Pass index into computed array callbacks

packages/ember-runtime/lib/computed/reduce_computed_macros.js

@@ -154,16 +154,17 @@ export function min(dependentKey) {
 
   The callback method you provide should have the following signature.
   `item` is the current item in the iteration.
+  `index` is the integer index of the current item in the iteration.
 
   ```javascript
-  function(item);
+  function(item, index);
   ```
 
   Example
 
   ```javascript
   var Hamster = Ember.Object.extend({
-    excitingChores: Ember.computed.map('chores', function(chore) {
+    excitingChores: Ember.computed.map('chores', function(chore, index) {
       return chore.toUpperCase() + '!';
     })
   });
@@ -184,7 +185,7 @@ export function min(dependentKey) {
 export function map(dependentKey, callback) {
   var options = {
     addedItem: function(array, item, changeMeta, instanceMeta) {
-      var mapped = callback.call(this, item);
+      var mapped = callback.call(this, item, changeMeta.index);
       array.insertAt(changeMeta.index, mapped);
       return array;
     },
@@ -245,14 +246,15 @@ export var mapProperty = mapBy;
 
   The callback method you provide should have the following signature.
   `item` is the current item in the iteration.
+  `index` is the integer index of the current item in the iteration.
 
   ```javascript
-  function(item);
+  function(item, index);
   ```
 
   ```javascript
   var Hamster = Ember.Object.extend({
-    remainingChores: Ember.computed.filter('chores', function(chore) {
+    remainingChores: Ember.computed.filter('chores', function(chore, index) {
       return !chore.done;
     })
   });
@@ -281,7 +283,7 @@ export function filter(dependentKey, callback) {
     },
 
     addedItem: function (array, item, changeMeta, instanceMeta) {
-      var match = !!callback.call(this, item);
+      var match = !!callback.call(this, item, changeMeta.index);
       var filterIndex = instanceMeta.filteredArrayIndexes.addItem(changeMeta.index, match);
 
       if (match) {

packages/ember-runtime/tests/computed/reduce_computed_macros_test.js

@@ -119,6 +119,20 @@ test("it maps simple unshifted properties", function() {
   deepEqual(get(obj, 'mapped'), ['A', 'B'], "properties unshifted in sequence are mapped correctly");
 });
 
+test("it passes the index to the callback", function() {
+  var array = Ember.A(['a', 'b', 'c']);
+
+  run(function() {
+    obj = EmberObject.createWithMixins({
+      array: array,
+      mapped: computedMap('array', function (item, index) { return index; })
+    });
+    get(obj, 'mapped');
+  });
+
+  deepEqual(get(obj, 'mapped'), [0, 1, 2], "index is passed to callback correctly");
+});
+
 test("it maps objects", function() {
   deepEqual(get(obj, 'mappedObjects'), [{ name: 'Robert'}, { name: 'Leanna' }]);
 
@@ -245,6 +259,20 @@ test("it filters according to the specified filter function", function() {
   deepEqual(filtered, [2,4,6,8], "computedFilter filters by the specified function");
 });
 
+test("it passes the index to the callback", function() {
+  var array = Ember.A(['a', 'b', 'c']);
+
+  run(function() {
+    obj = EmberObject.createWithMixins({
+      array: array,
+      filtered: computedFilter('array', function (item, index) { return index === 1; })
+    });
+    get(obj, 'filtered');
+  });
+
+  deepEqual(get(obj, 'filtered'), ['b'], "index is passed to callback correctly");
+});
+
 test("it caches properly", function() {
   var array = get(obj, 'array'),
       filtered = get(obj, 'filtered');