Decide laziness when resources are added.

This used to happen when we ran the ImportScanner, but the earlier we can
make this decision the better.

tools/isobuild/compiler-plugin.js

@@ -372,6 +372,31 @@ class ResourceSlot {
     return fileOptions && fileOptions[name];
   }
 
+  _isLazy(options) {
+    let lazy = this._getOption("lazy", options);
+
+    if (typeof lazy === "boolean") {
+      return lazy;
+    }
+
+    const sourcePath = this.inputResource.path;
+
+    if (sourcePath.endsWith(".json")) {
+      // JSON files have no side effects, so there is no reason for them
+      // ever to be evaluated eagerly.
+      return true;
+    }
+
+    // If file.lazy was not previously defined, mark the file lazy if it
+    // is contained by an imports directory. Note that any files contained
+    // by a node_modules directory will already have been marked lazy in
+    // PackageSource#_inferFileOptions.
+    return this.packageSourceBatch.useMeteorInstall &&
+      files.pathDirname(sourcePath)
+        .split(files.pathSep)
+        .indexOf("imports") >= 0;
+  }
+
   addStylesheet(options) {
     const self = this;
     if (! self.sourceProcessor) {
@@ -387,7 +412,7 @@ class ResourceSlot {
       // XXX do we need to call convertSourceMapPaths here like we did
       //     in legacy handlers?
       sourceMap: options.sourceMap,
-      lazy: self._getOption("lazy", options),
+      lazy: self._isLazy(options),
     });
   }
 
@@ -415,7 +440,7 @@ class ResourceSlot {
       sourceMap: options.sourceMap,
       // intentionally preserve a possible `undefined` value for files
       // in apps, rather than convert it into `false` via `!!`
-      lazy: self._getOption("lazy", options),
+      lazy: self._isLazy(options),
       bare: !! self._getOption("bare", options),
       mainModule: !! self._getOption("mainModule", options),
     });
@@ -442,7 +467,7 @@ class ResourceSlot {
       servePath: self.packageSourceBatch.unibuild.pkg._getServePath(
         options.path),
       hash: sha1(options.data),
-      lazy: self._getOption("lazy", options),
+      lazy: self._isLazy(options),
     });
   }
 
@@ -464,7 +489,7 @@ class ResourceSlot {
     self.outputResources.push({
       type: options.section,
       data: new Buffer(files.convertToStandardLineEndings(options.data), 'utf8'),
-      lazy: self._getOption("lazy", options),
+      lazy: self._isLazy(options),
     });
   }
 }

tools/isobuild/import-scanner.js

@@ -54,11 +54,8 @@ export default class ImportScanner {
       const absPath = pathJoin(this.sourceRoot, file.sourcePath);
 
       // Files that are not eagerly evaluated (lazy) will only be included
-      // in the bundle if they are actually imported.
-      file.lazy = this._isFileLazy(file);
-
-      // Files that are eagerly evaluated are effectively "imported" as
-      // entry points.
+      // in the bundle if they are actually imported. Files that are
+      // eagerly evaluated are effectively "imported" as entry points.
       file.imported = ! file.lazy;
 
       file.installPath = this._getInstallPath(absPath);
@@ -106,30 +103,6 @@ export default class ImportScanner {
     return this.outputFiles;
   }
 
-  _isFileLazy(file) {
-    if (typeof file.lazy === "boolean") {
-      return file.lazy;
-    }
-
-    if (file.sourcePath.endsWith(".json")) {
-      // JSON files have no side effects, so there is no reason for them
-      // ever to be evaluated eagerly.
-      return true;
-    }
-
-    // If file.lazy was not previously defined, mark the file lazy if it
-    // is contained by an imports directory. Note that any files contained
-    // by a node_modules directory will already have been marked lazy in
-    // PackageSource#_inferFileOptions. The reason we can't do all our
-    // lazy marking in the _inferFileOptions method is that we don't know
-    // then whether the current app or package is using the modules
-    // package. At this point, we know the modules package must be in use,
-    // because the ImportScanner is only ever used when modules are used.
-    return this._splitPath(
-      pathDirname(file.sourcePath)
-    ).indexOf("imports") >= 0;
-  }
-
   _scanFile(file) {
     const absPath = pathJoin(this.sourceRoot, file.sourcePath);
     file.deps = file.deps || keys(