it('rejects question-mark-prefixed relative commands with an explicit empty root segment', async () => {
    @Component({
      template: `<a [routerLink]="['?' + someVar, someId]">commands</a>`,
      imports: [RouterLink],
    })
    class WithLink {
      readonly someVar = 'search';
      readonly someId = '123';
    }

    const snapshot: any = {
      url: [new UrlSegment('', {})],
      children: [],
      outlet: PRIMARY_OUTLET,
    };
    snapshot.root = snapshot;
    TestBed.configureTestingModule({
      providers: [
        provideRouter([{path: '', component: WithLink}]),
        {provide: ActivatedRoute, useValue: {snapshot}},
      ],
    });
    const fixture = TestBed.createComponent(WithLink);

    await expectAsync(fixture.whenStable()).toBeRejectedWithError(
      /NG04019: Cannot serialize a UrlTree that would produce a protocol-relative URL/,
    );
  });

it("can fail after a redirect promotes the link's trailing empty segment", async () => {
  @Component({
    template: `<a [routerLink]="['/' + someVar, someId]">commands</a>`,
    imports: [RouterLink],
  })
  class WithLink {
    readonly someVar = 'source';
    readonly someId = '';
  }

  @Component({template: ''})
  class Target {}

  TestBed.configureTestingModule({
    providers: [
      provideRouter([
        {path: '', pathMatch: 'full', component: WithLink},
        {path: 'source/:id', redirectTo: '/:id/target'},
        {path: '**', component: Target},
      ]),
    ],
  });

  const harness = await RouterTestingHarness.create('/');
  const anchor = harness.fixture.nativeElement.querySelector('a');

  // RouterLink itself produces a valid href.
  expect(anchor.getAttribute('href')).toBe('/source/');

  anchor.click();

  // The redirect promotes the empty :id and produces //target.
  await expectAsync(harness.fixture.whenStable()).toBeRejectedWithError(
    /NG04019: Cannot serialize a UrlTree that would produce a protocol-relative URL/,
  );
});

// Short variant
it('rejects an empty dynamic segment passed separately after the root command', async () => {
  @Component({
    template: `<a [routerLink]="['/', someVar, someId]">commands</a>`,
    imports: [RouterLink],
  })
  class WithLink {
    readonly someVar = '';
    readonly someId = '123';
  }

  TestBed.configureTestingModule({
    providers: [provideRouter([])],
  });

  const fixture = TestBed.createComponent(WithLink);

  await expectAsync(fixture.whenStable()).toBeRejectedWithError(
    /NG04019: Cannot serialize a UrlTree that would produce a protocol-relative URL/,
  );
});