feat(TypeScript): fromPromise accepts PromiseLike object (#2505)

* fix(PromiseObservable): can not create observable from promise conform to Promises/A+ spec

* docs(PromiseObservable): update the doc to reflect more relaxed type of promise

* test(fromPromise): ensure Observables can be created from other promise implementations

spec/observables/from-promise-spec.ts

@@ -72,6 +72,25 @@ describe('Observable.fromPromise', () => {
  });
  });
 
+ it('should accept PromiseLike object for interoperability', (done: MochaDone) => {
+ class CustomPromise<T> implements PromiseLike<T> {
+ constructor(private promise: PromiseLike<T>) {
+ }
+ then(onFulfilled?, onRejected?): PromiseLike<T> {
+ return new CustomPromise(this.promise.then(onFulfilled, onRejected));
+ };
+ }
+ const promise = new CustomPromise(Promise.resolve(42));
+ Observable.fromPromise(promise)
+ .subscribe(
+ (x: number) => { expect(x).to.equal(42); },
+ () => {
+ done(new Error('should not be called'));
+ }, () => {
+ done();
+ });
+ });
+
  it('should emit a value from a resolved promise on a separate scheduler', (done: MochaDone) => {
  const promise = Promise.resolve(42);
  Observable.fromPromise(promise, Rx.Scheduler.asap)

src/observable/PromiseObservable.ts

@@ -31,19 +31,19 @@ export class PromiseObservable<T> extends Observable<T> {
  * @see {@link bindCallback}
  * @see {@link from}
  *
- * @param {Promise<T>} promise The promise to be converted.
+ * @param {PromiseLike<T>} promise The promise to be converted.
  * @param {Scheduler} [scheduler] An optional IScheduler to use for scheduling
  * the delivery of the resolved value (or the rejection).
  * @return {Observable<T>} An Observable which wraps the Promise.
  * @static true
  * @name fromPromise
  * @owner Observable
  */
- static create<T>(promise: Promise<T>, scheduler?: IScheduler): Observable<T> {
+ static create<T>(promise: PromiseLike<T>, scheduler?: IScheduler): Observable<T> {
  return new PromiseObservable(promise, scheduler);
  }
 
- constructor(private promise: Promise<T>, private scheduler?: IScheduler) {
+ constructor(private promise: PromiseLike<T>, private scheduler?: IScheduler) {
  super();
  }