Tree-shakable providers scoped to the root injector don't get registered #1417

What are tree-shakable providers?

Angular 6 introduced a new way to register providers in order to make them tree-shakable. That gives Angular the ability to remove services that are not used in the application from the final output.
To create a tree-shakable provider you need to specify the injector which injects a service in the metadata of that service. For example:

@Injectable({
  providedIn: 'root',
})
export class Service {
}

Setting the value to root ensures that the service is scoped to the root injector.

Issue

The tree-shakable providers scoped to the root injector (the above example) don't get registered in NativeScript, which results in the following error:

Error: NullInjectorError: No provider for Service!

Solution

The NativeScriptModule should be marked as root. We can do that by providing the APP_ROOT token in the metadata of that module.

Demo

https://play.nativescript.org/?template=play-ng&id=tCY7bL