Allow properties on functions to be watchable/streamable

packages/ember-metal/lib/chains.js

@@ -10,12 +10,17 @@ function firstKey(path) {
   return path.match(FIRST_KEY)[0];
 }
 
-function isObject(obj) {
-  return obj && (typeof obj === 'object');
+function isWatchable(obj) {
+  if (!obj) {
+    return;
+  }
+
+  let type = typeof obj;
+  return type === 'object' || type === 'function';
 }
 
 function isVolatile(obj) {
-  return !(isObject(obj) && obj.isDescriptor && obj._cacheable);
+  return !(isWatchable(obj) && obj.isDescriptor && obj._cacheable);
 }
 
 function Chains() { }
@@ -42,7 +47,7 @@ export function flushPendingChains() {
 }
 
 function addChainWatcher(obj, keyName, node) {
-  if (!isObject(obj)) {
+  if (!isWatchable(obj)) {
     return;
   }
 
@@ -63,7 +68,7 @@ function addChainWatcher(obj, keyName, node) {
 }
 
 function removeChainWatcher(obj, keyName, node) {
-  if (!isObject(obj)) {
+  if (!isWatchable(obj)) {
     return;
   }
 

packages/ember-metal/lib/streams/key-stream.js

@@ -60,7 +60,8 @@ merge(KeyStream.prototype, {
     if (object !== this.observedObject) {
       this._clearObservedObject();
 
-      if (object && typeof object === 'object') {
+      var type = typeof object;
+      if (object && (type === 'object' || type === 'function')) {
         addObserver(object, this.key, this, this.notify);
         this.observedObject = object;
       }

packages/ember-metal/tests/streams/key-stream-test.js

@@ -48,6 +48,23 @@ QUnit.test('is notified when the observed object\'s property is mutated', functi
   equal(nameStream.value(), 'wycats', 'Stream value is correct');
 });
 
+QUnit.test('is notified when properties on functions are mutated', function() {
+  var fn = function() {};
+  fn.foo = 'mmun';
+  source = new Stream(function() { return fn; });
+
+  var nameStream = source.get('foo');
+  nameStream.subscribe(incrementCount);
+
+  equal(count, 0, 'Subscribers called correct number of times');
+  equal(nameStream.value(), 'mmun', 'Stream value is correct');
+
+  set(fn, 'foo', 'wycats');
+
+  equal(count, 1, 'Subscribers called correct number of times');
+  equal(nameStream.value(), 'wycats', 'Stream value is correct');
+});
+
 QUnit.test('is notified when the source stream\'s value changes to a new object', function() {
   var nameStream = source.get('name');
   nameStream.subscribe(incrementCount);

packages/ember-metal/tests/watching/watch_test.js

@@ -271,3 +271,22 @@ testBoth('watching "length" property on an array', function(get, set) {
   equal(get(arr, 'length'), 10, 'should get new value');
   equal(arr.length, 10, 'property should be accessible on arr');
 });
+
+testBoth('watching properties on a function', function(get, set) {
+  var obj = {
+    foo: function() {}
+  };
+  addListeners(obj, 'foo.baz');
+
+  watch(obj, 'foo.baz');
+  equal(get(obj, 'foo.baz'), undefined, 'should have original prop');
+
+  set(obj, 'foo.baz', 'bar');
+  equal(willCount, 1, 'should have invoked willCount');
+  equal(didCount, 1, 'should have invoked didCount');
+
+  equal(get(obj, 'foo.baz'), 'bar', 'should get new value');
+  equal(obj.foo.baz, 'bar', 'property should be accessible on obj');
+});
+
+