Child components are not correctly mocked with standalone on angular 19+

[cxing350]

When testing a component that consumes other components from a library that is compiled against an older version of angular, the mocked components that shallow-render generates are not correctly marked with the standalone flag.

See the following setup:

Test:

describe('DraftAvailableComponent', () => {
  let shallow: Shallow<DraftAvailableComponent>;

  beforeEach(() => {
    shallow = new Shallow(DraftAvailableComponent, DraftsModule).mockPipe(LanguagePipe, (key: string) => key);
  });

  it('should init DraftAvailableComponent', async () => {
    const { instance } = await shallow.render();
    expect(instance).toBeDefined();
  });

  it('display DraftAvailableComponent', async () => {
    const { instance, find } = await shallow.render();
    expect(instance).toBeDefined();
    expect(find('.draft-desc').nativeElement.textContent).toContain('mss.DRAFT_AVAILABLE_MESSAGE');
    expect(find('.continue-draft').nativeElement.textContent).toContain('mss.CONTINUE_DRAFT');
    expect(find('.new-action').nativeElement.textContent).toContain('mss.NEW_ACTION ');
  });
});

Module:

@NgModule({
  imports: [CommonModule, MyAdpCommonModule, SynergButtonModule, SynergIconModule, SynergModalModule],
  declarations: [DraftAvailableComponent, DraftSavedModalComponent],
  exports: [DraftAvailableComponent, DraftSavedModalComponent]
})
export class DraftsModule {}

In this example the Synerg modules originate from a library compiled against an older angular version and provide components to the component being tested. When running the tests this error occurs:

Unexpected "MockOfIconComponent" found in the "declarations" array of the "MockOfIconModule" NgModule, "MockOfIconComponent" is marked as standalone and can't be declared in any NgModule - did you intend to import it instead (by adding it to the "imports" array)?

As you can see, shallow-render is failing to tag the generated mock components with standalone: false