[9.0.0-rc.9] `CdkConnectedOverlay.backdropClick` events do not instigate change detection in `OnPush`

[benelliott]

Reproduction

See this repository as the StackBlitz template is not configured for v9 RC: https://github.com/benelliott/repro-cdk-overlay

Expected Behavior

What behavior were you expecting to see?

CdkConnectedOverlay.backdropClick events should be emitted within the Angular zone so that they are picked up by ChangeDetectionStrategy.OnPush.

Actual Behavior

Setting a value in a component based on the backdropClick event causes no changes under OnPush without a manual call to ChangeDetectorRef.detectChanges.

I think this is because in https://github.com/angular/components/blob/master/src/cdk/overlay/overlay-directives.ts#L380 the backdropClick.emit call needs to be run inside NgZone.run.

    if (this.hasBackdrop) {
      this._backdropSubscription = this._overlayRef.backdropClick().subscribe(event => {
        this.backdropClick.emit(event);
      });
    } else {
      this._backdropSubscription.unsubscribe();
    }

For some reason, this didn't cause issues under Angular/CDK v8 but it causes issues in Ivy, presumably due to internal changes in Ivy's change detector.

Environment

• Angular: 9.0.0-rc.14
• CDK/Material: 9.0.0-rc.9
• Browser(s): Chrome 79
• Operating System (e.g. Windows, macOS, Ubuntu): Windows 10

[crisbeto]

I'm not sure that the cause is the events being emitted outside the NgZone, because adding a console.log(NgZone.isInAngularZone()) in the handler logs true.

[benelliott]

Oops, sorry.

[Vizer]

Same issue if parent component has OnPush strategy

Angular: 9.0.2
CDK/Material: 9.1.0

[j2L4e]

This seems to be a more general problem. When you press the escape key, the overlay detaches, but the detach event doesn't trigger change detection as well.
Everything's working fine, when you cdr.markForCheck() in the handler.

https://github.com/angular/components/blob/master/src/cdk/overlay/overlay-directives.ts#L287

[visurel]

Issue still appearing with:

Angular: 9.1.9
CDK/Material: 9.2.4