Add a failing test for #12475

(cherry picked from commit 7a74435)

packages/ember-metal/lib/watching.js

@@ -53,6 +53,11 @@ export function isWatching(obj, key) {
   return (meta && meta.peekWatching(key)) > 0;
 }
 
+export function watcherCount(obj, key) {
+  var meta = peekMeta(obj);
+  return (meta && meta.peekWatching(key)) || 0;
+}
+
 watch.flushPending = flushPendingChains;
 
 export function unwatch(obj, _keyPath, m) {

packages/ember-runtime/tests/system/array_proxy/watching_and_listening_test.js

@@ -0,0 +1,155 @@
+import { get } from 'ember-metal/property_get';
+import { listenersFor } from 'ember-metal/events';
+import { addObserver } from 'ember-metal/observer';
+import { defineProperty } from 'ember-metal/properties';
+import { watcherCount } from 'ember-metal/watching';
+import computed from 'ember-metal/computed';
+import ArrayProxy from 'ember-runtime/system/array_proxy';
+import { A } from 'ember-runtime/system/native_array';
+
+function sortedListenersFor(obj, eventName) {
+  return listenersFor(obj, eventName).sort((listener1, listener2) => {
+    return (listener1[1] > listener2[1]) ? -1 : 1;
+  });
+}
+
+QUnit.module('ArrayProxy - watching and listening');
+
+QUnit.test(`setting 'content' adds listeners correctly`, function() {
+  let content = A();
+  let proxy = ArrayProxy.create();
+
+  deepEqual(sortedListenersFor(content, '@array:before'), []);
+  deepEqual(sortedListenersFor(content, '@array:change'), []);
+
+  proxy.set('content', content);
+
+  deepEqual(
+    sortedListenersFor(content, '@array:before'),
+    [[proxy, 'contentArrayWillChange'], [proxy, 'arrangedContentArrayWillChange']]
+  );
+  deepEqual(
+    sortedListenersFor(content, '@array:change'),
+    [[proxy, 'contentArrayDidChange'], [proxy, 'arrangedContentArrayDidChange']]
+  );
+});
+
+QUnit.test(`changing 'content' adds and removes listeners correctly`, function() {
+  let content1 = A();
+  let content2 = A();
+  let proxy = ArrayProxy.create({ content: content1 });
+
+  deepEqual(
+    sortedListenersFor(content1, '@array:before'),
+    [[proxy, 'contentArrayWillChange'], [proxy, 'arrangedContentArrayWillChange']]
+  );
+  deepEqual(
+    sortedListenersFor(content1, '@array:change'),
+    [[proxy, 'contentArrayDidChange'], [proxy, 'arrangedContentArrayDidChange']]
+  );
+
+  proxy.set('content', content2);
+
+  deepEqual(sortedListenersFor(content1, '@array:before'), []);
+  deepEqual(sortedListenersFor(content1, '@array:change'), []);
+  deepEqual(
+    sortedListenersFor(content2, '@array:before'),
+    [[proxy, 'contentArrayWillChange'], [proxy, 'arrangedContentArrayWillChange']]
+  );
+  deepEqual(
+    sortedListenersFor(content2, '@array:change'),
+    [[proxy, 'contentArrayDidChange'], [proxy, 'arrangedContentArrayDidChange']]
+  );
+});
+
+QUnit.test(`regression test for https://github.com/emberjs/ember.js/issues/12475`, function() {
+  let item1a = { id: 1 };
+  let item1b = { id: 2 };
+  let item1c = { id: 3 };
+  let content1 = A([item1a, item1b, item1c]);
+
+  let proxy = ArrayProxy.create({ content: content1 });
+  let obj = { proxy };
+
+  defineProperty(obj, 'ids', computed('proxy.@each.id', function() {
+    return get(this, 'proxy').mapBy('id');
+  }));
+
+  // These manually added observers are to simulate the observers added by the
+  // rendering process in a template like:
+  //
+  // {{#each items as |item|}}
+  //   {{item.id}}
+  // {{/each}}
+  addObserver(item1a, 'id', function() { });
+  addObserver(item1b, 'id', function() { });
+  addObserver(item1c, 'id', function() { });
+
+  // The EachProxy has not yet been consumed. Only the manually added
+  // observers are watching.
+  equal(watcherCount(item1a, 'id'), 1);
+  equal(watcherCount(item1b, 'id'), 1);
+  equal(watcherCount(item1c, 'id'), 1);
+
+  // Consume the each proxy. This causes the EachProxy to add two observers
+  // per item: one for "before" events and one for "after" events.
+  deepEqual(get(obj, 'ids'), [1, 2, 3]);
+
+  // For each item, the two each proxy observers and one manual added observer
+  // are watching.
+  equal(watcherCount(item1a, 'id'), 3);
+  equal(watcherCount(item1b, 'id'), 3);
+  equal(watcherCount(item1c, 'id'), 3);
+
+  // This should be a no-op because observers do not fire if the value
+  // 1. is an object and 2. is the same as the old value.
+  proxy.set('content', content1);
+
+  equal(watcherCount(item1a, 'id'), 3);
+  equal(watcherCount(item1b, 'id'), 3);
+  equal(watcherCount(item1c, 'id'), 3);
+
+  // This is repeated to catch the regression. It should still be a no-op.
+  proxy.set('content', content1);
+
+  equal(watcherCount(item1a, 'id'), 3);
+  equal(watcherCount(item1b, 'id'), 3);
+  equal(watcherCount(item1c, 'id'), 3);
+
+  // Set the content to a new array with completely different items and
+  // repeat the process.
+  let item2a = { id: 4 };
+  let item2b = { id: 5 };
+  let item2c = { id: 6 };
+  let content2 = A([item2a, item2b, item2c]);
+
+  addObserver(item2a, 'id', function() { });
+  addObserver(item2b, 'id', function() { });
+  addObserver(item2c, 'id', function() { });
+
+  proxy.set('content', content2);
+
+  deepEqual(get(obj, 'ids'), [4, 5, 6]);
+
+  equal(watcherCount(item2a, 'id'), 3);
+  equal(watcherCount(item2b, 'id'), 3);
+  equal(watcherCount(item2c, 'id'), 3);
+
+  // Ensure that the observers added by the EachProxy on all items in the
+  // first content array have been torn down.
+  equal(watcherCount(item1a, 'id'), 1);
+  equal(watcherCount(item1b, 'id'), 1);
+  equal(watcherCount(item1c, 'id'), 1);
+
+  proxy.set('content', content2);
+
+  equal(watcherCount(item2a, 'id'), 3);
+  equal(watcherCount(item2b, 'id'), 3);
+  equal(watcherCount(item2c, 'id'), 3);
+
+  proxy.set('content', content2);
+
+  equal(watcherCount(item2a, 'id'), 3);
+  equal(watcherCount(item2b, 'id'), 3);
+  equal(watcherCount(item2c, 'id'), 3);
+});