feat(Events): allow a different local vs public name

closes angular#2272

Author: vicb

modules/angular2/src/core/annotations_impl/annotations.ts

@@ -550,7 +550,7 @@ export class Directive extends Injectable {
    *   events: ['statusChange']
    * })
    * class TaskComponent {
-   *   statusChange:EventEmitter;
+   *   statusChange: EventEmitter;
    *
    *   constructor() {
    *     this.statusChange = new EventEmitter();
@@ -561,6 +561,26 @@ export class Directive extends Injectable {
    *   }
    * }
    * ```
+   *
+   * Use `propertyName: eventName` when the event emitter property name is different from the name
+   * of the emitted event:
+   *
+   * @Component({
+   *   events: ['status: statusChange']
+   * })
+   * class TaskComponent {
+   *   status: EventEmitter;
+   *
+   *   constructor() {
+   *     this.status = new EventEmitter();
+   *   }
+   *
+   *   onComplete() {
+   *     this.status.next('completed');
+   *   }
+   * }
+   * ```
+   *
    */
   events: List<string>;
 

modules/angular2/src/core/compiler/element_injector.ts

@@ -4,7 +4,8 @@ import {
   Type,
   BaseException,
   stringify,
-  CONST_EXPR
+  CONST_EXPR,
+  StringWrapper
 } from 'angular2/src/facade/lang';
 import {EventEmitter, ObservableWrapper} from 'angular2/src/facade/async';
 import {List, ListWrapper, MapWrapper, StringMapWrapper} from 'angular2/src/facade/collection';
@@ -382,8 +383,20 @@ export class BindingData {
   createEventEmitterAccessors() {
     if (!(this.binding instanceof DirectiveBinding)) return [];
     var db = <DirectiveBinding>this.binding;
-    return ListWrapper.map(db.eventEmitters, eventName => new EventEmitterAccessor(
-                                                 eventName, reflector.getter(eventName)));
+    return ListWrapper.map(db.eventEmitters, eventConfig => {
+      let fieldName;
+      let eventName;
+      var colonIdx = eventConfig.indexOf(':');
+      if (colonIdx > -1) {
+        // long format: 'fieldName: eventName'
+        fieldName = StringWrapper.substring(eventConfig, 0, colonIdx).trim();
+        eventName = StringWrapper.substring(eventConfig, colonIdx + 1).trim();
+      } else {
+        // short format: 'name' when fieldName and eventName are the same
+        fieldName = eventName = eventConfig;
+      }
+      return new EventEmitterAccessor(eventName, reflector.getter(fieldName))
+    });
   }
 
   createHostActionAccessors() {

modules/angular2/test/core/compiler/element_injector_spec.ts

@@ -418,6 +418,18 @@ export function main() {
         expect(accessor.getter(new HasEventEmitter())).toEqual('emitter');
       });
 
+      it('should allow a different internal vs public name', () => {
+        var binding = DirectiveBinding.createFromType(HasEventEmitter,
+                                                      new dirAnn.Directive({events: ['emitter: publicEmitter']}));
+
+        var inj = createPei(null, 0, [binding]);
+        expect(inj.eventEmitterAccessors.length).toEqual(1);
+
+        var accessor = inj.eventEmitterAccessors[0][0];
+        expect(accessor.eventName).toEqual('publicEmitter');
+        expect(accessor.getter(new HasEventEmitter())).toEqual('emitter');
+      });
+
       it('should return a list of hostAction accessors', () => {
         var binding = DirectiveBinding.createFromType(
             HasEventEmitter, new dirAnn.Directive({hostActions: {'hostActionName': 'onAction'}}));