From be68fb8d2f9cbbd484b1f32cd135aa8820b3c15d Mon Sep 17 00:00:00 2001
From: Ben Newman <ben@meteor.com>
Date: Sat, 4 Mar 2017 13:08:58 -0500
Subject: [PATCH] Call this.unblock() in __dynamicImport method.

This prevents __dynamicImport from blocking other method calls made by the
application, but introduces the possibility that __dynamicImport method
results could be delivered out of order, which is now handled in the
fetchMissing function.
---
 packages/dynamic-import/client.js | 25 +++++++++++++++++++++++--
 packages/dynamic-import/server.js |  1 +
 2 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/packages/dynamic-import/client.js b/packages/dynamic-import/client.js
index 647bdfee94..b6282fb6c4 100644
--- a/packages/dynamic-import/client.js
+++ b/packages/dynamic-import/client.js
@@ -58,13 +58,34 @@ Module.prototype.dynamicImport = function (id) {
   });
 };
 
+// Results from fetchMissing must be delivered in the same order as calls
+// to fetchMissing, because previous results may include modules needed by
+// more recent calls. In practice, results are usually delivered in order,
+// but might be delivered out of order because the __dynamicImport method
+// calls this.unblock(). To achieve this ordering of results while still
+// allowing parallel __dynamicImport method calls, we keep track of the
+// most recent Promise returned by fetchMissing, and delay resolving the
+// next Promise until the previous Promise has been resolved or rejected.
+var lastFetchMissingPromise = delayPromise;
+
 function fetchMissing(missingTree) {
-  return new Promise(function (resolve, reject) {
+  // Save the Promise that was most recent when fetchMissing was called.
+  var previousPromise = lastFetchMissingPromise;
+
+  // Update lastFetchMissingPromise immediately, without waiting for
+  // the results to be delivered.
+  return lastFetchMissingPromise = new Promise(function (resolve, reject) {
     Meteor.call(
       "__dynamicImport",
       missingTree,
       function (error, resultsTree) {
-        error ? reject(error) : resolve(resultsTree);
+        if (error) {
+          reject(error);
+        } else {
+          resolve = resolve.bind(null, resultsTree)
+          // Continue even if previousPromise was rejected.
+          previousPromise.then(resolve, resolve);
+        }
       }
     );
   }).then(installResults);
diff --git a/packages/dynamic-import/server.js b/packages/dynamic-import/server.js
index 569591f202..7f4ed98b9a 100644
--- a/packages/dynamic-import/server.js
+++ b/packages/dynamic-import/server.js
@@ -22,6 +22,7 @@ Object.keys(dynamicImportInfo).forEach(platform => {
 Meteor.methods({
   __dynamicImport(tree) {
     check(tree, Object);
+    this.unblock();
 
     const platform = this.connection ? "web.browser" : "server";
     const pathParts = [];