feat: remove async iteration (#5492)

* feat: remove async iteration

Removes experimental async iteration from Observable. Users that want this feature should really checkout https://github.com/benlesh/rxjs-for-await. There are too many edge cases for this, and also some uncertainty around cancellation behaviors we could provide. We may add this back in another iteration, but for now it is best in a separate library

BREAKING CHANGE: Removes support for `for await`. Use https://github.com/benlesh/rxjs-for-await instead.

* chore: remove unused file, fix lint

* chore: update side-effect golden files

integration/side-effects/snapshots/esm/ajax.js

@@ -1 +1 @@
-import "tslib";
+

integration/side-effects/snapshots/esm/testing.js

@@ -1,5 +1,3 @@
-import "tslib";
-
 var NotificationKind;
 
 (function(NotificationKind) {

integration/side-effects/snapshots/esm/websocket.js

@@ -1 +1 @@
-import "tslib";
+

spec/Observable-spec.ts

@@ -2,8 +2,8 @@ import { expect } from 'chai';
 import * as sinon from 'sinon';
 import { Observer, TeardownLogic } from '../src/internal/types';
 import { cold, expectObservable, expectSubscriptions } from './helpers/marble-testing';
-import { Observable, config, Subscription, noop, Subscriber, Operator, NEVER, Subject, of, throwError, empty, interval } from 'rxjs';
-import { map, multicast, refCount, filter, count, tap, combineLatest, concat, merge, race, zip, take, finalize } from 'rxjs/operators';
+import { Observable, config, Subscription, noop, Subscriber, Operator, NEVER, Subject, of, throwError, empty } from 'rxjs';
+import { map, multicast, refCount, filter, count, tap, combineLatest, concat, merge, race, zip } from 'rxjs/operators';
 
 declare const rxTestScheduler: any;
 
@@ -36,7 +36,7 @@ describe('Observable', () => {
   });
 
   it('should send errors thrown in the constructor down the error path', (done) => {
-    new Observable<number>((observer) => {
+    new Observable<number>(() => {
       throw new Error('this should be handled');
     })
       .subscribe({
@@ -68,7 +68,7 @@ describe('Observable', () => {
     });
 
     it('should reject promise when in error', (done) => {
-      throwError('bad').forEach((x) => {
+      throwError('bad').forEach(() => {
         done(new Error('should not be called'));
       }, Promise).then(() => {
         done(new Error('should not complete'));
@@ -265,7 +265,7 @@ describe('Observable', () => {
       });
 
       source.subscribe({
-        error(err) {
+        error() {
           /* noop: expected error */
         }
       });
@@ -655,7 +655,7 @@ describe('Observable.create', () => {
   });
 
   it('should send errors thrown in the passed function down the error path', (done) => {
-    Observable.create((observer: Observer<any>) => {
+    Observable.create(() => {
       throw new Error('this should be handled');
     })
       .subscribe({
@@ -719,7 +719,7 @@ describe('Observable.lift', () => {
     result.subscribe(
       function (x) {
         expect(x).to.equal(expected.shift());
-      }, (x) => {
+      }, () => {
         done(new Error('should not be called'));
       }, () => {
         done();
@@ -745,7 +745,7 @@ describe('Observable.lift', () => {
     result.subscribe(
       function (x) {
         expect(x).to.equal(expected.shift());
-      }, (x) => {
+      }, () => {
         done(new Error('should not be called'));
       }, () => {
         done();
@@ -769,7 +769,7 @@ describe('Observable.lift', () => {
     result.subscribe(
       function (x) {
         expect(x).to.equal(expected.shift());
-      }, (x) => {
+      }, () => {
         done(new Error('should not be called'));
       }, () => {
         done();
@@ -909,7 +909,7 @@ describe('Observable.lift', () => {
         function (x) {
           expect(x).to.equal(expected.shift());
         },
-        (x) => {
+        () => {
           done(new Error('should not be called'));
         }, () => {
           expect(log).to.deep.equal([
@@ -939,57 +939,3 @@ describe('Observable.lift', () => {
     }
   });
 });
-
-if (Symbol && Symbol.asyncIterator) {
-  describe('async iterator support', () => {
-    it('should work for sync observables', async () => {
-      const source = of(1, 2, 3);
-      const results: number[] = [];
-      for await (const value of source) {
-        results.push(value);
-      }
-      expect(results).to.deep.equal([1, 2, 3]);
-    });
-
-    it('should throw if the observable errors', async () => {
-      const source = throwError(new Error('bad'));
-      let error: any;
-      try {
-        for await (const _ of source) {
-          // do nothing
-        }
-      } catch (err) {
-        error = err;
-      }
-      expect(error).to.be.an.instanceOf(Error);
-      expect(error.message).to.equal('bad');
-    });
-
-    it('should support async observables', async () => {
-      const source = interval(10).pipe(take(3));
-      const results: number[] = [];
-      for await (const value of source) {
-        results.push(value);
-      }
-      expect(results).to.deep.equal([0, 1, 2]);
-    });
-
-    it('should do something clever if the loop exits', async () => {
-      let finalized = false;
-      const source = interval(10).pipe(take(10), finalize(() => finalized = true));
-      const results: number[] = [];
-      try {
-        for await (const value of source) {
-          results.push(value);
-          if (value === 1) {
-            throw new Error('bad');
-          }
-        }
-      } catch (err) {
-        // ignore
-      }
-      expect(results).to.deep.equal([0, 1]);
-      expect(finalized).to.be.true;
-    });
-  });
-}

src/internal/Observable.ts

@@ -9,7 +9,6 @@ import { throwError } from './observable/throwError';
 import { observable as Symbol_observable } from './symbol/observable';
 import { pipeFromArray } from './util/pipe';
 import { config } from './config';
-import { asyncIteratorFrom } from './asyncIteratorFrom';
 
 /**
  * A representation of any set of values over any amount of time. This is the most basic building block
@@ -396,24 +395,3 @@ function getPromiseCtor(promiseCtor: PromiseConstructorLike | undefined) {
 
   return promiseCtor;
 }
-
-export interface Observable<T> {
-  [Symbol.asyncIterator](): AsyncIterableIterator<T>;
-}
-
-(function () {
-  /**
-   * We only add this symbol if the runtime supports it.
-   * Adding this adds support for subscribing to observables
-   * via `for await(const value of source$) {}`
-   *
-   * This passes muster in Node 9, which does not support
-   * async iterators. As well as working in Node 12, which does
-   * support the symbol.
-   */
-  if (Symbol && Symbol.asyncIterator) {
-    Observable.prototype[Symbol.asyncIterator] = function () {
-      return asyncIteratorFrom(this);
-    };
-  }
-})();