Guice private parent Module expose binding to child modules

Question

I have following Guice private module dependency tree:

public class FooModule extends PrivateModule {
    @Override
    protected void configure() {
      install(new BarModule());
      bind(Person.class);
      expose(Person.class);
    }
}

public class BarModule extends PrivateModule {
    @Override
    protected void configure() {
      install(new LifeImplModule());
      bind(Animal.class);
      expose(Animal.class);
    }
}

public class LifeImplModule extends PrivateModule {
    @Override
    protected void configure() {
      bind(Life.class).toInstance(new LifeImpl());
      expose(Life.class);
    }
}

public class Animal {
    @Inject
    public Animal(Life life) {
      //
    }
}

public class Person {
    @Inject
    public Person(Life life) {
       //
    }
}

Now when I do Guice.createInjector(new FooModule()).getInstance(Person.class) - it fails since it doesn't recognize binding for Life.class whereas Guice.createInjector(new FooModule()).getInstance(Animal.class) works since it has binding for Life via BarModule.

How do I go about solving this issue? I tried moving
install(new LifeImplModule()); to FooModule() but then Animal.class doesn't work, while Person.class does.

Could anybody explain how does Guice private module work in terms of inheriting bindings? Is install(LifeImplModule()) in FooModule not work for both Person.class and child module BarModule()?

Answer 1

Since BarModule is a private module, any modules installed inside it won't be available externally.
That's why

install(new LifeImplModule());

doesn't grant access to Life binding for FooModule. You can solve it by explicitly exposing Life from BarModule

install(new LifeImplModule());
expose(Life.class);