fix(animationFrameScheduler): some tasks are never flushed and sometimes it breaks completely

spec/schedulers/AnimationFrameScheduler-spec.ts

@@ -141,6 +141,46 @@ describe('Scheduler.animationFrame', () => {
     }
   });
 
+  it('should schedule next frame actions from a delayed one', (done) => {
+    animationFrame.schedule(() => {
+      animationFrame.schedule(() => { done(); });
+    }, 1);
+  });
+
+  it('should schedule 2 actions for a subsequent frame', (done) => {
+    let runFirst = false;
+    animationFrame.schedule(() => {
+      animationFrame.schedule(() => { runFirst = true; });
+      animationFrame.schedule(() => {
+        if (runFirst) {
+          done();
+        } else {
+          done(new Error('First action did not run'));
+        }
+      });
+    });
+  });
+
+  it('should handle delayed action without affecting next frame actions', (done) => {
+    let runDelayed = false;
+    let runFirst = false;
+    animationFrame.schedule(() => {
+      animationFrame.schedule(() => { runFirst = true; });
+      animationFrame.schedule(() => {
+        if (!runDelayed) {
+          done(new Error('Delayed action did not run'));
+        } else if (!runFirst) {
+          done(new Error('First action did not run'));
+        } else {
+          done();
+        }
+      });
+
+      // This action will execute before the next frame because the delay is less than the one of the frame
+      animationFrame.schedule(() => { runDelayed = true; }, 1);
+    });
+  });
+
   it('should not execute rescheduled actions when flushing', (done) => {
     let flushCount = 0;
     let scheduledIndices: number[] = [];

spec/schedulers/AsapScheduler-spec.ts

@@ -66,7 +66,7 @@ describe('Scheduler.asap', () => {
     const sandbox = sinon.createSandbox();
     const fakeTimer = sandbox.useFakeTimers();
     // callThrough is missing from the declarations installed by the typings tool in stable
-    const stubSetInterval = (<any> sandbox.stub(global, 'setInterval')).callThrough();
+    const stubSetInterval = (<any> sandbox.stub(fakeTimer, 'setInterval')).callThrough();
     const period = 50;
     const state = { index: 0, period };
     type State = typeof state;
@@ -92,7 +92,7 @@ describe('Scheduler.asap', () => {
     const sandbox = sinon.createSandbox();
     const fakeTimer = sandbox.useFakeTimers();
     // callThrough is missing from the declarations installed by the typings tool in stable
-    const stubSetInterval = (<any> sandbox.stub(global, 'setInterval')).callThrough();
+    const stubSetInterval = (<any> sandbox.stub(fakeTimer, 'setInterval')).callThrough();
     const period = 50;
     const state = { index: 0, period };
     type State = typeof state;
@@ -148,6 +148,12 @@ describe('Scheduler.asap', () => {
     }, 0, 0);
   });
 
+  it('should schedule asap actions from a delayed one', (done) => {
+    asap.schedule(() => {
+      asap.schedule(() => { done(); });
+    }, 1);
+  });
+
   it('should cancel the setImmediate if all scheduled actions unsubscribe before it executes', (done) => {
     let asapExec1 = false;
     let asapExec2 = false;

src/internal/scheduler/AnimationFrameAction.ts

@@ -33,7 +33,7 @@ export class AnimationFrameAction<T> extends AsyncAction<T> {
     // cancel the requested animation frame and set the scheduled flag to
     // undefined so the next AnimationFrameAction will request its own.
     const { actions } = scheduler;
-    if (id != null && actions[actions.length - 1]?.id !== id) {
+    if (id != null && id === scheduler._scheduled && actions[actions.length - 1]?.id !== id) {
       animationFrameProvider.cancelAnimationFrame(id as number);
       scheduler._scheduled = undefined;
     }

src/internal/scheduler/AnimationFrameScheduler.ts

@@ -13,8 +13,13 @@ export class AnimationFrameScheduler extends AsyncScheduler {
     // are removed from the actions array and that can shift actions that are
     // scheduled to be executed in a subsequent flush into positions at which
     // they are executed within the current flush.
-    const flushId = this._scheduled;
-    this._scheduled = undefined;
+    let flushId;
+    if (action) {
+      flushId = action.id;
+    } else {
+      flushId = this._scheduled;
+      this._scheduled = undefined;
+    }
 
     const { actions } = this;
     let error: any;