(node) {
+  this.next()
+  this.labels.push(loopLabel)
+  node.body = this.parseStatement(false)
+  this.labels.pop()
+  this.expect(tt._while)
+  node.test = this.parseParenExpression()
+  if (this.options.ecmaVersion >= 6)
+    this.eat(tt.semi)
+  else
+    this.semicolon()
+  return this.finishNode(node, "DoWhileStatement")
+}
+
+// Disambiguating between a `for` and a `for`/`in` or `for`/`of`
+// loop is non-trivial. Basically, we have to parse the init `var`
+// statement or expression, disallowing the `in` operator (see
+// the second parameter to `parseExpression`), and then check
+// whether the next token is `in` or `of`. When there is no init
+// part (semicolon immediately after the opening parenthesis), it
+// is a regular `for` loop.
+
+pp.parseForStatement = function(node) {
+  this.next()
+  let awaitAt = (this.options.ecmaVersion >= 9 && this.inAsync && this.eatContextual("await")) ? this.lastTokStart : -1
+  this.labels.push(loopLabel)
+  this.enterLexicalScope()
+  this.expect(tt.parenL)
+  if (this.type === tt.semi) {
+    if (awaitAt > -1) this.unexpected(awaitAt)
+    return this.parseFor(node, null)
+  }
+  let isLet = this.isLet()
+  if (this.type === tt._var || this.type === tt._const || isLet) {
+    let init = this.startNode(), kind = isLet ? "let" : this.value
+    this.next()
+    this.parseVar(init, true, kind)
+    this.finishNode(init, "VariableDeclaration")
+    if ((this.type === tt._in || (this.options.ecmaVersion >= 6 && this.isContextual("of"))) && init.declarations.length === 1 &&
+        !(kind !== "var" && init.declarations[0].init)) {
+      if (this.options.ecmaVersion >= 9) {
+        if (this.type === tt._in) {
+          if (awaitAt > -1) this.unexpected(awaitAt)
+        } else node.await = awaitAt > -1
+      }
+      return this.parseForIn(node, init)
+    }
+    if (awaitAt > -1) this.unexpected(awaitAt)
+    return this.parseFor(node, init)
+  }
+  let refDestructuringErrors = new DestructuringErrors
+  let init = this.parseExpression(true, refDestructuringErrors)
+  if (this.type === tt._in || (this.options.ecmaVersion >= 6 && this.isContextual("of"))) {
+    if (this.options.ecmaVersion >= 9) {
+      if (this.type === tt._in) {
+        if (awaitAt > -1) this.unexpected(awaitAt)
+      } else node.await = awaitAt > -1
+    }
+    this.toAssignable(init, false, refDestructuringErrors)
+    this.checkLVal(init)
+    return this.parseForIn(node, init)
+  } else {
+    this.checkExpressionErrors(refDestructuringErrors, true)
+  }
+  if (awaitAt > -1) this.unexpected(awaitAt)
+  return this.parseFor(node, init)
+}
+
+pp.parseFunctionStatement = function(node, isAsync) {
+  this.next()
+  return this.parseFunction(node, true, false, isAsync)
+}
+
+pp.parseIfStatement = function(node) {
+  this.next()
+  node.test = this.parseParenExpression()
+  // allow function declarations in branches, but only in non-strict mode
+  node.consequent = this.parseStatement(!this.strict && this.type == tt._function)
+  node.alternate = this.eat(tt._else) ? this.parseStatement(!this.strict && this.type == tt._function) : null
+  return this.finishNode(node, "IfStatement")
+}
+
+pp.parseReturnStatement = function(node) {
+  if (!this.inFunction && !this.options.allowReturnOutsideFunction)
+    this.raise(this.start, "'return' outside of function")
+  this.next()
+
+  // In `return` (and `break`/`continue`), the keywords with
+  // optional arguments, we eagerly look for a semicolon or the
+  // possibility to insert one.
+
+  if (this.eat(tt.semi) || this.insertSemicolon()) node.argument = null
+  else { node.argument = this.parseExpression(); this.semicolon() }
+  return this.finishNode(node, "ReturnStatement")
+}
+
+pp.parseSwitchStatement = function(node) {
+  this.next()
+  node.discriminant = this.parseParenExpression()
+  node.cases = []
+  this.expect(tt.braceL)
+  this.labels.push(switchLabel)
+  this.enterLexicalScope()
+
+  // Statements under must be grouped (by label) in SwitchCase
+  // nodes. `cur` is used to keep the node that we are currently
+  // adding statements to.
+
+  let cur
+  for (let sawDefault = false; this.type != tt.braceR;) {
+    if (this.type === tt._case || this.type === tt._default) {
+      let isCase = this.type === tt._case
+      if (cur) this.finishNode(cur, "SwitchCase")
+      node.cases.push(cur = this.startNode())
+      cur.consequent = []
+      this.next()
+      if (isCase) {
+        cur.test = this.parseExpression()
+      } else {
+        if (sawDefault) this.raiseRecoverable(this.lastTokStart, "Multiple default clauses")
+        sawDefault = true
+        cur.test = null
+      }
+      this.expect(tt.colon)
+    } else {
+      if (!cur) this.unexpected()
+      cur.consequent.push(this.parseStatement(true))
+    }
+  }
+  this.exitLexicalScope()
+  if (cur) this.finishNode(cur, "SwitchCase")
+  this.next() // Closing brace
+  this.labels.pop()
+  return this.finishNode(node, "SwitchStatement")
+}
+
+pp.parseThrowStatement = function(node) {
+  this.next()
+  if (lineBreak.test(this.input.slice(this.lastTokEnd, this.start)))
+    this.raise(this.lastTokEnd, "Illegal newline after throw")
+  node.argument = this.parseExpression()
+  this.semicolon()
+  return this.finishNode(node, "ThrowStatement")
+}
+
+// Reused empty array added for node fields that are always empty.
+
+const empty = []
+
+pp.parseTryStatement = function(node) {
+  this.next()
+  node.block = this.parseBlock()
+  node.handler = null
+  if (this.type === tt._catch) {
+    let clause = this.startNode()
+    this.next()
+    this.expect(tt.parenL)
+    clause.param = this.parseBindingAtom()
+    this.enterLexicalScope()
+    this.checkLVal(clause.param, "let")
+    this.expect(tt.parenR)
+    clause.body = this.parseBlock(false)
+    this.exitLexicalScope()
+    node.handler = this.finishNode(clause, "CatchClause")
+  }
+  node.finalizer = this.eat(tt._finally) ? this.parseBlock() : null
+  if (!node.handler && !node.finalizer)
+    this.raise(node.start, "Missing catch or finally clause")
+  return this.finishNode(node, "TryStatement")
+}
+
+pp.parseVarStatement = function(node, kind) {
+  this.next()
+  this.parseVar(node, false, kind)
+  this.semicolon()
+  return this.finishNode(node, "VariableDeclaration")
+}
+
+pp.parseWhileStatement = function(node) {
+  this.next()
+  node.test = this.parseParenExpression()
+  this.labels.push(loopLabel)
+  node.body = this.parseStatement(false)
+  this.labels.pop()
+  return this.finishNode(node, "WhileStatement")
+}
+
+pp.parseWithStatement = function(node) {
+  if (this.strict) this.raise(this.start, "'with' in strict mode")
+  this.next()
+  node.object = this.parseParenExpression()
+  node.body = this.parseStatement(false)
+  return this.finishNode(node, "WithStatement")
+}
+
+pp.parseEmptyStatement = function(node) {
+  this.next()
+  return this.finishNode(node, "EmptyStatement")
+}
+
+pp.parseLabeledStatement = function(node, maybeName, expr) {
+  for (let label of this.labels)
+    if (label.name === maybeName)
+      this.raise(expr.start, "Label '" + maybeName + "' is already declared")
+  let kind = this.type.isLoop ? "loop" : this.type === tt._switch ? "switch" : null
+  for (let i = this.labels.length - 1; i >= 0; i--) {
+    let label = this.labels[i]
+    if (label.statementStart == node.start) {
+      // Update information about previous labels on this node
+      label.statementStart = this.start
+      label.kind = kind
+    } else break
+  }
+  this.labels.push({name: maybeName, kind, statementStart: this.start})
+  node.body = this.parseStatement(true)
+  if (node.body.type == "ClassDeclaration" ||
+      node.body.type == "VariableDeclaration" && node.body.kind != "var" ||
+      node.body.type == "FunctionDeclaration" && (this.strict || node.body.generator))
+    this.raiseRecoverable(node.body.start, "Invalid labeled declaration")
+  this.labels.pop()
+  node.label = expr
+  return this.finishNode(node, "LabeledStatement")
+}
+
+pp.parseExpressionStatement = function(node, expr) {
+  node.expression = expr
+  this.semicolon()
+  return this.finishNode(node, "ExpressionStatement")
+}
+
+// Parse a semicolon-enclosed block of statements, handling `"use
+// strict"` declarations when `allowStrict` is true (used for
+// function bodies).
+
+pp.parseBlock = function(createNewLexicalScope = true) {
+  let node = this.startNode()
+  node.body = []
+  this.expect(tt.braceL)
+  if (createNewLexicalScope) {
+    this.enterLexicalScope()
+  }
+  while (!this.eat(tt.braceR)) {
+    let stmt = this.parseStatement(true)
+    node.body.push(stmt)
+  }
+  if (createNewLexicalScope) {
+    this.exitLexicalScope()
+  }
+  return this.finishNode(node, "BlockStatement")
+}
+
+// Parse a regular `for` loop. The disambiguation code in
+// `parseStatement` will already have parsed the init statement or
+// expression.
+
+pp.parseFor = function(node, init) {
+  node.init = init
+  this.expect(tt.semi)
+  node.test = this.type === tt.semi ? null : this.parseExpression()
+  this.expect(tt.semi)
+  node.update = this.type === tt.parenR ? null : this.parseExpression()
+  this.expect(tt.parenR)
+  this.exitLexicalScope()
+  node.body = this.parseStatement(false)
+  this.labels.pop()
+  return this.finishNode(node, "ForStatement")
+}
+
+// Parse a `for`/`in` and `for`/`of` loop, which are almost
+// same from parser's perspective.
+
+pp.parseForIn = function(node, init) {
+  let type = this.type === tt._in ? "ForInStatement" : "ForOfStatement"
+  this.next()
+  if (type == "ForInStatement") {
+    if (init.type === "AssignmentPattern" ||
+      (init.type === "VariableDeclaration" && init.declarations[0].init != null &&
+       (this.strict || init.declarations[0].id.type !== "Identifier")))
+      this.raise(init.start, "Invalid assignment in for-in loop head")
+  }
+  node.left = init
+  node.right = type == "ForInStatement" ? this.parseExpression() : this.parseMaybeAssign()
+  this.expect(tt.parenR)
+  this.exitLexicalScope()
+  node.body = this.parseStatement(false)
+  this.labels.pop()
+  return this.finishNode(node, type)
+}
+
+// Parse a list of variable declarations.
+
+pp.parseVar = function(node, isFor, kind) {
+  node.declarations = []
+  node.kind = kind
+  for (;;) {
+    let decl = this.startNode()
+    this.parseVarId(decl, kind)
+    if (this.eat(tt.eq)) {
+      decl.init = this.parseMaybeAssign(isFor)
+    } else if (kind === "const" && !(this.type === tt._in || (this.options.ecmaVersion >= 6 && this.isContextual("of")))) {
+      this.unexpected()
+    } else if (decl.id.type != "Identifier" && !(isFor && (this.type === tt._in || this.isContextual("of")))) {
+      this.raise(this.lastTokEnd, "Complex binding patterns require an initialization value")
+    } else {
+      decl.init = null
+    }
+    node.declarations.push(this.finishNode(decl, "VariableDeclarator"))
+    if (!this.eat(tt.comma)) break
+  }
+  return node
+}
+
+pp.parseVarId = function(decl, kind) {
+  decl.id = this.parseBindingAtom(kind)
+  this.checkLVal(decl.id, kind, false)
+}
+
+// Parse a function declaration or literal (depending on the
+// `isStatement` parameter).
