Does this Dagger subcomponent need an empty module in the parent component?

App.java

import dagger.BindsInstance;
import dagger.Component;
import dagger.Subcomponent;
import javax.inject.Inject;

final class App {
  private final Sub.Builder subBuilder;
  private final AppDependency appDependency;

  @Inject App(AppDependency appDependency, Sub.Builder subBuilder) {
    this.appDependency = appDependency;
    this.subBuilder = subBuilder;
  }

  @Component(modules = AppComponent.Module.class) interface AppComponent {
    App getApp();

    @Component.Builder interface Builder {
      @BindsInstance Builder appDependency(AppDependency appDependency);

      AppComponent build();
    }

    // TODO: How can we elide this module whose only job is to declare the subcomponent?
    @dagger.Module(subcomponents = Sub.class) abstract class Module {
    }
  }

  @Subcomponent interface Sub {
    SubDependency getSubDependency();

    @Subcomponent.Builder interface Builder {
      @BindsInstance Builder subDependency(SubDependency subDependency);

      Sub build();
    }
  }

  void run() {
    Sub sub = subBuilder.subDependency(new SubDependency()).build();
    System.out.println(appDependency);
    System.out.println(sub.getSubDependency());
  }

  public static void main(String[] args) {
    AppComponent appComponent = DaggerApp_AppComponent.builder().appDependency(new AppDependency())
        .build();
    App app = appComponent.getApp();
    app.run();
  }

  static final class AppDependency {
    @Override public String toString() {
      return "AppDependency{}";
    }
  }

  static final class SubDependency {
    @Override public String toString() {
      return "SubDependency{}";
    }
  }
}

Not sure if it will help for you, due to my experience level.

But have you looked into ContributesAndroidInjector?