fix(Promise): Make sure we check for native Promise before es6-promise gets a chance to polyfill

vicb · vicb · commit fa18d4c4934b · 2015-12-11T11:43:18.000-08:00
diff --git a/lib/microtask.js b/lib/microtask.js
@@ -1,7 +1,35 @@
 'use strict';
 
+// TODO(vicb): Create a benchmark for the different methods & the usage of the queue
+// see https://github.com/angular/zone.js/issues/97
+
+// It is required to initialize hasNativePromise before requiring es6-promise otherwise es6-promise would
+// overwrite the native Promise implementation on v8 and the check would always return false.
+// see https://github.com/jakearchibald/es6-promise/issues/140
+var hasNativePromise = typeof Promise !== "undefined" &&
+    Promise.toString().indexOf("[native code]") !== -1;
+
+var isFirefox = global.navigator &&
+    global.navigator.userAgent.toLowerCase().indexOf('firefox') > -1;
+
+var resolvedPromise;
+
+// TODO(vicb): remove '!isFirefox' when the bug gets fixed:
+// https://bugzilla.mozilla.org/show_bug.cgi?id=1162013
+if (hasNativePromise && !isFirefox) {
+  // When available use a native Promise to schedule microtasks.
+  // When not available, es6-promise fallback will be used
+  resolvedPromise = Promise.resolve();
+}
+
 var es6Promise = require('es6-promise').Promise;
 
+if (resolvedPromise) {
+  es6Promise._setScheduler(function(fn) {
+    resolvedPromise.then(fn);
+  });
+}
+
 // es6-promise asap should schedule microtasks via zone.scheduleMicrotask so that any
 // user defined hooks are triggered
 es6Promise._setAsap(function(fn, arg) {
@@ -25,23 +53,5 @@ module.exports = {
   addMicrotaskSupport: addMicrotaskSupport
 };
 
-// TODO(vicb): Create a benchmark for the different methods & the usage of the queue
-// see https://github.com/angular/zone.js/issues/97
 
-var hasNativePromise = typeof Promise !== "undefined" &&
-                       Promise.toString().indexOf("[native code]") !== -1;
-
-var isFirefox = global.navigator &&
-                global.navigator.userAgent.toLowerCase().indexOf('firefox') > -1;
-
-// TODO(vicb): remove '!isFirefox' when the bug gets fixed:
-// https://bugzilla.mozilla.org/show_bug.cgi?id=1162013
-if (hasNativePromise && !isFirefox) {
-  // When available use a native Promise to schedule microtasks.
-  // When not available, es6-promise fallback will be used
-  var resolvedPromise = Promise.resolve();
-  es6Promise._setScheduler(function(fn) {
-    resolvedPromise.then(fn);
-  });
-}
 