+
+pp.parseFunction = function(node, isStatement, allowExpressionBody, isAsync) {
+  this.initFunction(node)
+  if (this.options.ecmaVersion >= 9 || this.options.ecmaVersion >= 6 && !isAsync)
+    node.generator = this.eat(tt.star)
+  if (this.options.ecmaVersion >= 8)
+    node.async = !!isAsync
+
+  if (isStatement) {
+    node.id = isStatement === "nullableID" && this.type != tt.name ? null : this.parseIdent()
+    if (node.id) {
+      this.checkLVal(node.id, "var")
+    }
+  }
+
+  let oldInGen = this.inGenerator, oldInAsync = this.inAsync,
+      oldYieldPos = this.yieldPos, oldAwaitPos = this.awaitPos, oldInFunc = this.inFunction
+  this.inGenerator = node.generator
+  this.inAsync = node.async
+  this.yieldPos = 0
+  this.awaitPos = 0
+  this.inFunction = true
+  this.enterFunctionScope()
+
+  if (!isStatement)
+    node.id = this.type == tt.name ? this.parseIdent() : null
+
+  this.parseFunctionParams(node)
+  this.parseFunctionBody(node, allowExpressionBody)
+
+  this.inGenerator = oldInGen
+  this.inAsync = oldInAsync
+  this.yieldPos = oldYieldPos
+  this.awaitPos = oldAwaitPos
+  this.inFunction = oldInFunc
+  return this.finishNode(node, isStatement ? "FunctionDeclaration" : "FunctionExpression")
+}
+
+pp.parseFunctionParams = function(node) {
+  this.expect(tt.parenL)
+  node.params = this.parseBindingList(tt.parenR, false, this.options.ecmaVersion >= 8)
+  this.checkYieldAwaitInDefaultParams()
+}
+
+// Parse a class declaration or literal (depending on the
+// `isStatement` parameter).
+
+pp.parseClass = function(node, isStatement) {
+  this.next()
+
+  this.parseClassId(node, isStatement)
+  this.parseClassSuper(node)
+  let classBody = this.startNode()
+  let hadConstructor = false
+  classBody.body = []
+  this.expect(tt.braceL)
+  while (!this.eat(tt.braceR)) {
+    const member = this.parseClassMember(classBody)
+    if (member && member.type === "MethodDefinition" && member.kind === "constructor") {
+      if (hadConstructor) this.raise(member.start, "Duplicate constructor in the same class")
+      hadConstructor = true
+    }
+  }
+  node.body = this.finishNode(classBody, "ClassBody")
+  return this.finishNode(node, isStatement ? "ClassDeclaration" : "ClassExpression")
+}
+
+pp.parseClassMember = function(classBody) {
+  if (this.eat(tt.semi)) return null
+
+  let method = this.startNode()
+  const tryContextual = (k, noLineBreak = false) => {
+    const start = this.start, startLoc = this.startLoc
+    if (!this.eatContextual(k)) return false
+    if (this.type !== tt.parenL && (!noLineBreak || !this.canInsertSemicolon())) return true
+    if (method.key) this.unexpected()
+    method.computed = false
+    method.key = this.startNodeAt(start, startLoc)
+    method.key.name = k
+    this.finishNode(method.key, "Identifier")
+    return false
+  }
+
+  method.kind = "method"
+  method.static = tryContextual("static")
+  let isGenerator = this.eat(tt.star)
+  let isAsync = false
+  if (!isGenerator) {
+    if (this.options.ecmaVersion >= 8 && tryContextual("async", true)) {
+      isAsync = true
+      isGenerator = this.options.ecmaVersion >= 9 && this.eat(tt.star)
+    } else if (tryContextual("get")) {
+      method.kind = "get"
+    } else if (tryContextual("set")) {
+      method.kind = "set"
+    }
+  }
+  if (!method.key) this.parsePropertyName(method)
+  let {key} = method
+  if (!method.computed && !method.static && (key.type === "Identifier" && key.name === "constructor" ||
+      key.type === "Literal" && key.value === "constructor")) {
+    if (method.kind !== "method") this.raise(key.start, "Constructor can't have get/set modifier")
+    if (isGenerator) this.raise(key.start, "Constructor can't be a generator")
+    if (isAsync) this.raise(key.start, "Constructor can't be an async method")
+    method.kind = "constructor"
+  } else if (method.static && key.type === "Identifier" && key.name === "prototype") {
+    this.raise(key.start, "Classes may not have a static property named prototype")
+  }
+  this.parseClassMethod(classBody, method, isGenerator, isAsync)
+  if (method.kind === "get" && method.value.params.length !== 0)
+    this.raiseRecoverable(method.value.start, "getter should have no params")
+  if (method.kind === "set" && method.value.params.length !== 1)
+    this.raiseRecoverable(method.value.start, "setter should have exactly one param")
+  if (method.kind === "set" && method.value.params[0].type === "RestElement")
+    this.raiseRecoverable(method.value.params[0].start, "Setter cannot use rest params")
+  return method
+}
+
+pp.parseClassMethod = function(classBody, method, isGenerator, isAsync) {
+  method.value = this.parseMethod(isGenerator, isAsync)
+  classBody.body.push(this.finishNode(method, "MethodDefinition"))
+}
+
+pp.parseClassId = function(node, isStatement) {
+  node.id = this.type === tt.name ? this.parseIdent() : isStatement === true ? this.unexpected() : null
+}
+
+pp.parseClassSuper = function(node) {
+  node.superClass = this.eat(tt._extends) ? this.parseExprSubscripts() : null
+}
+
+// Parses module export declaration.
+
+pp.parseExport = function(node, exports) {
+  this.next()
+  // export * from '...'
+  if (this.eat(tt.star)) {
+    this.expectContextual("from")
+    if (this.type !== tt.string) this.unexpected()
+    node.source = this.parseExprAtom()
+    this.semicolon()
+    return this.finishNode(node, "ExportAllDeclaration")
+  }
+  if (this.eat(tt._default)) { // export default ...
+    this.checkExport(exports, "default", this.lastTokStart)
+    let isAsync
+    if (this.type === tt._function || (isAsync = this.isAsyncFunction())) {
+      let fNode = this.startNode()
+      this.next()
+      if (isAsync) this.next()
+      node.declaration = this.parseFunction(fNode, "nullableID", false, isAsync)
+    } else if (this.type === tt._class) {
+      let cNode = this.startNode()
+      node.declaration = this.parseClass(cNode, "nullableID")
+    } else {
+      node.declaration = this.parseMaybeAssign()
+      this.semicolon()
+    }
+    return this.finishNode(node, "ExportDefaultDeclaration")
+  }
+  // export var|const|let|function|class ...
+  if (this.shouldParseExportStatement()) {
+    node.declaration = this.parseStatement(true)
+    if (node.declaration.type === "VariableDeclaration")
+      this.checkVariableExport(exports, node.declaration.declarations)
+    else
+      this.checkExport(exports, node.declaration.id.name, node.declaration.id.start)
+    node.specifiers = []
+    node.source = null
+  } else { // export { x, y as z } [from '...']
+    node.declaration = null
+    node.specifiers = this.parseExportSpecifiers(exports)
+    if (this.eatContextual("from")) {
+      if (this.type !== tt.string) this.unexpected()
+      node.source = this.parseExprAtom()
+    } else {
+      // check for keywords used as local names
+      for (let spec of node.specifiers) {
+        this.checkUnreserved(spec.local)
+      }
+
+      node.source = null
+    }
+    this.semicolon()
+  }
+  return this.finishNode(node, "ExportNamedDeclaration")
+}
+
+pp.checkExport = function(exports, name, pos) {
+  if (!exports) return
+  if (has(exports, name))
+    this.raiseRecoverable(pos, "Duplicate export '" + name + "'")
+  exports[name] = true
+}
+
+pp.checkPatternExport = function(exports, pat) {
+  let type = pat.type
+  if (type == "Identifier")
+    this.checkExport(exports, pat.name, pat.start)
+  else if (type == "ObjectPattern")
+    for (let prop of pat.properties)
+      this.checkPatternExport(exports, prop)
+  else if (type == "ArrayPattern")
+    for (let elt of pat.elements) {
+      if (elt) this.checkPatternExport(exports, elt)
+    }
+  else if (type == "Property")
+    this.checkPatternExport(exports, pat.value)
+  else if (type == "AssignmentPattern")
+    this.checkPatternExport(exports, pat.left)
+  else if (type == "RestElement")
+    this.checkPatternExport(exports, pat.argument)
+  else if (type == "ParenthesizedExpression")
+    this.checkPatternExport(exports, pat.expression)
+}
+
+pp.checkVariableExport = function(exports, decls) {
+  if (!exports) return
+  for (let decl of decls)
+    this.checkPatternExport(exports, decl.id)
+}
+
+pp.shouldParseExportStatement = function() {
+  return this.type.keyword === "var" ||
+    this.type.keyword === "const" ||
+    this.type.keyword === "class" ||
+    this.type.keyword === "function" ||
+    this.isLet() ||
+    this.isAsyncFunction()
+}
+
+// Parses a comma-separated list of module exports.
+
+pp.parseExportSpecifiers = function(exports) {
+  let nodes = [], first = true
+  // export { x, y as z } [from '...']
+  this.expect(tt.braceL)
+  while (!this.eat(tt.braceR)) {
+    if (!first) {
+      this.expect(tt.comma)
+      if (this.afterTrailingComma(tt.braceR)) break
+    } else first = false
+
+    let node = this.startNode()
+    node.local = this.parseIdent(true)
+    node.exported = this.eatContextual("as") ? this.parseIdent(true) : node.local
+    this.checkExport(exports, node.exported.name, node.exported.start)
+    nodes.push(this.finishNode(node, "ExportSpecifier"))
+  }
+  return nodes
+}
+
+// Parses import declaration.
+
+pp.parseImport = function(node) {
+  this.next()
+  // import '...'
+  if (this.type === tt.string) {
+    node.specifiers = empty
+    node.source = this.parseExprAtom()
+  } else {
+    node.specifiers = this.parseImportSpecifiers()
+    this.expectContextual("from")
+    node.source = this.type === tt.string ? this.parseExprAtom() : this.unexpected()
+  }
+  this.semicolon()
+  return this.finishNode(node, "ImportDeclaration")
+}
+
+// Parses a comma-separated list of module imports.
+
+pp.parseImportSpecifiers = function() {
+  let nodes = [], first = true
+  if (this.type === tt.name) {
+    // import defaultObj, { x, y as z } from '...'
+    let node = this.startNode()
+    node.local = this.parseIdent()
+    this.checkLVal(node.local, "let")
+    nodes.push(this.finishNode(node, "ImportDefaultSpecifier"))
+    if (!this.eat(tt.comma)) return nodes
+  }
+  if (this.type === tt.star) {
+    let node = this.startNode()
+    this.next()
+    this.expectContextual("as")
+    node.local = this.parseIdent()
+    this.checkLVal(node.local, "let")
+    nodes.push(this.finishNode(node, "ImportNamespaceSpecifier"))
+    return nodes
+  }
+  this.expect(tt.braceL)
+  while (!this.eat(tt.braceR)) {
+    if (!first) {
+      this.expect(tt.comma)
+      if (this.afterTrailingComma(tt.braceR)) break
+    } else first = false
+
+    let node = this.startNode()
+    node.imported = this.parseIdent(true)
+    if (this.eatContextual("as")) {
+      node.local = this.parseIdent()
+    } else {
+      this.checkUnreserved(node.imported)
+      node.local = node.imported
+    }
+    this.checkLVal(node.local, "let")
+    nodes.push(this.finishNode(node, "ImportSpecifier"))
+  }
+  return nodes
+}
+
+// Set `ExpressionStatement#directive` property for directive prologues.
+pp.adaptDirectivePrologue = function(statements) {
+  for (let i = 0; i < statements.length && this.isDirectiveCandidate(statements[i]); ++i) {
+    statements[i].directive = statements[i].expression.raw.slice(1, -1)
+  }
+}
+pp.isDirectiveCandidate = function(statement) {
+  return (
+    statement.type === "ExpressionStatement" &&
+    statement.expression.type === "Literal" &&
+    typeof statement.expression.value === "string" &&
+    // Reject parenthesized strings.
+    (this.input[statement.start] === "\"" || this.input[statement.start] === "'")
+  )
+}
diff --git a/tools/tests/apps/modules/imports/links/acorn/src/tokencontext.js b/tools/tests/apps/modules/imports/links/acorn/src/tokencontext.js
new file mode 100644
index 0000000000..18dda85ce6
--- /dev/null
+++ b/tools/tests/apps/modules/imports/links/acorn/src/tokencontext.js
@@ -0,0 +1,148 @@
+// The algorithm used to determine whether a regexp can appear at a
+// given point in the program is loosely based on sweet.js' approach.
