feat(ngRepeat): expose the iterating properties over the alias

Expose the properties `$index`, `$first`, `$middle`, `$last`, `$odd`
and `$even` as part of the alias

Closes #9582

Author: lgalfaso

src/ng/directive/ngRepeat.js

@@ -211,18 +211,21 @@
 var ngRepeatDirective = ['$parse', '$animate', function($parse, $animate) {
   var NG_REMOVED = '$$NG_REMOVED';
   var ngRepeatMinErr = minErr('ngRepeat');
+  var nullAliasProperties = {};
 
-  var updateScope = function(scope, index, valueIdentifier, value, keyIdentifier, key, arrayLength) {
+  var updateScope = function(scope, index, valueIdentifier, value, keyIdentifier, key, arrayLength, aliasAs) {
+    var aliasRef = aliasAs ? {} : nullAliasProperties;
     // TODO(perf): generate setters to shave off ~40ms or 1-1.5%
     scope[valueIdentifier] = value;
     if (keyIdentifier) scope[keyIdentifier] = key;
-    scope.$index = index;
-    scope.$first = (index === 0);
-    scope.$last = (index === (arrayLength - 1));
-    scope.$middle = !(scope.$first || scope.$last);
+    aliasRef.$index = scope.$index = index;
+    aliasRef.$first = scope.$first = (index === 0);
+    aliasRef.$last = scope.$last = (index === (arrayLength - 1));
+    aliasRef.$middle = scope.$middle = !(scope.$first || scope.$last);
     // jshint bitwise: false
-    scope.$odd = !(scope.$even = (index&1) === 0);
+    aliasRef.$odd = scope.$odd = !(aliasRef.$even = scope.$even = (index&1) === 0);
     // jshint bitwise: true
+    if (aliasAs) scope['$' + aliasAs] = aliasRef;
   };
 
   var getBlockStart = function(block) {
@@ -411,7 +414,7 @@ var ngRepeatDirective = ['$parse', '$animate', function($parse, $animate) {
                 $animate.move(getBlockNodes(block.clone), null, jqLite(previousNode));
               }
               previousNode = getBlockEnd(block);
-              updateScope(block.scope, index, valueIdentifier, value, keyIdentifier, key, collectionLength);
+              updateScope(block.scope, index, valueIdentifier, value, keyIdentifier, key, collectionLength, aliasAs);
             } else {
               // new item which we don't know about
               $transclude(function ngRepeatTransclude(clone, scope) {
@@ -428,7 +431,7 @@ var ngRepeatDirective = ['$parse', '$animate', function($parse, $animate) {
                 // by a directive with templateUrl when its template arrives.
                 block.clone = clone;
                 nextBlockMap[block.id] = block;
-                updateScope(block.scope, index, valueIdentifier, value, keyIdentifier, key, collectionLength);
+                updateScope(block.scope, index, valueIdentifier, value, keyIdentifier, key, collectionLength, aliasAs);
               });
             }
           }

test/ng/directive/ngRepeatSpec.js

@@ -492,6 +492,43 @@ describe('ngRepeat', function() {
         return text.replace(/[\-\[\]\/\{\}\(\)\*\+\?\.\\\^\$\|]/g, "\\$&");
       }
     }));
+
+    it('should expose the index properties using `${{userSpecifiedAliasName}}`', inject(function() {
+      var expression = '{{item}}-{{$results.' + ['$index', '$first', '$middle', '$last', '$odd', '$even'].join('}}-{{$results.') + '}}:';
+      element = $compile(
+        '<div>' +
+        '  <div ng-repeat="item in items as results">' + expression + '</div>' +
+        '</div>')(scope);
+
+      scope.items = ['a','b','c','d','e','f'];
+      scope.$digest();
+      expect(trim(element.text())).toEqual(
+          'a-0-true-false-false-false-true:' +
+          'b-1-false-true-false-true-false:' +
+          'c-2-false-true-false-false-true:' +
+          'd-3-false-true-false-true-false:' +
+          'e-4-false-true-false-false-true:' +
+          'f-5-false-false-true-true-false:');
+
+      scope.items.shift();
+      scope.$digest();
+      expect(trim(element.text())).toEqual(
+          'b-0-true-false-false-false-true:' +
+          'c-1-false-true-false-true-false:' +
+          'd-2-false-true-false-false-true:' +
+          'e-3-false-true-false-true-false:' +
+          'f-4-false-false-true-false-true:');
+    }));
+
+    it('should be possible to access the alias inside the loop', inject(function() {
+      element = $compile(
+        '<div>' +
+        '  <div ng-repeat="item in items as results">{{results[$index]}}</div>' +
+        '</div>')(scope);
+      scope.items = ['a','b','c','d','e','f'];
+      scope.$digest();
+      expect(trim(element.text())).toEqual('abcdef');
+    }));
   });