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refactor(core): Do not duplicate change detection with run coalescing (part 2) #55403

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refactor(core): Do not duplicate change detection with run coalescing (part 2) #55403

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43 changes: 28 additions & 15 deletions packages/core/src/change_detection/scheduling/zoneless_scheduling_impl.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -6,6 +6,8 @@
* found in the LICENSE file at https://angular.io/license
*/

import {Subscription} from 'rxjs';

import {ApplicationRef} from '../../application/application_ref';
import {Injectable} from '../../di/injectable';
import {inject} from '../../di/injector_compatibility';
Expand Down Expand Up @@ -43,29 +45,40 @@ function trackMicrotaskNotificationForDebugging() {

@Injectable({providedIn: 'root'})
export class ChangeDetectionSchedulerImpl implements ChangeDetectionScheduler {
private appRef = inject(ApplicationRef);
private taskService = inject(PendingTasks);
private pendingRenderTaskId: number|null = null;
private shouldRefreshViews = false;
private readonly appRef = inject(ApplicationRef);
private readonly taskService = inject(PendingTasks);
private readonly ngZone = inject(NgZone);
runningTick = false;
private cancelScheduledCallback: null|(() => void) = null;
private readonly zonelessEnabled = inject(ZONELESS_ENABLED);
private readonly disableScheduling =
inject(ZONELESS_SCHEDULER_DISABLED, {optional: true}) ?? false;
private readonly zoneIsDefined = typeof Zone !== 'undefined' && !!Zone.root.run;
private readonly schedulerTickApplyArgs = [{data: {'__scheduler_tick__': true}}];
private readonly afterTickSubscription = this.appRef.afterTick.subscribe(() => {
// If the scheduler isn't running a tick but the application ticked, that means
// someone called ApplicationRef.tick manually. In this case, we should cancel
// any change detections that had been scheduled so we don't run an extra one.
if (!this.runningTick) {
this.cleanup();
}
});
private readonly subscriptions = new Subscription();

private cancelScheduledCallback: null|(() => void) = null;
private shouldRefreshViews = false;
private pendingRenderTaskId: number|null = null;
private useMicrotaskScheduler = false;
runningTick = false;

constructor() {
this.subscriptions.add(this.appRef.afterTick.subscribe(() => {
// If the scheduler isn't running a tick but the application ticked, that means
// someone called ApplicationRef.tick manually. In this case, we should cancel
// any change detections that had been scheduled so we don't run an extra one.
if (!this.runningTick) {
this.cleanup();
}
}));
this.subscriptions.add(this.ngZone.onUnstable.subscribe(() => {
// If the zone becomes unstable when we're not running tick (this happens from the zone.run),
// we should cancel any scheduled change detection here because at this point we
// know that the zone will stabilize at some point and run change detection itself.
if (!this.runningTick) {
this.cleanup();
}
}));

// TODO(atscott): These conditions will need to change when zoneless is the default
// Instead, they should flip to checking if ZoneJS scheduling is provided
this.disableScheduling ||= !this.zonelessEnabled &&
Expand Down Expand Up @@ -196,7 +209,7 @@ export class ChangeDetectionSchedulerImpl implements ChangeDetectionScheduler {
}

ngOnDestroy() {
this.afterTickSubscription.unsubscribe();
this.subscriptions.unsubscribe();
this.cleanup();
}

Expand Down
31 changes: 31 additions & 0 deletions packages/core/test/change_detection_scheduler_spec.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -767,4 +767,35 @@ describe('Angular with scheduler and ZoneJS', () => {
await fixture.whenStable();
expect(ticks).toBe(1);
});

it('does not cause double change detection with run coalescing when both schedulers are notified',
async () => {
if (isNode) {
return;
}

TestBed.configureTestingModule({
providers:
[provideZoneChangeDetection({runCoalescing: true, ignoreChangesOutsideZone: false})]
});
@Component({template: '{{thing()}}', standalone: true})
class App {
thing = signal('initial');
}
const fixture = TestBed.createComponent(App);
await fixture.whenStable();

let ticks = 0;
TestBed.runInInjectionContext(() => {
afterRender(() => {
ticks++;
});
});
// notifies the zoneless scheduler
fixture.componentInstance.thing.set('new');
// notifies the zone scheduler
TestBed.inject(NgZone).run(() => {});
await fixture.whenStable();
expect(ticks).toBe(1);
});
});