fix(EventEmitter): resolve onError and onComplete asynchronously

closes #4443

modules/angular2/src/facade/async.ts

@@ -1,4 +1,4 @@
-import {global, isPresent} from 'angular2/src/facade/lang';
+import {global, isPresent, noop} from 'angular2/src/facade/lang';
 // We make sure promises are in a separate file so that we can use promises
 // without depending on rxjs.
 import {PromiseWrapper, Promise, PromiseCompleter} from 'angular2/src/facade/promise';
@@ -27,6 +27,8 @@ export class ObservableWrapper {
   // TODO(vsavkin): when we use rxnext, try inferring the generic type from the first arg
   static subscribe<T>(emitter: any, onNext: (value: T) => void, onError?: (exception: any) => void,
                       onComplete: () => void = () => {}): Object {
+    onError = (typeof onError === "function") && onError || noop;
+    onComplete = (typeof onComplete === "function") && onComplete || noop;
     return emitter.subscribe({next: onNext, error: onError, complete: onComplete});
   }
 
@@ -117,20 +119,39 @@ export class EventEmitter<T> extends Subject<T> {
   next(value: any) { super.next(value); }
 
   subscribe(generatorOrNext?: any, error?: any, complete?: any): any {
-    if (generatorOrNext && typeof generatorOrNext === 'object') {
-      let schedulerFn = this._isAsync ?
-                            (value) => { setTimeout(() => generatorOrNext.next(value)); } :
-                            (value) => { generatorOrNext.next(value); };
-      return super.subscribe(schedulerFn,
-                             (err) => generatorOrNext.error ? generatorOrNext.error(err) : null,
-                             () => generatorOrNext.complete ? generatorOrNext.complete() : null);
-    } else {
-      let schedulerFn = this._isAsync ? (value) => { setTimeout(() => generatorOrNext(value)); } :
-                                        (value) => { generatorOrNext(value); };
+    let schedulerFn;
+    let errorFn = (err: any) => null;
+    let completeFn = () => null;
 
-      return super.subscribe(schedulerFn, (err) => error ? error(err) : null,
-                             () => complete ? complete() : null);
+    if (generatorOrNext && typeof generatorOrNext === 'object') {
+      schedulerFn = this._isAsync ? (value) => { setTimeout(() => generatorOrNext.next(value)); } :
+                                    (value) => { generatorOrNext.next(value); };
+
+      if (generatorOrNext.error) {
+        errorFn = this._isAsync ? (err) => { setTimeout(() => generatorOrNext.error(err)); } :
+                                  (err) => { generatorOrNext.error(err); };
+      }
+
+      if (generatorOrNext.complete) {
+        completeFn = this._isAsync ? () => { setTimeout(() => generatorOrNext.complete()); } :
+                                     () => { generatorOrNext.complete(); };
+      }
+    } else {
+      schedulerFn = this._isAsync ? (value) => { setTimeout(() => generatorOrNext(value)); } :
+                                    (value) => { generatorOrNext(value); };
+
+      if (error) {
+        errorFn =
+            this._isAsync ? (err) => { setTimeout(() => error(err)); } : (err) => { error(err); };
+      }
+
+      if (complete) {
+        completeFn =
+            this._isAsync ? () => { setTimeout(() => complete()); } : () => { complete(); };
+      }
     }
+
+    return super.subscribe(schedulerFn, errorFn, completeFn);
   }
 }
 

modules/angular2/src/facade/lang.ts

@@ -126,6 +126,8 @@ export function isDate(obj): boolean {
   return obj instanceof Date && !isNaN(obj.valueOf());
 }
 
+export function noop() {}
+
 export function stringify(token): string {
   if (typeof token === 'string') {
     return token;