Same injects both in subcomponent and parent component with same dependencies type.

Suppose we have next Dagger2 configuration:

@Component(modules = ModuleA.class)
public interface ComponentA {
    void inject(MainActivity activity);
    ComponentB plus();
}

@Module
public class ModuleA {
    @Provides
    public String string() {
        return "A";
    }
}


@Subcomponent(modules = ModuleB.class)
public interface ComponentB {
    void inject(MainActivity activity);
}

@Module
public class ModuleB {
    @Provides
    public String string() {
        return "B";
    }
}


public class MainActivity extends AppCompatActivity {

    @Inject
    String string;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        DaggerComponentA.create().plus().inject(this);

        System.out.println(string); //A
    }
}

Wouldn’t it be better if Dagger2 threw an exception instead of injection “A”? If we remove inject from ComponentA the code will not compile, because “String is bound multiple times”. Is it a bug or a feature?

P.S. Full code available here

[ronshapiro]

This is now correctly reported as an error.

[naturalwarren]

At the moment I’m not aware of any updates; fixing this required a large change to how dependencies are resolved.