fix(common): introduce isObservable method (#14067)

Closes #8848

PR Close #14067

modules/@angular/common/src/pipes/async_pipe.ts

@@ -8,7 +8,7 @@
 
 import {ChangeDetectorRef, OnDestroy, Pipe, PipeTransform, WrappedValue} from '@angular/core';
 import {EventEmitter, Observable} from '../facade/async';
-import {isPromise} from '../private_import_core';
+import {isObservable, isPromise} from '../private_import_core';
 import {InvalidPipeArgumentError} from './invalid_pipe_argument_error';
 
 interface SubscriptionStrategy {
@@ -116,7 +116,7 @@ export class AsyncPipe implements OnDestroy, PipeTransform {
       return _promiseStrategy;
     }
 
-    if ((<any>obj).subscribe) {
+    if (isObservable(obj)) {
       return _observableStrategy;
     }
 

modules/@angular/common/src/private_import_core.ts

@@ -9,3 +9,4 @@
 import {__core_private__ as r} from '@angular/core';
 
 export const isPromise: typeof r.isPromise = r.isPromise;
+export const isObservable: typeof r.isObservable = r.isObservable;

modules/@angular/core/src/core_private_export.ts

@@ -41,7 +41,7 @@ import * as reflector_reader from './reflection/reflector_reader';
 import * as reflection_types from './reflection/types';
 import * as api from './render/api';
 import * as decorators from './util/decorators';
-import {isPromise} from './util/lang';
+import {isObservable, isPromise} from './util/lang';
 
 export const __core_private__: {
   isDefaultChangeDetectionStrategy: typeof constants.isDefaultChangeDetectionStrategy,
@@ -107,6 +107,7 @@ export const __core_private__: {
   _ComponentStillLoadingError?: ComponentStillLoadingError,
   ComponentStillLoadingError: typeof ComponentStillLoadingError,
   isPromise: typeof isPromise,
+  isObservable: typeof isObservable,
   AnimationTransition: typeof AnimationTransition
   view_utils: typeof view_utils,
 } = {
@@ -157,5 +158,6 @@ export const __core_private__: {
   FILL_STYLE_FLAG: FILL_STYLE_FLAG_,
   ComponentStillLoadingError: ComponentStillLoadingError,
   isPromise: isPromise,
+  isObservable: isObservable,
   AnimationTransition: AnimationTransition
 };

modules/@angular/core/src/util/lang.ts

@@ -6,6 +6,9 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
+import {Observable} from 'rxjs/Observable';
+import {$$observable as symbolObservable} from 'rxjs/symbol/observable';
+
 /**
  * Determine if the argument is shaped like a Promise
  */
@@ -14,3 +17,10 @@ export function isPromise(obj: any): obj is Promise<any> {
   // It's up to the caller to ensure that obj.then conforms to the spec
   return !!obj && typeof obj.then === 'function';
 }
+
+/**
+ * Determine if the argument is an Observable
+ */
+export function isObservable(obj: any | Observable<any>): obj is Observable<any> {
+  return !!(obj && obj[symbolObservable]);
+}

modules/@angular/core/test/util/lang_spec.ts

@@ -5,7 +5,8 @@
  * Use of this source code is governed by an MIT-style license that can be
  * found in the LICENSE file at https://angular.io/license
  */
-import {isPromise} from '@angular/core/src/util/lang';
+import {isObservable, isPromise} from '@angular/core/src/util/lang';
+import {of } from 'rxjs/observable/of';
 
 export function main() {
   describe('isPromise', () => {
@@ -25,4 +26,22 @@ export function main() {
       expect(isPromise(null)).toEqual(false);
     });
   });
+
+  describe('isObservable', () => {
+    it('should be true for an Observable', () => expect(isObservable(of (true))).toEqual(true));
+
+    it('should be false if the argument is undefined',
+       () => expect(isObservable(undefined)).toEqual(false));
+
+    it('should be false if the argument is null', () => expect(isObservable(null)).toEqual(false));
+
+    it('should be false if the argument is an object',
+       () => expect(isObservable({})).toEqual(false));
+
+    it('should be false if the argument is a function',
+       () => expect(isObservable(() => {})).toEqual(false));
+
+    it('should be false if the argument is the object with subscribe function',
+       () => expect(isObservable({subscribe: () => {}})).toEqual(false));
+  });
 }

modules/@angular/router/src/private_import_core.ts

@@ -0,0 +1,12 @@
+/**
+ * @license
+ * Copyright Google Inc. All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+
+import {__core_private__ as r} from '@angular/core';
+
+export const isPromise: typeof r.isPromise = r.isPromise;
+export const isObservable: typeof r.isObservable = r.isObservable;

modules/@angular/router/src/utils/collection.ts

@@ -16,6 +16,7 @@ import * as l from 'rxjs/operator/last';
 import {map} from 'rxjs/operator/map';
 import {mergeAll} from 'rxjs/operator/mergeAll';
 
+import {isObservable, isPromise} from '../private_import_core';
 import {PRIMARY_OUTLET} from '../shared';
 
 export function shallowEqualArrays(a: any[], b: any[]): boolean {
@@ -129,11 +130,11 @@ export function andObservables(observables: Observable<Observable<any>>): Observ
 
 export function wrapIntoObservable<T>(value: T | NgModuleFactory<T>| Promise<T>| Observable<T>):
     Observable<T> {
-  if (value instanceof Observable) {
+  if (isObservable(value)) {
     return value;
   }
 
-  if (value instanceof Promise) {
+  if (isPromise(value)) {
     return fromPromise(value);
   }