+// See https://github.com/mozilla/sweet.js/wiki/design
+
+import {Parser} from "./state"
+import {types as tt} from "./tokentype"
+import {lineBreak} from "./whitespace"
+
+export class TokContext {
+  constructor(token, isExpr, preserveSpace, override, generator) {
+    this.token = token
+    this.isExpr = !!isExpr
+    this.preserveSpace = !!preserveSpace
+    this.override = override
+    this.generator = !!generator
+  }
+}
+
+export const types = {
+  b_stat: new TokContext("{", false),
+  b_expr: new TokContext("{", true),
+  b_tmpl: new TokContext("${", false),
+  p_stat: new TokContext("(", false),
+  p_expr: new TokContext("(", true),
+  q_tmpl: new TokContext("`", true, true, p => p.tryReadTemplateToken()),
+  f_stat: new TokContext("function", false),
+  f_expr: new TokContext("function", true),
+  f_expr_gen: new TokContext("function", true, false, null, true),
+  f_gen: new TokContext("function", false, false, null, true)
+}
+
+const pp = Parser.prototype
+
+pp.initialContext = function() {
+  return [types.b_stat]
+}
+
+pp.braceIsBlock = function(prevType) {
+  let parent = this.curContext()
+  if (parent === types.f_expr || parent === types.f_stat)
+    return true
+  if (prevType === tt.colon && (parent === types.b_stat || parent === types.b_expr))
+    return !parent.isExpr
+
+  // The check for `tt.name && exprAllowed` detects whether we are
+  // after a `yield` or `of` construct. See the `updateContext` for
+  // `tt.name`.
+  if (prevType === tt._return || prevType == tt.name && this.exprAllowed)
+    return lineBreak.test(this.input.slice(this.lastTokEnd, this.start))
+  if (prevType === tt._else || prevType === tt.semi || prevType === tt.eof || prevType === tt.parenR || prevType == tt.arrow)
+    return true
+  if (prevType == tt.braceL)
+    return parent === types.b_stat
+  if (prevType == tt._var || prevType == tt.name)
+    return false
+  return !this.exprAllowed
+}
+
+pp.inGeneratorContext = function() {
+  for (let i = this.context.length - 1; i >= 1; i--) {
+    let context = this.context[i]
+    if (context.token === "function")
+      return context.generator
+  }
+  return false
+}
+
+pp.updateContext = function(prevType) {
+  let update, type = this.type
+  if (type.keyword && prevType == tt.dot)
+    this.exprAllowed = false
+  else if (update = type.updateContext)
+    update.call(this, prevType)
+  else
+    this.exprAllowed = type.beforeExpr
+}
+
+// Token-specific context update code
+
+tt.parenR.updateContext = tt.braceR.updateContext = function() {
+  if (this.context.length == 1) {
+    this.exprAllowed = true
+    return
+  }
+  let out = this.context.pop()
+  if (out === types.b_stat && this.curContext().token === "function") {
+    out = this.context.pop()
+  }
+  this.exprAllowed = !out.isExpr
+}
+
+tt.braceL.updateContext = function(prevType) {
+  this.context.push(this.braceIsBlock(prevType) ? types.b_stat : types.b_expr)
+  this.exprAllowed = true
+}
+
+tt.dollarBraceL.updateContext = function() {
+  this.context.push(types.b_tmpl)
+  this.exprAllowed = true
+}
+
+tt.parenL.updateContext = function(prevType) {
+  let statementParens = prevType === tt._if || prevType === tt._for || prevType === tt._with || prevType === tt._while
+  this.context.push(statementParens ? types.p_stat : types.p_expr)
+  this.exprAllowed = true
+}
+
+tt.incDec.updateContext = function() {
+  // tokExprAllowed stays unchanged
+}
+
+tt._function.updateContext = tt._class.updateContext = function(prevType) {
+  if (prevType.beforeExpr && prevType !== tt.semi && prevType !== tt._else &&
+      !((prevType === tt.colon || prevType === tt.braceL) && this.curContext() === types.b_stat))
+    this.context.push(types.f_expr)
+  else
+    this.context.push(types.f_stat)
+  this.exprAllowed = false
+}
+
+tt.backQuote.updateContext = function() {
+  if (this.curContext() === types.q_tmpl)
+    this.context.pop()
+  else
+    this.context.push(types.q_tmpl)
+  this.exprAllowed = false
+}
+
+tt.star.updateContext = function(prevType) {
+  if (prevType == tt._function) {
+    let index = this.context.length - 1
+    if (this.context[index] === types.f_expr)
+      this.context[index] = types.f_expr_gen
+    else
+      this.context[index] = types.f_gen
+  }
+  this.exprAllowed = true
+}
+
+tt.name.updateContext = function(prevType) {
+  let allowed = false
+  if (this.options.ecmaVersion >= 6) {
+    if (this.value == "of" && !this.exprAllowed ||
+        this.value == "yield" && this.inGeneratorContext())
+      allowed = true
+  }
+  this.exprAllowed = allowed
+}
diff --git a/tools/tests/apps/modules/imports/links/acorn/src/tokenize.js b/tools/tests/apps/modules/imports/links/acorn/src/tokenize.js
new file mode 100644
index 0000000000..3afb8386f2
--- /dev/null
+++ b/tools/tests/apps/modules/imports/links/acorn/src/tokenize.js
@@ -0,0 +1,698 @@
+import {isIdentifierStart, isIdentifierChar} from "./identifier"
+import {types as tt, keywords as keywordTypes} from "./tokentype"
+import {Parser} from "./state"
+import {SourceLocation} from "./locutil"
+import {RegExpValidationState} from "./regexp"
+import {lineBreak, lineBreakG, isNewLine, nonASCIIwhitespace} from "./whitespace"
+
+// Object type used to represent tokens. Note that normally, tokens
+// simply exist as properties on the parser object. This is only
+// used for the onToken callback and the external tokenizer.
+
+export class Token {
+  constructor(p) {
+    this.type = p.type
+    this.value = p.value
+    this.start = p.start
+    this.end = p.end
+    if (p.options.locations)
+      this.loc = new SourceLocation(p, p.startLoc, p.endLoc)
+    if (p.options.ranges)
+      this.range = [p.start, p.end]
+  }
+}
+
+// ## Tokenizer
+
+const pp = Parser.prototype
+
+// Move to the next token
+
+pp.next = function() {
+  if (this.options.onToken)
+    this.options.onToken(new Token(this))
+
+  this.lastTokEnd = this.end
+  this.lastTokStart = this.start
+  this.lastTokEndLoc = this.endLoc
+  this.lastTokStartLoc = this.startLoc
+  this.nextToken()
+}
+
+pp.getToken = function() {
+  this.next()
+  return new Token(this)
+}
+
+// If we're in an ES6 environment, make parsers iterable
+if (typeof Symbol !== "undefined")
+  pp[Symbol.iterator] = function() {
+    return {
+      next: () => {
+        let token = this.getToken()
+        return {
+          done: token.type === tt.eof,
+          value: token
+        }
+      }
+    }
+  }
+
+// Toggle strict mode. Re-reads the next number or string to please
+// pedantic tests (`"use strict"; 010;` should fail).
+
+pp.curContext = function() {
+  return this.context[this.context.length - 1]
+}
+
+// Read a single token, updating the parser object's token-related
+// properties.
+
+pp.nextToken = function() {
+  let curContext = this.curContext()
+  if (!curContext || !curContext.preserveSpace) this.skipSpace()
+
+  this.start = this.pos
+  if (this.options.locations) this.startLoc = this.curPosition()
+  if (this.pos >= this.input.length) return this.finishToken(tt.eof)
+
+  if (curContext.override) return curContext.override(this)
+  else this.readToken(this.fullCharCodeAtPos())
+}
+
+pp.readToken = function(code) {
+  // Identifier or keyword. '\uXXXX' sequences are allowed in
+  // identifiers, so '\' also dispatches to that.
+  if (isIdentifierStart(code, this.options.ecmaVersion >= 6) || code === 92 /* '\' */)
+    return this.readWord()
+
+  return this.getTokenFromCode(code)
+}
+
+pp.fullCharCodeAtPos = function() {
+  let code = this.input.charCodeAt(this.pos)
+  if (code <= 0xd7ff || code >= 0xe000) return code
+  let next = this.input.charCodeAt(this.pos + 1)
+  return (code << 10) + next - 0x35fdc00
+}
+
+pp.skipBlockComment = function() {
+  let startLoc = this.options.onComment && this.curPosition()
+  let start = this.pos, end = this.input.indexOf("*/", this.pos += 2)
+  if (end === -1) this.raise(this.pos - 2, "Unterminated comment")
+  this.pos = end + 2
+  if (this.options.locations) {
+    lineBreakG.lastIndex = start
+    let match
+    while ((match = lineBreakG.exec(this.input)) && match.index < this.pos) {
+      ++this.curLine
+      this.lineStart = match.index + match[0].length
+    }
+  }
+  if (this.options.onComment)
+    this.options.onComment(true, this.input.slice(start + 2, end), start, this.pos,
+                           startLoc, this.curPosition())
+}
+
+pp.skipLineComment = function(startSkip) {
+  let start = this.pos
+  let startLoc = this.options.onComment && this.curPosition()
+  let ch = this.input.charCodeAt(this.pos += startSkip)
+  while (this.pos < this.input.length && !isNewLine(ch)) {
+    ch = this.input.charCodeAt(++this.pos)
+  }
+  if (this.options.onComment)
+    this.options.onComment(false, this.input.slice(start + startSkip, this.pos), start, this.pos,
+                           startLoc, this.curPosition())
+}
+
+// Called at the start of the parse and after every token. Skips
+// whitespace and comments, and.
+
+pp.skipSpace = function() {
+  loop: while (this.pos < this.input.length) {
+    let ch = this.input.charCodeAt(this.pos)
+    switch (ch) {
+    case 32: case 160: // ' '
+      ++this.pos
+      break
+    case 13:
+      if (this.input.charCodeAt(this.pos + 1) === 10) {
+        ++this.pos
+      }
+    case 10: case 8232: case 8233:
+      ++this.pos
+      if (this.options.locations) {
+        ++this.curLine
+        this.lineStart = this.pos
+      }
+      break
+    case 47: // '/'
+      switch (this.input.charCodeAt(this.pos + 1)) {
+      case 42: // '*'
+        this.skipBlockComment()
+        break
+      case 47:
+        this.skipLineComment(2)
+        break
+      default:
+        break loop
+      }
+      break
+    default:
+      if (ch > 8 && ch < 14 || ch >= 5760 && nonASCIIwhitespace.test(String.fromCharCode(ch))) {
+        ++this.pos
+      } else {
+        break loop
+      }
+    }
+  }
+}
+
+// Called at the end of every token. Sets `end`, `val`, and
+// maintains `context` and `exprAllowed`, and skips the space after
+// the token, so that the next one's `start` will point at the
+// right position.
+
+pp.finishToken = function(type, val) {
+  this.end = this.pos
+  if (this.options.locations) this.endLoc = this.curPosition()
+  let prevType = this.type
+  this.type = type
+  this.value = val
+
+  this.updateContext(prevType)
+}
+
+// ### Token reading
+
+// This is the function that is called to fetch the next token. It
+// is somewhat obscure, because it works in character codes rather
+// than characters, and because operator parsing has been inlined
+// into it.
+//
+// All in the name of speed.
+//
+pp.readToken_dot = function() {
+  let next = this.input.charCodeAt(this.pos + 1)
+  if (next >= 48 && next <= 57) return this.readNumber(true)
+  let next2 = this.input.charCodeAt(this.pos + 2)
+  if (this.options.ecmaVersion >= 6 && next === 46 && next2 === 46) { // 46 = dot '.'
