Merge pull request #16282 from emberjs/fix-nested-observerset-flushes

[BUGFIX beta] Fix nested ObserverSet flushes

Author: rwjblue

packages/ember-metal/lib/observer_set.js

@@ -1,3 +1,5 @@
+import { sendEvent } from './events';
+
 /**
   ObserverSet is a data structure used to keep track of observers
   that have been deferred.
@@ -27,25 +29,27 @@ export default class ObserverSet {
     }
 
     if (!keys.has(key)) {
-      this.queue.push({ object, key });
+      this.queue.push([object, key]);
       keys.add(key);
     }
   }
 
-  forEach(cb) {
-    for (let i = 0; i < this.queue.length; i++) {
-      let { object, key } = this.queue[i];
+  flush() {
+    // The queue is saved off to support nested flushes.
+    let queue = this.queue;
+    this.added.clear();
+    this.queue = [];
+
+    for (let i = 0; i < queue.length; i++) {
+      let pair = queue[i];
+      let object = pair[0];
+      let key = pair[1];
 
       if (object.isDestroying || object.isDestroyed) {
         continue;
       }
 
-      cb(object, key);
+      sendEvent(object, key, pair);
     }
   }
-
-  clear() {
-    this.added.clear();
-    this.queue.length = 0;
-  }
 }

packages/ember-metal/lib/property_events.js

@@ -188,8 +188,7 @@ function beginPropertyChanges() {
 function endPropertyChanges() {
   deferred--;
   if (deferred <= 0) {
-    observerSet.forEach((object, key)=> sendEvent(object, key, [object, key]));
-    observerSet.clear();
+    observerSet.flush();
   }
 }
 

packages/ember-metal/tests/observer_test.js

@@ -673,6 +673,21 @@ testBoth('observers added/removed during changeProperties should do the right th
   assert.equal(removedAfterLastChangeObserver.didChangeCount, 0, 'removeObserver called after the last change sees none');
 });
 
+testBoth('calling changeProperties while executing deferred observers works correctly', function(get, set, assert) {
+  let obj = { foo: 0 };
+  let fooDidChange = 0;
+  
+  addObserver(obj, 'foo', () => {
+    fooDidChange++;
+    changeProperties(() => {});
+  });
+  
+  changeProperties(() => {
+    set(obj, 'foo', 1);
+  });
+  
+  assert.equal(fooDidChange, 1);
+});
 
 QUnit.module('Keys behavior with observers');