fix: animationFrameScheduler and asapScheduler no longer executing actions

Fixes ReactiveX#6854

Author: ajafff

spec/schedulers/AnimationFrameScheduler-spec.ts

@@ -1,6 +1,6 @@
 import { expect } from 'chai';
 import * as sinon from 'sinon';
-import { animationFrameScheduler, Subscription, merge } from 'rxjs';
+import {animationFrameScheduler, Subscription, merge, SchedulerAction} from 'rxjs';
 import { delay } from 'rxjs/operators';
 import { TestScheduler } from 'rxjs/testing';
 import { observableMatcher } from '../helpers/observableMatcher';
@@ -238,4 +238,27 @@ describe('Scheduler.animationFrame', () => {
       done();
     });
   });
+
+  it('should handle actions scheduled during flush before current action is rescheduled', (done) => {
+    const sandbox = sinon.createSandbox();
+
+    const result: string[] = [];
+    let reschedule = true;
+    function work(this: SchedulerAction<unknown>) {
+      result.push('work');
+      if (reschedule) {
+        animationFrameScheduler.schedule(() => result.push('task 1'));
+        animationFrameScheduler.schedule(() => result.push('task 2'));
+        this.schedule();
+        expect(result).to.deep.equal(['work']);
+        reschedule = false;
+      } else {
+        expect(result).to.deep.equal(['work', 'task 1', 'task 2', 'work']);
+        sandbox.restore();
+        done();
+      }
+    }
+    animationFrameScheduler.schedule(work);
+    expect(result).to.deep.equal([]);
+  });
 });

spec/schedulers/AsapScheduler-spec.ts

@@ -1,6 +1,6 @@
 import { expect } from 'chai';
 import * as sinon from 'sinon';
-import { asapScheduler, Subscription, SchedulerAction, merge } from 'rxjs';
+import {asapScheduler, Subscription, SchedulerAction, merge, animationFrameScheduler} from 'rxjs';
 import { delay } from 'rxjs/operators';
 import { TestScheduler } from 'rxjs/testing';
 import { observableMatcher } from '../helpers/observableMatcher';
@@ -288,4 +288,27 @@ describe('Scheduler.asap', () => {
       done();
     });
   });
+
+  it('should handle actions scheduled during flush before current action is rescheduled', (done) => {
+    const sandbox = sinon.createSandbox();
+
+    const result: string[] = [];
+    let reschedule = true;
+    function work(this: SchedulerAction<unknown>) {
+      result.push('work');
+      if (reschedule) {
+        asapScheduler.schedule(() => result.push('task 1'));
+        asapScheduler.schedule(() => result.push('task 2'));
+        this.schedule();
+        expect(result).to.deep.equal(['work']);
+        reschedule = false;
+      } else {
+        expect(result).to.deep.equal(['work', 'task 1', 'task 2', 'work']);
+        sandbox.restore();
+        done();
+      }
+    }
+    asapScheduler.schedule(work);
+    expect(result).to.deep.equal([]);
+  });
 });

src/internal/scheduler/AnimationFrameAction.ts

@@ -27,10 +27,10 @@ export class AnimationFrameAction<T> extends AsyncAction<T> {
     if ((delay != null && delay > 0) || (delay == null && this.delay > 0)) {
       return super.recycleAsyncId(scheduler, id, delay);
     }
-    // If the scheduler queue has no remaining actions with the same async id,
+    // If the scheduler queue has no remaining actions for the next schedule,
     // cancel the requested animation frame and set the scheduled flag to
     // undefined so the next AnimationFrameAction will request its own.
-    if (!scheduler.actions.some((action) => action.id === id)) {
+    if (scheduler._scheduled === id && !scheduler.actions.some((action) => action.id === id)) {
       animationFrameProvider.cancelAnimationFrame(id);
       scheduler._scheduled = undefined;
     }

src/internal/scheduler/AsapAction.ts

@@ -27,10 +27,10 @@ export class AsapAction<T> extends AsyncAction<T> {
     if ((delay != null && delay > 0) || (delay == null && this.delay > 0)) {
       return super.recycleAsyncId(scheduler, id, delay);
     }
-    // If the scheduler queue has no remaining actions with the same async id,
+    // If the scheduler queue has no remaining actions for the next schedule,
     // cancel the requested microtask and set the scheduled flag to undefined
     // so the next AsapAction will request its own.
-    if (!scheduler.actions.some((action) => action.id === id)) {
+    if (scheduler._scheduled === id && !scheduler.actions.some((action) => action.id === id)) {
       immediateProvider.clearImmediate(id);
       scheduler._scheduled = undefined;
     }