+    this.pos += 3
+    return this.finishToken(tt.ellipsis)
+  } else {
+    ++this.pos
+    return this.finishToken(tt.dot)
+  }
+}
+
+pp.readToken_slash = function() { // '/'
+  let next = this.input.charCodeAt(this.pos + 1)
+  if (this.exprAllowed) { ++this.pos; return this.readRegexp() }
+  if (next === 61) return this.finishOp(tt.assign, 2)
+  return this.finishOp(tt.slash, 1)
+}
+
+pp.readToken_mult_modulo_exp = function(code) { // '%*'
+  let next = this.input.charCodeAt(this.pos + 1)
+  let size = 1
+  let tokentype = code === 42 ? tt.star : tt.modulo
+
+  // exponentiation operator ** and **=
+  if (this.options.ecmaVersion >= 7 && code == 42 && next === 42) {
+    ++size
+    tokentype = tt.starstar
+    next = this.input.charCodeAt(this.pos + 2)
+  }
+
+  if (next === 61) return this.finishOp(tt.assign, size + 1)
+  return this.finishOp(tokentype, size)
+}
+
+pp.readToken_pipe_amp = function(code) { // '|&'
+  let next = this.input.charCodeAt(this.pos + 1)
+  if (next === code) return this.finishOp(code === 124 ? tt.logicalOR : tt.logicalAND, 2)
+  if (next === 61) return this.finishOp(tt.assign, 2)
+  return this.finishOp(code === 124 ? tt.bitwiseOR : tt.bitwiseAND, 1)
+}
+
+pp.readToken_caret = function() { // '^'
+  let next = this.input.charCodeAt(this.pos + 1)
+  if (next === 61) return this.finishOp(tt.assign, 2)
+  return this.finishOp(tt.bitwiseXOR, 1)
+}
+
+pp.readToken_plus_min = function(code) { // '+-'
+  let next = this.input.charCodeAt(this.pos + 1)
+  if (next === code) {
+    if (next == 45 && !this.inModule && this.input.charCodeAt(this.pos + 2) == 62 &&
+        (this.lastTokEnd === 0 || lineBreak.test(this.input.slice(this.lastTokEnd, this.pos)))) {
+      // A `-->` line comment
+      this.skipLineComment(3)
+      this.skipSpace()
+      return this.nextToken()
+    }
+    return this.finishOp(tt.incDec, 2)
+  }
+  if (next === 61) return this.finishOp(tt.assign, 2)
+  return this.finishOp(tt.plusMin, 1)
+}
+
+pp.readToken_lt_gt = function(code) { // '<>'
+  let next = this.input.charCodeAt(this.pos + 1)
+  let size = 1
+  if (next === code) {
+    size = code === 62 && this.input.charCodeAt(this.pos + 2) === 62 ? 3 : 2
+    if (this.input.charCodeAt(this.pos + size) === 61) return this.finishOp(tt.assign, size + 1)
+    return this.finishOp(tt.bitShift, size)
+  }
+  if (next == 33 && code == 60 && !this.inModule && this.input.charCodeAt(this.pos + 2) == 45 &&
+      this.input.charCodeAt(this.pos + 3) == 45) {
+    // `<!--`, an XML-style comment that should be interpreted as a line comment
+    this.skipLineComment(4)
+    this.skipSpace()
+    return this.nextToken()
+  }
+  if (next === 61) size = 2
+  return this.finishOp(tt.relational, size)
+}
+
+pp.readToken_eq_excl = function(code) { // '=!'
+  let next = this.input.charCodeAt(this.pos + 1)
+  if (next === 61) return this.finishOp(tt.equality, this.input.charCodeAt(this.pos + 2) === 61 ? 3 : 2)
+  if (code === 61 && next === 62 && this.options.ecmaVersion >= 6) { // '=>'
+    this.pos += 2
+    return this.finishToken(tt.arrow)
+  }
+  return this.finishOp(code === 61 ? tt.eq : tt.prefix, 1)
+}
+
+pp.getTokenFromCode = function(code) {
+  switch (code) {
+  // The interpretation of a dot depends on whether it is followed
+  // by a digit or another two dots.
+  case 46: // '.'
+    return this.readToken_dot()
+
+  // Punctuation tokens.
+  case 40: ++this.pos; return this.finishToken(tt.parenL)
+  case 41: ++this.pos; return this.finishToken(tt.parenR)
+  case 59: ++this.pos; return this.finishToken(tt.semi)
+  case 44: ++this.pos; return this.finishToken(tt.comma)
+  case 91: ++this.pos; return this.finishToken(tt.bracketL)
+  case 93: ++this.pos; return this.finishToken(tt.bracketR)
+  case 123: ++this.pos; return this.finishToken(tt.braceL)
+  case 125: ++this.pos; return this.finishToken(tt.braceR)
+  case 58: ++this.pos; return this.finishToken(tt.colon)
+  case 63: ++this.pos; return this.finishToken(tt.question)
+
+  case 96: // '`'
+    if (this.options.ecmaVersion < 6) break
+    ++this.pos
+    return this.finishToken(tt.backQuote)
+
+  case 48: // '0'
+    let next = this.input.charCodeAt(this.pos + 1)
+    if (next === 120 || next === 88) return this.readRadixNumber(16) // '0x', '0X' - hex number
+    if (this.options.ecmaVersion >= 6) {
+      if (next === 111 || next === 79) return this.readRadixNumber(8) // '0o', '0O' - octal number
+      if (next === 98 || next === 66) return this.readRadixNumber(2) // '0b', '0B' - binary number
+    }
+
+  // Anything else beginning with a digit is an integer, octal
+  // number, or float.
+  case 49: case 50: case 51: case 52: case 53: case 54: case 55: case 56: case 57: // 1-9
+    return this.readNumber(false)
+
+  // Quotes produce strings.
+  case 34: case 39: // '"', "'"
+    return this.readString(code)
+
+  // Operators are parsed inline in tiny state machines. '=' (61) is
+  // often referred to. `finishOp` simply skips the amount of
+  // characters it is given as second argument, and returns a token
+  // of the type given by its first argument.
+
+  case 47: // '/'
+    return this.readToken_slash()
+
+  case 37: case 42: // '%*'
+    return this.readToken_mult_modulo_exp(code)
+
+  case 124: case 38: // '|&'
+    return this.readToken_pipe_amp(code)
+
+  case 94: // '^'
+    return this.readToken_caret()
+
+  case 43: case 45: // '+-'
+    return this.readToken_plus_min(code)
+
+  case 60: case 62: // '<>'
+    return this.readToken_lt_gt(code)
+
+  case 61: case 33: // '=!'
+    return this.readToken_eq_excl(code)
+
+  case 126: // '~'
+    return this.finishOp(tt.prefix, 1)
+  }
+
+  this.raise(this.pos, "Unexpected character '" + codePointToString(code) + "'")
+}
+
+pp.finishOp = function(type, size) {
+  let str = this.input.slice(this.pos, this.pos + size)
+  this.pos += size
+  return this.finishToken(type, str)
+}
+
+pp.readRegexp = function() {
+  let escaped, inClass, start = this.pos
+  for (;;) {
+    if (this.pos >= this.input.length) this.raise(start, "Unterminated regular expression")
+    let ch = this.input.charAt(this.pos)
+    if (lineBreak.test(ch)) this.raise(start, "Unterminated regular expression")
+    if (!escaped) {
+      if (ch === "[") inClass = true
+      else if (ch === "]" && inClass) inClass = false
+      else if (ch === "/" && !inClass) break
+      escaped = ch === "\\"
+    } else escaped = false
+    ++this.pos
+  }
+  let pattern = this.input.slice(start, this.pos)
+  ++this.pos
+  let flagsStart = this.pos
+  let flags = this.readWord1()
+  if (this.containsEsc) this.unexpected(flagsStart)
+
+  // Validate pattern
+  const state = this.regexpState || (this.regexpState = new RegExpValidationState(this))
+  state.reset(start, pattern, flags)
+  this.validateRegExpFlags(state)
+  this.validateRegExpPattern(state)
+
+  // Create Literal#value property value.
+  let value = null
+  try {
+    value = new RegExp(pattern, flags)
+  } catch (e) {
+    // ESTree requires null if it failed to instantiate RegExp object.
+    // https://github.com/estree/estree/blob/a27003adf4fd7bfad44de9cef372a2eacd527b1c/es5.md#regexpliteral
+  }
+
+  return this.finishToken(tt.regexp, {pattern, flags, value})
+}
+
+// Read an integer in the given radix. Return null if zero digits
+// were read, the integer value otherwise. When `len` is given, this
+// will return `null` unless the integer has exactly `len` digits.
+
+pp.readInt = function(radix, len) {
+  let start = this.pos, total = 0
+  for (let i = 0, e = len == null ? Infinity : len; i < e; ++i) {
+    let code = this.input.charCodeAt(this.pos), val
+    if (code >= 97) val = code - 97 + 10 // a
+    else if (code >= 65) val = code - 65 + 10 // A
+    else if (code >= 48 && code <= 57) val = code - 48 // 0-9
+    else val = Infinity
+    if (val >= radix) break
+    ++this.pos
+    total = total * radix + val
+  }
+  if (this.pos === start || len != null && this.pos - start !== len) return null
+
+  return total
+}
+
+pp.readRadixNumber = function(radix) {
+  this.pos += 2 // 0x
+  let val = this.readInt(radix)
+  if (val == null) this.raise(this.start + 2, "Expected number in radix " + radix)
+  if (isIdentifierStart(this.fullCharCodeAtPos())) this.raise(this.pos, "Identifier directly after number")
+  return this.finishToken(tt.num, val)
+}
+
+// Read an integer, octal integer, or floating-point number.
+
+pp.readNumber = function(startsWithDot) {
+  let start = this.pos
+  if (!startsWithDot && this.readInt(10) === null) this.raise(start, "Invalid number")
+  let octal = this.pos - start >= 2 && this.input.charCodeAt(start) === 48
+  if (octal && this.strict) this.raise(start, "Invalid number")
+  if (octal && /[89]/.test(this.input.slice(start, this.pos))) octal = false
+  let next = this.input.charCodeAt(this.pos)
+  if (next === 46 && !octal) { // '.'
+    ++this.pos
+    this.readInt(10)
+    next = this.input.charCodeAt(this.pos)
+  }
+  if ((next === 69 || next === 101) && !octal) { // 'eE'
+    next = this.input.charCodeAt(++this.pos)
+    if (next === 43 || next === 45) ++this.pos // '+-'
+    if (this.readInt(10) === null) this.raise(start, "Invalid number")
+  }
+  if (isIdentifierStart(this.fullCharCodeAtPos())) this.raise(this.pos, "Identifier directly after number")
+
+  let str = this.input.slice(start, this.pos)
+  let val = octal ? parseInt(str, 8) : parseFloat(str)
+  return this.finishToken(tt.num, val)
+}
+
+// Read a string value, interpreting backslash-escapes.
+
+pp.readCodePoint = function() {
+  let ch = this.input.charCodeAt(this.pos), code
+
+  if (ch === 123) { // '{'
+    if (this.options.ecmaVersion < 6) this.unexpected()
+    let codePos = ++this.pos
+    code = this.readHexChar(this.input.indexOf("}", this.pos) - this.pos)
+    ++this.pos
+    if (code > 0x10FFFF) this.invalidStringToken(codePos, "Code point out of bounds")
+  } else {
+    code = this.readHexChar(4)
+  }
+  return code
+}
+
+function codePointToString(code) {
+  // UTF-16 Decoding
+  if (code <= 0xFFFF) return String.fromCharCode(code)
+  code -= 0x10000
+  return String.fromCharCode((code >> 10) + 0xD800, (code & 1023) + 0xDC00)
+}
+
+pp.readString = function(quote) {
+  let out = "", chunkStart = ++this.pos
+  for (;;) {
+    if (this.pos >= this.input.length) this.raise(this.start, "Unterminated string constant")
+    let ch = this.input.charCodeAt(this.pos)
+    if (ch === quote) break
+    if (ch === 92) { // '\'
+      out += this.input.slice(chunkStart, this.pos)
+      out += this.readEscapedChar(false)
+      chunkStart = this.pos
+    } else {
+      if (isNewLine(ch)) this.raise(this.start, "Unterminated string constant")
+      ++this.pos
+    }
+  }
+  out += this.input.slice(chunkStart, this.pos++)
+  return this.finishToken(tt.string, out)
+}
+
+// Reads template string tokens.
