fix(ngOptions): do not watch properties starting with $

Expressions that compute labels and track by values for ngOptions were
being called for properties, that start with $ even though those properties
were being ignored as options.

Closes angular#11930
Closes angular#12010

Author: petebacondarwin

src/ng/directive/ngOptions.js

@@ -303,6 +303,7 @@ var ngOptionsDirective = ['$compile', '$parse', function($compile, $parse) {
         values = values || [];
 
         Object.keys(values).forEach(function getWatchable(key) {
+          if (key.charAt(0) === '$') return;
           var locals = getLocals(values[key], key);
           var selectValue = getTrackByValueFn(values[key], locals);
           watchedArray.push(selectValue);

test/ng/directive/ngOptionsSpec.js

@@ -448,6 +448,41 @@ describe('ngOptions', function() {
   });
 
 
+  it('should not watch array properties that start with $ or $$', function() {
+    createSelect({
+      'ng-options': 'value as createLabel(value) for value in array',
+      'ng-model': 'selected'
+    });
+    scope.createLabel = jasmine.createSpy('createLabel').andCallFake(function(value) { return value; });
+    scope.array = ['a', 'b', 'c'];
+    scope.array.$$private = 'do not watch';
+    scope.array.$property = 'do not watch';
+    scope.selected = 'b';
+    scope.$digest();
+
+    expect(scope.createLabel).toHaveBeenCalledWith('a');
+    expect(scope.createLabel).toHaveBeenCalledWith('b');
+    expect(scope.createLabel).toHaveBeenCalledWith('c');
+    expect(scope.createLabel).not.toHaveBeenCalledWith('do not watch');
+  });
+
+
+  it('should not watch object properties that start with $ or $$', function() {
+    createSelect({
+      'ng-options': 'key as createLabel(key) for (key, value) in object',
+      'ng-model': 'selected'
+    });
+    scope.createLabel = jasmine.createSpy('createLabel').andCallFake(function(value) { return value; });
+    scope.object = {'regularProperty': 'visible', '$$private': 'invisible', '$property': 'invisible'};
+    scope.selected = 'regularProperty';
+    scope.$digest();
+
+    expect(scope.createLabel).toHaveBeenCalledWith('regularProperty');
+    expect(scope.createLabel).not.toHaveBeenCalledWith('$$private');
+    expect(scope.createLabel).not.toHaveBeenCalledWith('$property');
+  });
+
+
   it('should allow expressions over multiple lines', function() {
     scope.isNotFoo = function(item) {
       return item.name !== 'Foo';