[BUGFIX release] Fix issue #14672

packages/ember-metal/lib/alias.js

@@ -14,6 +14,8 @@ import {
   removeDependentKeys
 } from './dependent_keys';
 
+const CONSUMED = {};
+
 export default function alias(altKey) {
   return new AliasedProperty(altKey);
 }
@@ -34,28 +36,30 @@ AliasedProperty.prototype.setup = function(obj, keyName) {
   }
 };
 
-AliasedProperty.prototype._addDependentKeyIfMissing = function(obj, keyName) {
+AliasedProperty.prototype.teardown = function(obj, keyName) {
   let meta = metaFor(obj);
-  if (!meta.peekDeps(this.altKey, keyName)) {
-    addDependentKeys(this, obj, keyName, meta);
+  if (meta.peekWatching(keyName)) {
+    removeDependentKeys(this, obj, keyName, meta);
   }
 };
 
-AliasedProperty.prototype._removeDependentKeyIfAdded = function(obj, keyName) {
-  let meta = metaFor(obj);
-  if (meta.peekDeps(this.altKey, keyName)) {
-    removeDependentKeys(this, obj, keyName, meta);
-  }
+AliasedProperty.prototype.willWatch = function(obj, keyName) {
+  addDependentKeys(this, obj, keyName, metaFor(obj));
 };
 
-AliasedProperty.prototype.willWatch = AliasedProperty.prototype._addDependentKeyIfMissing;
-AliasedProperty.prototype.didUnwatch = AliasedProperty.prototype._removeDependentKeyIfAdded;
-AliasedProperty.prototype.teardown = AliasedProperty.prototype._removeDependentKeyIfAdded;
+AliasedProperty.prototype.didUnwatch = function(obj, keyName) {
+  removeDependentKeys(this, obj, keyName, metaFor(obj));
+};
 
 AliasedProperty.prototype.get = function AliasedProperty_get(obj, keyName) {
-  this._addDependentKeyIfMissing(obj, keyName);
-
-  return get(obj, this.altKey);
+  let ret = get(obj, this.altKey);
+  let meta = metaFor(obj);
+  let cache = meta.writableCache();
+  if (cache[keyName] !== CONSUMED) {
+    cache[keyName] = CONSUMED;
+    addDependentKeys(this, obj, keyName, meta);
+  }
+  return ret;
 };
 
 AliasedProperty.prototype.set = function AliasedProperty_set(obj, keyName, value) {

packages/ember-metal/tests/property_did_change_hook.js

@@ -0,0 +1,64 @@
+import { testBoth } from 'internal-test-helpers';
+import { PROPERTY_DID_CHANGE } from '../property_events';
+import { isWatching } from '../watching';
+import { defineProperty } from '../properties';
+import alias from '../alias';
+import { computed } from '../computed';
+
+QUnit.module('PROPERTY_DID_CHANGE');
+
+testBoth('alias and cp', function(get, set) {
+  let counts = {};
+  let obj = {
+    child: {},
+    [PROPERTY_DID_CHANGE](keyName) {
+      counts[keyName] = (counts[keyName] || 0) + 1;
+    }
+  };
+
+  defineProperty(obj, 'cost', alias('child.cost'));
+  defineProperty(obj, 'tax', alias('child.tax'));
+
+  defineProperty(obj, 'total', computed('cost', 'tax', {
+    get() {
+      return get(this, 'cost') + get(this, 'tax');
+    }
+  }));
+
+  ok(!isWatching(obj, 'child.cost'), 'precond alias target `child.cost` is not watched');
+  equal(get(obj, 'cost'), undefined);
+  // this is how PROPERTY_DID_CHANGE will get notified
+  ok(isWatching(obj, 'child.cost'), 'alias target `child.cost` is watched after consumption');
+
+  ok(!isWatching(obj, 'child.tax'), 'precond alias target `child.tax` is not watched');
+  equal(get(obj, 'tax'), undefined);
+  // this is how PROPERTY_DID_CHANGE will get notified
+  ok(isWatching(obj, 'child.tax'), 'alias target `child.cost` is watched after consumption');
+
+  // increments the watching count on the alias itself to 1
+  ok(isNaN(get(obj, 'total')), 'total is initialized');
+
+  // decrements the watching count on the alias itself to 0
+  set(obj, 'child', {
+    cost: 399.00,
+    tax: 32.93
+  });
+
+  // this should have called PROPERTY_DID_CHANGE for all of them
+  equal(counts['cost'], 1,  'PROPERTY_DID_CHANGE called with cost');
+  equal(counts['tax'], 1,   'PROPERTY_DID_CHANGE called with tax');
+  equal(counts['total'], 1, 'PROPERTY_DID_CHANGE called with total');
+
+  // we should still have a dependency installed
+  ok(isWatching(obj, 'child.cost'), 'watching child.cost');
+  ok(isWatching(obj, 'child.tax'), 'watching child.tax');
+
+  set(obj, 'child', {
+    cost: 100.00,
+    tax: 10.00
+  });
+
+  equal(counts['cost'], 2,  'PROPERTY_DID_CHANGE called with cost');
+  equal(counts['tax'], 2,   'PROPERTY_DID_CHANGE called with tax');
+  equal(counts['total'], 1, 'PROPERTY_DID_CHANGE called with total');
+});