+
+const INVALID_TEMPLATE_ESCAPE_ERROR = {}
+
+pp.tryReadTemplateToken = function() {
+  this.inTemplateElement = true
+  try {
+    this.readTmplToken()
+  } catch (err) {
+    if (err === INVALID_TEMPLATE_ESCAPE_ERROR) {
+      this.readInvalidTemplateToken()
+    } else {
+      throw err
+    }
+  }
+
+  this.inTemplateElement = false
+}
+
+pp.invalidStringToken = function(position, message) {
+  if (this.inTemplateElement && this.options.ecmaVersion >= 9) {
+    throw INVALID_TEMPLATE_ESCAPE_ERROR
+  } else {
+    this.raise(position, message)
+  }
+}
+
+pp.readTmplToken = function() {
+  let out = "", chunkStart = this.pos
+  for (;;) {
+    if (this.pos >= this.input.length) this.raise(this.start, "Unterminated template")
+    let ch = this.input.charCodeAt(this.pos)
+    if (ch === 96 || ch === 36 && this.input.charCodeAt(this.pos + 1) === 123) { // '`', '${'
+      if (this.pos === this.start && (this.type === tt.template || this.type === tt.invalidTemplate)) {
+        if (ch === 36) {
+          this.pos += 2
+          return this.finishToken(tt.dollarBraceL)
+        } else {
+          ++this.pos
+          return this.finishToken(tt.backQuote)
+        }
+      }
+      out += this.input.slice(chunkStart, this.pos)
+      return this.finishToken(tt.template, out)
+    }
+    if (ch === 92) { // '\'
+      out += this.input.slice(chunkStart, this.pos)
+      out += this.readEscapedChar(true)
+      chunkStart = this.pos
+    } else if (isNewLine(ch)) {
+      out += this.input.slice(chunkStart, this.pos)
+      ++this.pos
+      switch (ch) {
+      case 13:
+        if (this.input.charCodeAt(this.pos) === 10) ++this.pos
+      case 10:
+        out += "\n"
+        break
+      default:
+        out += String.fromCharCode(ch)
+        break
+      }
+      if (this.options.locations) {
+        ++this.curLine
+        this.lineStart = this.pos
+      }
+      chunkStart = this.pos
+    } else {
+      ++this.pos
+    }
+  }
+}
+
+// Reads a template token to search for the end, without validating any escape sequences
+pp.readInvalidTemplateToken = function() {
+  for (; this.pos < this.input.length; this.pos++) {
+    switch (this.input[this.pos]) {
+    case "\\":
+      ++this.pos
+      break
+
+    case "$":
+      if (this.input[this.pos + 1] !== "{") {
+        break
+      }
+    // falls through
+
+    case "`":
+      return this.finishToken(tt.invalidTemplate, this.input.slice(this.start, this.pos))
+
+    // no default
+    }
+  }
+  this.raise(this.start, "Unterminated template")
+}
+
+// Used to read escaped characters
+
+pp.readEscapedChar = function(inTemplate) {
+  let ch = this.input.charCodeAt(++this.pos)
+  ++this.pos
+  switch (ch) {
+  case 110: return "\n" // 'n' -> '\n'
+  case 114: return "\r" // 'r' -> '\r'
+  case 120: return String.fromCharCode(this.readHexChar(2)) // 'x'
+  case 117: return codePointToString(this.readCodePoint()) // 'u'
+  case 116: return "\t" // 't' -> '\t'
+  case 98: return "\b" // 'b' -> '\b'
+  case 118: return "\u000b" // 'v' -> '\u000b'
+  case 102: return "\f" // 'f' -> '\f'
+  case 13: if (this.input.charCodeAt(this.pos) === 10) ++this.pos // '\r\n'
+  case 10: // ' \n'
+    if (this.options.locations) { this.lineStart = this.pos; ++this.curLine }
+    return ""
+  default:
+    if (ch >= 48 && ch <= 55) {
+      let octalStr = this.input.substr(this.pos - 1, 3).match(/^[0-7]+/)[0]
+      let octal = parseInt(octalStr, 8)
+      if (octal > 255) {
+        octalStr = octalStr.slice(0, -1)
+        octal = parseInt(octalStr, 8)
+      }
+      this.pos += octalStr.length - 1
+      ch = this.input.charCodeAt(this.pos)
+      if ((octalStr !== "0" || ch == 56 || ch == 57) && (this.strict || inTemplate)) {
+        this.invalidStringToken(
+          this.pos - 1 - octalStr.length,
+          inTemplate
+            ? "Octal literal in template string"
+            : "Octal literal in strict mode"
+        )
+      }
+      return String.fromCharCode(octal)
+    }
+    return String.fromCharCode(ch)
+  }
+}
+
+// Used to read character escape sequences ('\x', '\u', '\U').
+
+pp.readHexChar = function(len) {
+  let codePos = this.pos
+  let n = this.readInt(16, len)
+  if (n === null) this.invalidStringToken(codePos, "Bad character escape sequence")
+  return n
+}
+
+// Read an identifier, and return it as a string. Sets `this.containsEsc`
+// to whether the word contained a '\u' escape.
+//
+// Incrementally adds only escaped chars, adding other chunks as-is
+// as a micro-optimization.
+
+pp.readWord1 = function() {
+  this.containsEsc = false
+  let word = "", first = true, chunkStart = this.pos
+  let astral = this.options.ecmaVersion >= 6
+  while (this.pos < this.input.length) {
+    let ch = this.fullCharCodeAtPos()
+    if (isIdentifierChar(ch, astral)) {
+      this.pos += ch <= 0xffff ? 1 : 2
+    } else if (ch === 92) { // "\"
+      this.containsEsc = true
+      word += this.input.slice(chunkStart, this.pos)
+      let escStart = this.pos
+      if (this.input.charCodeAt(++this.pos) != 117) // "u"
+        this.invalidStringToken(this.pos, "Expecting Unicode escape sequence \\uXXXX")
+      ++this.pos
+      let esc = this.readCodePoint()
+      if (!(first ? isIdentifierStart : isIdentifierChar)(esc, astral))
+        this.invalidStringToken(escStart, "Invalid Unicode escape")
+      word += codePointToString(esc)
+      chunkStart = this.pos
+    } else {
+      break
+    }
+    first = false
+  }
+  return word + this.input.slice(chunkStart, this.pos)
+}
+
+// Read an identifier or keyword token. Will check for reserved
+// words when necessary.
+
+pp.readWord = function() {
+  let word = this.readWord1()
+  let type = tt.name
+  if (this.keywords.test(word)) {
+    if (this.containsEsc) this.raiseRecoverable(this.start, "Escape sequence in keyword " + word)
+    type = keywordTypes[word]
+  }
+  return this.finishToken(type, word)
+}
diff --git a/tools/tests/apps/modules/imports/links/acorn/src/tokentype.js b/tools/tests/apps/modules/imports/links/acorn/src/tokentype.js
new file mode 100644
index 0000000000..76b145fda8
--- /dev/null
+++ b/tools/tests/apps/modules/imports/links/acorn/src/tokentype.js
@@ -0,0 +1,148 @@
+// ## Token types
+
+// The assignment of fine-grained, information-carrying type objects
+// allows the tokenizer to store the information it has about a
+// token in a way that is very cheap for the parser to look up.
+
+// All token type variables start with an underscore, to make them
+// easy to recognize.
+
+// The `beforeExpr` property is used to disambiguate between regular
+// expressions and divisions. It is set on all token types that can
+// be followed by an expression (thus, a slash after them would be a
+// regular expression).
+//
+// The `startsExpr` property is used to check if the token ends a
+// `yield` expression. It is set on all token types that either can
+// directly start an expression (like a quotation mark) or can
+// continue an expression (like the body of a string).
+//
+// `isLoop` marks a keyword as starting a loop, which is important
+// to know when parsing a label, in order to allow or disallow
+// continue jumps to that label.
+
+export class TokenType {
+  constructor(label, conf = {}) {
+    this.label = label
+    this.keyword = conf.keyword
+    this.beforeExpr = !!conf.beforeExpr
+    this.startsExpr = !!conf.startsExpr
+    this.isLoop = !!conf.isLoop
+    this.isAssign = !!conf.isAssign
+    this.prefix = !!conf.prefix
+    this.postfix = !!conf.postfix
+    this.binop = conf.binop || null
+    this.updateContext = null
+  }
+}
+
+function binop(name, prec) {
+  return new TokenType(name, {beforeExpr: true, binop: prec})
+}
+const beforeExpr = {beforeExpr: true}, startsExpr = {startsExpr: true}
+
+// Map keyword names to token types.
+
+export const keywords = {}
+
+// Succinct definitions of keyword token types
+function kw(name, options = {}) {
+  options.keyword = name
+  return keywords[name] = new TokenType(name, options)
+}
+
+export const types = {
+  num: new TokenType("num", startsExpr),
+  regexp: new TokenType("regexp", startsExpr),
+  string: new TokenType("string", startsExpr),
+  name: new TokenType("name", startsExpr),
+  eof: new TokenType("eof"),
+
+  // Punctuation token types.
+  bracketL: new TokenType("[", {beforeExpr: true, startsExpr: true}),
+  bracketR: new TokenType("]"),
+  braceL: new TokenType("{", {beforeExpr: true, startsExpr: true}),
+  braceR: new TokenType("}"),
+  parenL: new TokenType("(", {beforeExpr: true, startsExpr: true}),
+  parenR: new TokenType(")"),
+  comma: new TokenType(",", beforeExpr),
+  semi: new TokenType(";", beforeExpr),
+  colon: new TokenType(":", beforeExpr),
+  dot: new TokenType("."),
+  question: new TokenType("?", beforeExpr),
+  arrow: new TokenType("=>", beforeExpr),
+  template: new TokenType("template"),
+  invalidTemplate: new TokenType("invalidTemplate"),
+  ellipsis: new TokenType("...", beforeExpr),
+  backQuote: new TokenType("`", startsExpr),
+  dollarBraceL: new TokenType("${", {beforeExpr: true, startsExpr: true}),
+
+  // Operators. These carry several kinds of properties to help the
+  // parser use them properly (the presence of these properties is
+  // what categorizes them as operators).
+  //
+  // `binop`, when present, specifies that this operator is a binary
+  // operator, and will refer to its precedence.
+  //
+  // `prefix` and `postfix` mark the operator as a prefix or postfix
+  // unary operator.
+  //
+  // `isAssign` marks all of `=`, `+=`, `-=` etcetera, which act as
+  // binary operators with a very low precedence, that should result
+  // in AssignmentExpression nodes.
+
+  eq: new TokenType("=", {beforeExpr: true, isAssign: true}),
+  assign: new TokenType("_=", {beforeExpr: true, isAssign: true}),
+  incDec: new TokenType("++/--", {prefix: true, postfix: true, startsExpr: true}),
+  prefix: new TokenType("!/~", {beforeExpr: true, prefix: true, startsExpr: true}),
+  logicalOR: binop("||", 1),
+  logicalAND: binop("&&", 2),
+  bitwiseOR: binop("|", 3),
+  bitwiseXOR: binop("^", 4),
+  bitwiseAND: binop("&", 5),
+  equality: binop("==/!=/===/!==", 6),
+  relational: binop("</>/<=/>=", 7),
+  bitShift: binop("<</>>/>>>", 8),
+  plusMin: new TokenType("+/-", {beforeExpr: true, binop: 9, prefix: true, startsExpr: true}),
+  modulo: binop("%", 10),
+  star: binop("*", 10),
+  slash: binop("/", 10),
+  starstar: new TokenType("**", {beforeExpr: true}),
+
+  // Keyword token types.
