refactor(core): allow disabling checkNoChanges with zoneless (angular#57416)

Disabling `checkNoChanges` in `ComponentFixture.detectChanges` was an
error for the zoneless fixture since it was not yet working. This now
allows checkNoChanges to be disabled. This option isn't really
used/shouldn't be used by anyone except the FW so marked as a refactor.

PR Close angular#57416

Author: atscott

packages/core/test/component_fixture_spec.ts

@@ -563,4 +563,22 @@ describe('ComponentFixture with zoneless', () => {
     const fixture = TestBed.createComponent(App);
     await expectAsync(fixture.whenStable()).toBeRejected();
   });
+
+  it('can disable checkNoChanges', () => {
+    @Component({
+      template: '{{thing}}',
+      standalone: true,
+    })
+    class App {
+      thing = 1;
+      ngAfterViewChecked() {
+        ++this.thing;
+      }
+    }
+
+    const fixture = TestBed.createComponent(App);
+    expect(() => fixture.detectChanges(false /*checkNoChanges*/)).not.toThrow();
+    // still throws if checkNoChanges is not disabled
+    expect(() => fixture.detectChanges()).toThrowError(/ExpressionChanged/);
+  });
 });

packages/core/testing/src/component_fixture.ts

@@ -34,6 +34,7 @@ import {TestBedApplicationErrorHandler} from './application_error_handler';
 
 interface TestAppRef {
   externalTestViews: Set<ViewRef>;
+  skipCheckNoChangesForExternalTestViews: Set<ViewRef>;
 }
 
 /**
@@ -131,27 +132,27 @@ export class ComponentFixture<T> {
    * Trigger a change detection cycle for the component.
    */
   detectChanges(checkNoChanges = true): void {
-    if (this.zonelessEnabled && !checkNoChanges) {
-      throw new Error(
-        'Cannot disable `checkNoChanges` in this configuration. ' +
-          'Use `fixture.componentRef.hostView.changeDetectorRef.detectChanges()` instead.',
-      );
-    }
-
     this._effectRunner.flush();
-    if (this.zonelessEnabled) {
-      this._appRef.tick();
-    } else {
-      // Run the change detection inside the NgZone so that any async tasks as part of the change
-      // detection are captured by the zone and can be waited for in isStable.
-      // Run any effects that were created/dirtied during change detection. Such effects might become
-      // dirty in response to input signals changing.
-      this._ngZone.run(() => {
-        this.changeDetectorRef.detectChanges();
-        if (checkNoChanges) {
+    const originalCheckNoChanges = this.componentRef.changeDetectorRef.checkNoChanges;
+    try {
+      if (!checkNoChanges) {
+        this.componentRef.changeDetectorRef.checkNoChanges = () => {};
+      }
+
+      if (this.zonelessEnabled) {
+        this._appRef.tick();
+      } else {
+        // Run the change detection inside the NgZone so that any async tasks as part of the change
+        // detection are captured by the zone and can be waited for in isStable.
+        // Run any effects that were created/dirtied during change detection. Such effects might become
+        // dirty in response to input signals changing.
+        this._ngZone.run(() => {
+          this.changeDetectorRef.detectChanges();
           this.checkNoChanges();
-        }
-      });
+        });
+      }
+    } finally {
+      this.componentRef.changeDetectorRef.checkNoChanges = originalCheckNoChanges;
     }
     this._effectRunner.flush();
   }