refactor(core): Provide scheduler for use and coordination with zone change detection

[atscott]

This commit makes the zoneless scheduler (privately) available to applications that have ZoneJS-based change detection. This would catch any changes of interest (signal updates, markForCheck calls, attaching Dirty views) that happen outside the Angular Zone.

See #53844 for additional information about why this is important. More details to come in the a future commit that makes this a public option.

[eneajaho]

This is 🚀

Because this opens up the possibility to have zoneless and not zoneless parts of an application.

Will this work ?

@Directive({
  selector: 'zoneless',
  standalone: true
})
export class Zoneless {
  vcRef = inject(ViewContainerRef);
  tplRef = inject(TemplateRef);
  ngZone = inject(NgZone);

  ngOnInit() {
    this.ngZone.runOutsideAngular(() => {
       this.vcRef.createEmbeddedView(this.tplRef);
    });
  }
}

and apply it on some router-outlet

// main-layout.component.html

<header />
<router-outlet  *zoneless />
<footer />

[atscott]

Because this opens up the possibility to have zoneless and not zoneless parts of an application.

Will this work ?

Yes and no. ZoneJS still patches Promise (and many other APIs) globally so you'd really need to have a particular portion of the application operate in an isolated zone so it truly doesn't contribute to the main app's zone.

edit: You'd probably see things working somewhat as expected for a bit because create mode would create all the handlers outside the zone so all their callbacks would execute outside the zone. But change detection still runs inside NgZone.run so as soon as something in that view is created as part of change detection (i.e. and @if block with another listener), that would get created inside the Angular zone.

edit 2: example

[eneajaho]

But change detection still runs inside NgZone.run so as soon as something in that view is created as part of change detection (i.e. and @if block with another listener), that would get created inside the Angular zone.

And that is supposed to change if Angular goes zoneless by default, right?

[atscott]

But change detection still runs inside NgZone.run so as soon as something in that view is created as part of change detection (i.e. and @if block with another listener), that would get created inside the Angular zone.

And that is supposed to change if Angular goes zoneless by default, right?

Change detection will always run inside ngZone.run but this doesn't change the execution zone in "zoneless" which uses NoopNgZone

[atscott]

caretaker note: This will require fixing the MfW implementation, as seen in cl/619562101

[dylhunn]

This PR was merged into the repository by commit 80f96e7.

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