+  _break: kw("break"),
+  _case: kw("case", beforeExpr),
+  _catch: kw("catch"),
+  _continue: kw("continue"),
+  _debugger: kw("debugger"),
+  _default: kw("default", beforeExpr),
+  _do: kw("do", {isLoop: true, beforeExpr: true}),
+  _else: kw("else", beforeExpr),
+  _finally: kw("finally"),
+  _for: kw("for", {isLoop: true}),
+  _function: kw("function", startsExpr),
+  _if: kw("if"),
+  _return: kw("return", beforeExpr),
+  _switch: kw("switch"),
+  _throw: kw("throw", beforeExpr),
+  _try: kw("try"),
+  _var: kw("var"),
+  _const: kw("const"),
+  _while: kw("while", {isLoop: true}),
+  _with: kw("with"),
+  _new: kw("new", {beforeExpr: true, startsExpr: true}),
+  _this: kw("this", startsExpr),
+  _super: kw("super", startsExpr),
+  _class: kw("class", startsExpr),
+  _extends: kw("extends", beforeExpr),
+  _export: kw("export"),
+  _import: kw("import"),
+  _null: kw("null", startsExpr),
+  _true: kw("true", startsExpr),
+  _false: kw("false", startsExpr),
+  _in: kw("in", {beforeExpr: true, binop: 7}),
+  _instanceof: kw("instanceof", {beforeExpr: true, binop: 7}),
+  _typeof: kw("typeof", {beforeExpr: true, prefix: true, startsExpr: true}),
+  _void: kw("void", {beforeExpr: true, prefix: true, startsExpr: true}),
+  _delete: kw("delete", {beforeExpr: true, prefix: true, startsExpr: true})
+}
diff --git a/tools/tests/apps/modules/imports/links/acorn/src/unicode-property-data.js b/tools/tests/apps/modules/imports/links/acorn/src/unicode-property-data.js
new file mode 100644
index 0000000000..d44f1a2c19
--- /dev/null
+++ b/tools/tests/apps/modules/imports/links/acorn/src/unicode-property-data.js
@@ -0,0 +1,463 @@
+const data = {
+  "$LONE": [
+    "ASCII",
+    "ASCII_Hex_Digit",
+    "AHex",
+    "Alphabetic",
+    "Alpha",
+    "Any",
+    "Assigned",
+    "Bidi_Control",
+    "Bidi_C",
+    "Bidi_Mirrored",
+    "Bidi_M",
+    "Case_Ignorable",
+    "CI",
+    "Cased",
+    "Changes_When_Casefolded",
+    "CWCF",
+    "Changes_When_Casemapped",
+    "CWCM",
+    "Changes_When_Lowercased",
+    "CWL",
+    "Changes_When_NFKC_Casefolded",
+    "CWKCF",
+    "Changes_When_Titlecased",
+    "CWT",
+    "Changes_When_Uppercased",
+    "CWU",
+    "Dash",
+    "Default_Ignorable_Code_Point",
+    "DI",
+    "Deprecated",
+    "Dep",
+    "Diacritic",
+    "Dia",
+    "Emoji",
+    "Emoji_Component",
+    "Emoji_Modifier",
+    "Emoji_Modifier_Base",
+    "Emoji_Presentation",
+    "Extender",
+    "Ext",
+    "Grapheme_Base",
+    "Gr_Base",
+    "Grapheme_Extend",
+    "Gr_Ext",
+    "Hex_Digit",
+    "Hex",
+    "IDS_Binary_Operator",
+    "IDSB",
+    "IDS_Trinary_Operator",
+    "IDST",
+    "ID_Continue",
+    "IDC",
+    "ID_Start",
+    "IDS",
+    "Ideographic",
+    "Ideo",
+    "Join_Control",
+    "Join_C",
+    "Logical_Order_Exception",
+    "LOE",
+    "Lowercase",
+    "Lower",
+    "Math",
+    "Noncharacter_Code_Point",
+    "NChar",
+    "Pattern_Syntax",
+    "Pat_Syn",
+    "Pattern_White_Space",
+    "Pat_WS",
+    "Quotation_Mark",
+    "QMark",
+    "Radical",
+    "Regional_Indicator",
+    "RI",
+    "Sentence_Terminal",
+    "STerm",
+    "Soft_Dotted",
+    "SD",
+    "Terminal_Punctuation",
+    "Term",
+    "Unified_Ideograph",
+    "UIdeo",
+    "Uppercase",
+    "Upper",
+    "Variation_Selector",
+    "VS",
+    "White_Space",
+    "space",
+    "XID_Continue",
+    "XIDC",
+    "XID_Start",
+    "XIDS"
+  ],
+  "General_Category": [
+    "Cased_Letter",
+    "LC",
+    "Close_Punctuation",
+    "Pe",
+    "Connector_Punctuation",
+    "Pc",
+    "Control",
+    "Cc",
+    "cntrl",
+    "Currency_Symbol",
+    "Sc",
+    "Dash_Punctuation",
+    "Pd",
+    "Decimal_Number",
+    "Nd",
+    "digit",
+    "Enclosing_Mark",
+    "Me",
+    "Final_Punctuation",
+    "Pf",
+    "Format",
+    "Cf",
+    "Initial_Punctuation",
+    "Pi",
+    "Letter",
+    "L",
+    "Letter_Number",
+    "Nl",
+    "Line_Separator",
+    "Zl",
+    "Lowercase_Letter",
+    "Ll",
+    "Mark",
+    "M",
+    "Combining_Mark",
+    "Math_Symbol",
+    "Sm",
+    "Modifier_Letter",
+    "Lm",
+    "Modifier_Symbol",
+    "Sk",
+    "Nonspacing_Mark",
+    "Mn",
+    "Number",
+    "N",
+    "Open_Punctuation",
+    "Ps",
+    "Other",
+    "C",
+    "Other_Letter",
+    "Lo",
+    "Other_Number",
+    "No",
+    "Other_Punctuation",
+    "Po",
+    "Other_Symbol",
+    "So",
+    "Paragraph_Separator",
+    "Zp",
+    "Private_Use",
+    "Co",
+    "Punctuation",
+    "P",
+    "punct",
+    "Separator",
+    "Z",
+    "Space_Separator",
+    "Zs",
+    "Spacing_Mark",
+    "Mc",
+    "Surrogate",
+    "Cs",
+    "Symbol",
+    "S",
+    "Titlecase_Letter",
+    "Lt",
+    "Unassigned",
+    "Cn",
+    "Uppercase_Letter",
+    "Lu"
+  ],
+  "Script": [
+    "Adlam",
+    "Adlm",
+    "Ahom",
+    "Anatolian_Hieroglyphs",
+    "Hluw",
+    "Arabic",
+    "Arab",
+    "Armenian",
+    "Armn",
+    "Avestan",
+    "Avst",
+    "Balinese",
+    "Bali",
+    "Bamum",
+    "Bamu",
+    "Bassa_Vah",
+    "Bass",
+    "Batak",
+    "Batk",
+    "Bengali",
+    "Beng",
+    "Bhaiksuki",
+    "Bhks",
+    "Bopomofo",
+    "Bopo",
+    "Brahmi",
+    "Brah",
+    "Braille",
+    "Brai",
+    "Buginese",
+    "Bugi",
+    "Buhid",
+    "Buhd",
+    "Canadian_Aboriginal",
+    "Cans",
+    "Carian",
+    "Cari",
+    "Caucasian_Albanian",
+    "Aghb",
+    "Chakma",
+    "Cakm",
+    "Cham",
+    "Cherokee",
+    "Cher",
+    "Common",
+    "Zyyy",
+    "Coptic",
+    "Copt",
+    "Qaac",
+    "Cuneiform",
+    "Xsux",
+    "Cypriot",
+    "Cprt",
+    "Cyrillic",
+    "Cyrl",
+    "Deseret",
+    "Dsrt",
+    "Devanagari",
+    "Deva",
+    "Duployan",
+    "Dupl",
+    "Egyptian_Hieroglyphs",
+    "Egyp",
+    "Elbasan",
+    "Elba",
+    "Ethiopic",
+    "Ethi",
+    "Georgian",
+    "Geor",
+    "Glagolitic",
+    "Glag",
+    "Gothic",
+    "Goth",
+    "Grantha",
+    "Gran",
+    "Greek",
+    "Grek",
+    "Gujarati",
+    "Gujr",
+    "Gurmukhi",
+    "Guru",
+    "Han",
+    "Hani",
+    "Hangul",
+    "Hang",
+    "Hanunoo",
+    "Hano",
+    "Hatran",
+    "Hatr",
+    "Hebrew",
+    "Hebr",
+    "Hiragana",
+    "Hira",
+    "Imperial_Aramaic",
+    "Armi",
+    "Inherited",
+    "Zinh",
+    "Qaai",
+    "Inscriptional_Pahlavi",
+    "Phli",
+    "Inscriptional_Parthian",
+    "Prti",
+    "Javanese",
+    "Java",
+    "Kaithi",
+    "Kthi",
+    "Kannada",
+    "Knda",
+    "Katakana",
+    "Kana",
+    "Kayah_Li",
+    "Kali",
+    "Kharoshthi",
+    "Khar",
+    "Khmer",
+    "Khmr",
+    "Khojki",
+    "Khoj",
+    "Khudawadi",
+    "Sind",
+    "Lao",
+    "Laoo",
+    "Latin",
+    "Latn",
+    "Lepcha",
+    "Lepc",
+    "Limbu",
+    "Limb",
+    "Linear_A",
+    "Lina",
+    "Linear_B",
+    "Linb",
+    "Lisu",
+    "Lycian",
+    "Lyci",
+    "Lydian",
+    "Lydi",
+    "Mahajani",
+    "Mahj",
+    "Malayalam",
+    "Mlym",
+    "Mandaic",
+    "Mand",
+    "Manichaean",
+    "Mani",
+    "Marchen",
+    "Marc",
+    "Masaram_Gondi",
+    "Gonm",
+    "Meetei_Mayek",
+    "Mtei",
+    "Mende_Kikakui",
+    "Mend",
+    "Meroitic_Cursive",
+    "Merc",
+    "Meroitic_Hieroglyphs",
+    "Mero",
+    "Miao",
+    "Plrd",
+    "Modi",
+    "Mongolian",
+    "Mong",
+    "Mro",
+    "Mroo",
+    "Multani",
+    "Mult",
+    "Myanmar",
+    "Mymr",
+    "Nabataean",
+    "Nbat",
+    "New_Tai_Lue",
+    "Talu",
+    "Newa",
+    "Nko",
+    "Nkoo",
+    "Nushu",
+    "Nshu",
+    "Ogham",
+    "Ogam",
+    "Ol_Chiki",
+    "Olck",
+    "Old_Hungarian",
+    "Hung",
+    "Old_Italic",
+    "Ital",
+    "Old_North_Arabian",
+    "Narb",
+    "Old_Permic",
+    "Perm",
+    "Old_Persian",
+    "Xpeo",
+    "Old_South_Arabian",
+    "Sarb",
+    "Old_Turkic",
+    "Orkh",
+    "Oriya",
+    "Orya",
+    "Osage",
+    "Osge",
+    "Osmanya",
+    "Osma",
+    "Pahawh_Hmong",
+    "Hmng",
+    "Palmyrene",
+    "Palm",
+    "Pau_Cin_Hau",
+    "Pauc",
+    "Phags_Pa",
+    "Phag",
+    "Phoenician",
+    "Phnx",
+    "Psalter_Pahlavi",
+    "Phlp",
+    "Rejang",
+    "Rjng",
+    "Runic",
+    "Runr",
+    "Samaritan",
+    "Samr",
+    "Saurashtra",
+    "Saur",
+    "Sharada",
+    "Shrd",
+    "Shavian",
+    "Shaw",
+    "Siddham",
+    "Sidd",
+    "SignWriting",
+    "Sgnw",
+    "Sinhala",
+    "Sinh",
+    "Sora_Sompeng",
+    "Sora",
+    "Soyombo",
+    "Soyo",
+    "Sundanese",
+    "Sund",
+    "Syloti_Nagri",
+    "Sylo",
+    "Syriac",
+    "Syrc",
+    "Tagalog",
+    "Tglg",
+    "Tagbanwa",
+    "Tagb",
+    "Tai_Le",
+    "Tale",
+    "Tai_Tham",
+    "Lana",
+    "Tai_Viet",
+    "Tavt",
+    "Takri",
+    "Takr",
+    "Tamil",
+    "Taml",
+    "Tangut",
+    "Tang",
+    "Telugu",
+    "Telu",
+    "Thaana",
+    "Thaa",
+    "Thai",
+    "Tibetan",
+    "Tibt",
+    "Tifinagh",
+    "Tfng",
+    "Tirhuta",
+    "Tirh",
+    "Ugaritic",
+    "Ugar",
+    "Vai",
+    "Vaii",
+    "Warang_Citi",
+    "Wara",
+    "Yi",
+    "Yiii",
+    "Zanabazar_Square",
+    "Zanb"
+  ]
+}
+Array.prototype.push.apply(data.$LONE, data.General_Category)
+data.gc = data.General_Category
+data.sc = data.Script_Extensions = data.scx = data.Script
+
+export default data
diff --git a/tools/tests/apps/modules/imports/links/acorn/src/util.js b/tools/tests/apps/modules/imports/links/acorn/src/util.js
new file mode 100644
index 0000000000..9f548a140e
--- /dev/null
+++ b/tools/tests/apps/modules/imports/links/acorn/src/util.js
@@ -0,0 +1,11 @@
+const {hasOwnProperty, toString} = Object.prototype
+
+// Checks if an object has a property.
+
+export function has(obj, propName) {
+  return hasOwnProperty.call(obj, propName)
+}
+
+export const isArray = Array.isArray || ((obj) => (
+  toString.call(obj) === "[object Array]"
+))
diff --git a/tools/tests/apps/modules/imports/links/acorn/src/walk/index.js b/tools/tests/apps/modules/imports/links/acorn/src/walk/index.js
new file mode 100644
index 0000000000..fdc776c8dc
--- /dev/null
+++ b/tools/tests/apps/modules/imports/links/acorn/src/walk/index.js
@@ -0,0 +1,370 @@
+// AST walker module for Mozilla Parser API compatible trees
+
+// A simple walk is one where you simply specify callbacks to be
+// called on specific nodes. The last two arguments are optional. A
+// simple use would be
+//
+//     walk.simple(myTree, {
+//         Expression: function(node) { ... }
+//     });
+//
+// to do something with all expressions. All Parser API node types
+// can be used to identify node types, as well as Expression,
+// Statement, and ScopeBody, which denote categories of nodes.
+//
+// The base argument can be used to pass a custom (recursive)
+// walker, and state can be used to give this walked an initial
+// state.
+
+export function simple(node, visitors, baseVisitor = base, state, override) {
+  (function c(node, st, override) {
+    let type = override || node.type, found = visitors[type]
+    baseVisitor[type](node, st, c)
+    if (found) found(node, st)
+  })(node, state, override)
+}
+
+// An ancestor walk keeps an array of ancestor nodes (including the
+// current node) and passes them to the callback as third parameter
+// (and also as state parameter when no other state is present).
+export function ancestor(node, visitors, baseVisitor = base, state) {
+  let ancestors = []
+  ;(function c(node, st, override) {
+    let type = override || node.type, found = visitors[type]
+    let isNew = node != ancestors[ancestors.length - 1]
+    if (isNew) ancestors.push(node)
+    baseVisitor[type](node, st, c)
+    if (found) found(node, st || ancestors, ancestors)
+    if (isNew) ancestors.pop()
+  })(node, state)
+}
+
+// A recursive walk is one where your functions override the default
+// walkers. They can modify and replace the state parameter that's
+// threaded through the walk, and can opt how and whether to walk
+// their child nodes (by calling their third argument on these
+// nodes).
+export function recursive(node, state, funcs, baseVisitor, override) {
+  let visitor = funcs ? exports.make(funcs, baseVisitor) : baseVisitor
+  ;(function c(node, st, override) {
+    visitor[override || node.type](node, st, c)
+  })(node, state, override)
+}
+
+function makeTest(test) {
+  if (typeof test == "string")
+    return type => type == test
+  else if (!test)
+    return () => true
+  else
+    return test
+}
+
+class Found {
+  constructor(node, state) { this.node = node; this.state = state }
+}
+
+// A full walk triggers the callback on each node
+export function full(node, callback, baseVisitor = base, state, override) {
+  (function c(node, st, override) {
+    let type = override || node.type
+    baseVisitor[type](node, st, c)
+    if (!override) callback(node, st, type)
+  })(node, state, override)
+}
+
+// An fullAncestor walk is like an ancestor walk, but triggers
+// the callback on each node
+export function fullAncestor(node, callback, baseVisitor = base, state) {
+  let ancestors = []
+  ;(function c(node, st, override) {
+    let type = override || node.type
+    let isNew = node != ancestors[ancestors.length - 1]
+    if (isNew) ancestors.push(node)
+    baseVisitor[type](node, st, c)
+    if (!override) callback(node, st || ancestors, ancestors, type)
+    if (isNew) ancestors.pop()
+  })(node, state)
+}
+
+// Find a node with a given start, end, and type (all are optional,
+// null can be used as wildcard). Returns a {node, state} object, or
+// undefined when it doesn't find a matching node.
+export function findNodeAt(node, start, end, test, baseVisitor = base, state) {
+  test = makeTest(test)
+  try {
+    (function c(node, st, override) {
+      let type = override || node.type
+      if ((start == null || node.start <= start) &&
+          (end == null || node.end >= end))
+        baseVisitor[type](node, st, c)
+      if ((start == null || node.start == start) &&
+          (end == null || node.end == end) &&
+          test(type, node))
+        throw new Found(node, st)
+    })(node, state)
+  } catch (e) {
+    if (e instanceof Found) return e
+    throw e
+  }
+}
+
+// Find the innermost node of a given type that contains the given
+// position. Interface similar to findNodeAt.
+export function findNodeAround(node, pos, test, baseVisitor = base, state) {
+  test = makeTest(test)
+  try {
+    (function c(node, st, override) {
+      let type = override || node.type
+      if (node.start > pos || node.end < pos) return
+      baseVisitor[type](node, st, c)
+      if (test(type, node)) throw new Found(node, st)
+    })(node, state)
+  } catch (e) {
+    if (e instanceof Found) return e
+    throw e
+  }
+}
+
+// Find the outermost matching node after a given position.
+export function findNodeAfter(node, pos, test, baseVisitor = base, state) {
+  test = makeTest(test)
+  try {
+    (function c(node, st, override) {
+      if (node.end < pos) return
+      let type = override || node.type
+      if (node.start >= pos && test(type, node)) throw new Found(node, st)
+      baseVisitor[type](node, st, c)
+    })(node, state)
+  } catch (e) {
+    if (e instanceof Found) return e
+    throw e
+  }
+}
+
+// Find the outermost matching node before a given position.
+export function findNodeBefore(node, pos, test, baseVisitor = base, state) {
+  test = makeTest(test)
+  let max
+  ;(function c(node, st, override) {
+    if (node.start > pos) return
+    let type = override || node.type
+    if (node.end <= pos && (!max || max.node.end < node.end) && test(type, node))
+      max = new Found(node, st)
+    baseVisitor[type](node, st, c)
+  })(node, state)
+  return max
+}
+
+// Fallback to an Object.create polyfill for older environments.
+const create = Object.create || function(proto) {
+  function Ctor() {}
+  Ctor.prototype = proto
+  return new Ctor
+}
+
+// Used to create a custom walker. Will fill in all missing node
+// type properties with the defaults.
+export function make(funcs, baseVisitor = base) {
+  let visitor = create(baseVisitor)
+  for (let type in funcs) visitor[type] = funcs[type]
+  return visitor
+}
+
+function skipThrough(node, st, c) { c(node, st) }
+function ignore(_node, _st, _c) {}
+
+// Node walkers.
+
+export const base = {}
+
+base.Program = base.BlockStatement = (node, st, c) => {
+  for (let stmt of node.body)
+    c(stmt, st, "Statement")
+}
+base.Statement = skipThrough
+base.EmptyStatement = ignore
+base.ExpressionStatement = base.ParenthesizedExpression =
+  (node, st, c) => c(node.expression, st, "Expression")
+base.IfStatement = (node, st, c) => {
+  c(node.test, st, "Expression")
+  c(node.consequent, st, "Statement")
+  if (node.alternate) c(node.alternate, st, "Statement")
+}
+base.LabeledStatement = (node, st, c) => c(node.body, st, "Statement")
+base.BreakStatement = base.ContinueStatement = ignore
+base.WithStatement = (node, st, c) => {
+  c(node.object, st, "Expression")
+  c(node.body, st, "Statement")
+}
+base.SwitchStatement = (node, st, c) => {
+  c(node.discriminant, st, "Expression")
+  for (let cs of node.cases) {
+    if (cs.test) c(cs.test, st, "Expression")
+    for (let cons of cs.consequent)
+      c(cons, st, "Statement")
+  }
+}
+base.SwitchCase = (node, st, c) => {
+  if (node.test) c(node.test, st, "Expression")
+  for (let cons of node.consequent)
+    c(cons, st, "Statement")
+}
+base.ReturnStatement = base.YieldExpression = base.AwaitExpression = (node, st, c) => {
+  if (node.argument) c(node.argument, st, "Expression")
+}
+base.ThrowStatement = base.SpreadElement =
+  (node, st, c) => c(node.argument, st, "Expression")
+base.TryStatement = (node, st, c) => {
+  c(node.block, st, "Statement")
+  if (node.handler) c(node.handler, st)
+  if (node.finalizer) c(node.finalizer, st, "Statement")
+}
+base.CatchClause = (node, st, c) => {
+  c(node.param, st, "Pattern")
+  c(node.body, st, "ScopeBody")
+}
+base.WhileStatement = base.DoWhileStatement = (node, st, c) => {
+  c(node.test, st, "Expression")
+  c(node.body, st, "Statement")
+}
+base.ForStatement = (node, st, c) => {
+  if (node.init) c(node.init, st, "ForInit")
+  if (node.test) c(node.test, st, "Expression")
+  if (node.update) c(node.update, st, "Expression")
+  c(node.body, st, "Statement")
+}
+base.ForInStatement = base.ForOfStatement = (node, st, c) => {
+  c(node.left, st, "ForInit")
+  c(node.right, st, "Expression")
+  c(node.body, st, "Statement")
+}
+base.ForInit = (node, st, c) => {
+  if (node.type == "VariableDeclaration") c(node, st)
+  else c(node, st, "Expression")
+}
+base.DebuggerStatement = ignore
+
+base.FunctionDeclaration = (node, st, c) => c(node, st, "Function")
+base.VariableDeclaration = (node, st, c) => {
+  for (let decl of node.declarations)
+    c(decl, st)
+}
+base.VariableDeclarator = (node, st, c) => {
+  c(node.id, st, "Pattern")
+  if (node.init) c(node.init, st, "Expression")
+}
+
+base.Function = (node, st, c) => {
+  if (node.id) c(node.id, st, "Pattern")
+  for (let param of node.params)
+    c(param, st, "Pattern")
+  c(node.body, st, node.expression ? "ScopeExpression" : "ScopeBody")
+}
+// FIXME drop these node types in next major version
+// (They are awkward, and in ES6 every block can be a scope.)
+base.ScopeBody = (node, st, c) => c(node, st, "Statement")
+base.ScopeExpression = (node, st, c) => c(node, st, "Expression")
+
+base.Pattern = (node, st, c) => {
+  if (node.type == "Identifier")
+    c(node, st, "VariablePattern")
+  else if (node.type == "MemberExpression")
+    c(node, st, "MemberPattern")
+  else
+    c(node, st)
+}
+base.VariablePattern = ignore
+base.MemberPattern = skipThrough
+base.RestElement = (node, st, c) => c(node.argument, st, "Pattern")
+base.ArrayPattern = (node, st, c) => {
+  for (let elt of node.elements) {
+    if (elt) c(elt, st, "Pattern")
+  }
+}
+base.ObjectPattern = (node, st, c) => {
+  for (let prop of node.properties) {
+    if (prop.type === "Property") {
+      if (prop.computed) c(prop.key, st, "Expression")
+      c(prop.value, st, "Pattern")
+    } else if (prop.type === "RestElement") {
+      c(prop.argument, st, "Pattern")
+    }
+  }
+}
+
+base.Expression = skipThrough
+base.ThisExpression = base.Super = base.MetaProperty = ignore
+base.ArrayExpression = (node, st, c) => {
+  for (let elt of node.elements) {
+    if (elt) c(elt, st, "Expression")
+  }
+}
+base.ObjectExpression = (node, st, c) => {
+  for (let prop of node.properties)
+    c(prop, st)
+}
+base.FunctionExpression = base.ArrowFunctionExpression = base.FunctionDeclaration
+base.SequenceExpression = base.TemplateLiteral = (node, st, c) => {
+  for (let expr of node.expressions)
+    c(expr, st, "Expression")
+}
+base.UnaryExpression = base.UpdateExpression = (node, st, c) => {
+  c(node.argument, st, "Expression")
+}
+base.BinaryExpression = base.LogicalExpression = (node, st, c) => {
+  c(node.left, st, "Expression")
+  c(node.right, st, "Expression")
+}
+base.AssignmentExpression = base.AssignmentPattern = (node, st, c) => {
+  c(node.left, st, "Pattern")
+  c(node.right, st, "Expression")
+}
+base.ConditionalExpression = (node, st, c) => {
+  c(node.test, st, "Expression")
+  c(node.consequent, st, "Expression")
+  c(node.alternate, st, "Expression")
+}
+base.NewExpression = base.CallExpression = (node, st, c) => {
+  c(node.callee, st, "Expression")
+  if (node.arguments)
+    for (let arg of node.arguments)
+      c(arg, st, "Expression")
+}
+base.MemberExpression = (node, st, c) => {
+  c(node.object, st, "Expression")
+  if (node.computed) c(node.property, st, "Expression")
+}
+base.ExportNamedDeclaration = base.ExportDefaultDeclaration = (node, st, c) => {
+  if (node.declaration)
+    c(node.declaration, st, node.type == "ExportNamedDeclaration" || node.declaration.id ? "Statement" : "Expression")
+  if (node.source) c(node.source, st, "Expression")
+}
+base.ExportAllDeclaration = (node, st, c) => {
+  c(node.source, st, "Expression")
+}
+base.ImportDeclaration = (node, st, c) => {
+  for (let spec of node.specifiers)
+    c(spec, st)
+  c(node.source, st, "Expression")
+}
+base.ImportSpecifier = base.ImportDefaultSpecifier = base.ImportNamespaceSpecifier = base.Identifier = base.Literal = ignore
+
+base.TaggedTemplateExpression = (node, st, c) => {
+  c(node.tag, st, "Expression")
+  c(node.quasi, st, "Expression")
+}
+base.ClassDeclaration = base.ClassExpression = (node, st, c) => c(node, st, "Class")
+base.Class = (node, st, c) => {
+  if (node.id) c(node.id, st, "Pattern")
+  if (node.superClass) c(node.superClass, st, "Expression")
+  c(node.body, st)
+}
+base.ClassBody = (node, st, c) => {
+  for (let elt of node.body)
+    c(elt, st)
+}
+base.MethodDefinition = base.Property = (node, st, c) => {
+  if (node.computed) c(node.key, st, "Expression")
+  c(node.value, st, "Expression")
+}
diff --git a/tools/tests/apps/modules/imports/links/acorn/src/whitespace.js b/tools/tests/apps/modules/imports/links/acorn/src/whitespace.js
new file mode 100644
index 0000000000..094c2e4a47
--- /dev/null
+++ b/tools/tests/apps/modules/imports/links/acorn/src/whitespace.js
@@ -0,0 +1,13 @@
+// Matches a whole line break (where CRLF is considered a single
+// line break). Used to count lines.
+
+export const lineBreak = /\r\n?|\n|\u2028|\u2029/
+export const lineBreakG = new RegExp(lineBreak.source, "g")
+
+export function isNewLine(code) {
+  return code === 10 || code === 13 || code === 0x2028 || code === 0x2029
+}
+
+export const nonASCIIwhitespace = /[\u1680\u180e\u2000-\u200a\u202f\u205f\u3000\ufeff]/
+
+export const skipWhiteSpace = /(?:\s|\/\/.*|\/\*[^]*?\*\/)*/g
diff --git a/tools/tests/apps/modules/imports/links/immutable-tuple b/tools/tests/apps/modules/imports/links/immutable-tuple
new file mode 120000
index 0000000000..0814a6ac4e
--- /dev/null
+++ b/tools/tests/apps/modules/imports/links/immutable-tuple
@@ -0,0 +1 @@
+../../node_modules/immutable-tuple
\ No newline at end of file
diff --git a/tools/tests/apps/modules/imports/links/lodash-es b/tools/tests/apps/modules/imports/links/lodash-es
new file mode 120000
index 0000000000..42a542a26b
--- /dev/null
+++ b/tools/tests/apps/modules/imports/links/lodash-es
@@ -0,0 +1 @@
+../../node_modules/lodash-es
\ No newline at end of file
diff --git a/tools/tests/apps/modules/package-lock.json b/tools/tests/apps/modules/package-lock.json
index 250f992df7..677a753fda 100644
--- a/tools/tests/apps/modules/package-lock.json
+++ b/tools/tests/apps/modules/package-lock.json
@@ -160,6 +160,9 @@
         "to-fast-properties": "2.0.0"
       }
     },
+    "acorn": {
+      "version": "file:imports/links/acorn"
+    },
     "ansi-styles": {
       "version": "3.2.1",
       "resolved": "https://registry.npmjs.org/ansi-styles/-/ansi-styles-3.2.1.tgz",
@@ -503,6 +506,11 @@
       "resolved": "https://registry.npmjs.org/ieee754/-/ieee754-1.1.8.tgz",
       "integrity": "sha1-vjPUCsEO8ZJnAfbwii2G+/0a0+Q="
     },
+    "immutable-tuple": {
+      "version": "0.4.4",
+      "resolved": "https://registry.npmjs.org/immutable-tuple/-/immutable-tuple-0.4.4.tgz",
+      "integrity": "sha512-nJQ1HbFPgCLHMsO3Y9f55hV9z7RSloQF3PkkmKF70OxvgPT6Tz+EgY+4k64LusutkmOOlM9FGDwz2ow3CDvZCA=="
+    },
     "inherits": {
       "version": "2.0.3",
       "resolved": "https://registry.npmjs.org/inherits/-/inherits-2.0.3.tgz",
@@ -621,6 +629,11 @@
       "resolved": "https://registry.npmjs.org/lodash/-/lodash-4.17.5.tgz",
       "integrity": "sha512-svL3uiZf1RwhH+cWrfZn3A4+U58wbP0tGVTLQPbjplZxZ8ROD9VLuNgsRniTlLe7OlSqR79RUehXgpBW/s0IQw=="
     },
+    "lodash-es": {
+      "version": "4.17.7",
+      "resolved": "https://registry.npmjs.org/lodash-es/-/lodash-es-4.17.7.tgz",
+      "integrity": "sha512-jzqTi3vk4J5Dxq43cNjB0ekfCjPLHixoY2Sc0WHTo+0r928taLqe/VCt02vY5uQBvg0rdXgL3xWkK4X0MCmZcw=="
+    },
     "lodash.isplainobject": {
       "version": "4.0.6",
       "resolved": "https://registry.npmjs.org/lodash.isplainobject/-/lodash.isplainobject-4.0.6.tgz",
diff --git a/tools/tests/apps/modules/package.json b/tools/tests/apps/modules/package.json
index ad2bee638a..5b73b6b8ae 100644
--- a/tools/tests/apps/modules/package.json
+++ b/tools/tests/apps/modules/package.json
@@ -7,11 +7,14 @@
     "@babel/core": "^7.0.0-beta.40",
     "@babel/plugin-proposal-optional-chaining": "^7.0.0-beta.40",
     "@babel/runtime": "^7.0.0-beta.42",
+    "acorn": "file:imports/links/acorn",
     "aws-sdk": "^2.2.41",
     "babel-plugin-transform-do-expressions": "^6.22.0",
     "cli-color": "^0.2.3",
     "github": "^0.2.4",
     "idle-gc": "^1.0.1",
+    "immutable-tuple": "^0.4.4",
+    "lodash-es": "^4.17.7",
     "meteor-node-stubs": "^0.3.2",
     "moment": "2.11.1",
     "mssql": "^3.1.1",
diff --git a/tools/tests/apps/modules/tests.js b/tools/tests/apps/modules/tests.js
index e4fec9ec2f..da7464e677 100644
--- a/tools/tests/apps/modules/tests.js
+++ b/tools/tests/apps/modules/tests.js
@@ -460,6 +460,44 @@ describe("Meteor packages", () => {
   });
 });
 
+describe("symlinking node_modules", () => {
+  it("should allow selective compilation of npm packages", () => {
+    import each from "lodash-es/each";
+    import range from "lodash-es/range";
+    const n = 100;
+    let sum = 0;
+    each(range(1, n + 1), n => sum += n);
+    assert.strictEqual(sum, n * (n + 1) / 2);
+  });
+
+  it("should preserve equivalence for require", async () => {
+    const pkg1 = require("immutable-tuple/package.json");
+    const pkg2 = require("./imports/links/immutable-tuple/package");
+    assert.strictEqual(pkg1.author.name, "Ben Newman");
+    assert.strictEqual(pkg1.author, pkg2.author);
+  });
+
+  it("should preserve equivalence for dynamic import()", async () => {
+    const { default: tuple1 } = await import("immutable-tuple/src/tuple");
+    const { tuple: tuple2 } =
+      await import("/imports/links/immutable-tuple/src/tuple");
+    assert.strictEqual(tuple1, tuple2);
+  });
+
+  it("should support application-compiled `npm link`ed packages", () => {
+    assert.strictEqual(
+      require.resolve("acorn"),
+      "/node_modules/acorn/src/index.js"
+    );
+    const { parse } = require("acorn");
+    assert.strictEqual(typeof parse, "function");
+    assert.strictEqual(
+      parse,
+      require("./imports/links/acorn").parse
+    );
+  });
+});
+
 describe("ecmascript miscellany", () => {
   it("JSX should work in .js files on both client and server", () => {
     const React = {

From 602dffb8b1d51c52f0dbb7ea54c9c96adbf4bf9d Mon Sep 17 00:00:00 2001
From: Ben Newman <ben@meteor.com>
Date: Mon, 26 Mar 2018 18:02:52 -0400
Subject: [PATCH 10/12] Mention selective compilation of npm packages in
 History.md.

---
 History.md | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/History.md b/History.md
index 45aecaf1b6..4e085f36d3 100644
--- a/History.md
+++ b/History.md
@@ -1,5 +1,14 @@
 ## v.NEXT
 
+* Although Meteor does not recompile packages installed in `node_modules`
+  by default, npm package code can now be selectively compiled by creating
+  symbolic links to those packages within your application, outside of
+  `node_modules`. Meteor will compile the exposed code as if it was part
+  of your application, using whatever compiler plugins you have installed,
+  and also guarantee that you get the compiled code when you import from
+  `node_modules`. [PR #9771](https://github.com/meteor/meteor/pull/9771)
+  [Feature #6](https://github.com/meteor/meteor-feature-requests/issues/6)
+
 * Applications may now specify client and server entry point modules in a
   newly-supported `"meteor"` section of `package.json`:
   ```js

From e24dadca54891b2478e6baa1792f0f58c2bbc5cd Mon Sep 17 00:00:00 2001
From: Ben Newman <ben@meteor.com>
Date: Tue, 27 Mar 2018 10:10:23 -0400
Subject: [PATCH 11/12] Expand History.md entry about selective node_modules
 compilation.

---
 History.md | 47 +++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 41 insertions(+), 6 deletions(-)

diff --git a/History.md b/History.md
index 4e085f36d3..c1eef719d0 100644
--- a/History.md
+++ b/History.md
@@ -1,12 +1,47 @@
 ## v.NEXT
 
 * Although Meteor does not recompile packages installed in `node_modules`
-  by default, npm package code can now be selectively compiled by creating
-  symbolic links to those packages within your application, outside of
-  `node_modules`. Meteor will compile the exposed code as if it was part
-  of your application, using whatever compiler plugins you have installed,
-  and also guarantee that you get the compiled code when you import from
-  `node_modules`. [PR #9771](https://github.com/meteor/meteor/pull/9771)
+  by default, compilation of specific npm packages (for example, to
+  support older browsers that the package author neglected) can now be
+  enabled in one of two ways:
+
+  * Clone the package repository into your application's `imports`
+    directory, make any modifications necessary, then run
+    ```sh
+    meteor npm install imports/the-package
+    ```
+    to link `the-package` into `node_modules`. Meteor will compile the
+    contents of the package exposed via `imports/the-package`, and this
+    compiled code will be used when you import `the-package` in any of the
+    usual ways:
+    ```js
+    import stuff from "the-package"
+    require("the-package") === require("/imports/the-package")
+    import("the-package").then(...)
+    ```
+    This reuse of compiled code is the critical new feature that was added
+    in Meteor 1.6.2.
+
+  * Install the package normally with `meteor npm install the-package`,
+    then create a symbolic link *to* the installed package elsewhere in
+    your application, outside of `node_modules`:
+    ```sh
+    meteor npm install the-package
+    cd imports
+    ln -s ../node_modules/the-package .
+    ```
+    Again, Meteor will compile the contents of the package because they
+    are exposed outside of `node_modules`, and the compiled code will be
+    used whenever `the-package` is imported from `node_modules`.
+
+    > Note: this technique also works if you create symbolic links to
+      individual files, rather than linking the entire package directory.
+
+  In both cases, Meteor will compile the exposed code as if it was part of
+  your application, using whatever compiler plugins you have installed.
+  You can influence this compilation using `.babelrc` files or any other
+  techniques you would normally use to configure compilation of
+  application code. [PR #9771](https://github.com/meteor/meteor/pull/9771)
   [Feature #6](https://github.com/meteor/meteor-feature-requests/issues/6)
 
 * Applications may now specify client and server entry point modules in a

From 61226bc2992a34e9a89beaa9e11790a5af41acf7 Mon Sep 17 00:00:00 2001
From: Ben Newman <ben@meteor.com>
Date: Tue, 27 Mar 2018 10:16:10 -0400
Subject: [PATCH 12/12] Reword to avoid implying that `meteor npm install ...`
 is special.

---
 History.md | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/History.md b/History.md
index c1eef719d0..f6de08445e 100644
--- a/History.md
+++ b/History.md
@@ -6,14 +6,14 @@
   enabled in one of two ways:
 
   * Clone the package repository into your application's `imports`
-    directory, make any modifications necessary, then run
+    directory, make any modifications necessary, then use `npm install` to
+    link `the-package` into `node_modules`:
     ```sh
     meteor npm install imports/the-package
     ```
-    to link `the-package` into `node_modules`. Meteor will compile the
-    contents of the package exposed via `imports/the-package`, and this
-    compiled code will be used when you import `the-package` in any of the
-    usual ways:
+    Meteor will compile the contents of the package exposed via
+    `imports/the-package`, and this compiled code will be used when you
+    import `the-package` in any of the usual ways:
     ```js
     import stuff from "the-package"
     require("the-package") === require("/imports/the-package")