Misleading error message with child injector

If you have a child injector and ask the parent injector a value for a binding defined in the child, you get an “It was already configured on one or more child injectors” error.

It would be better to say “No implementation for … was bound, although it is configured in a child injector”.

Here’s a sample code:

import com.google.inject.AbstractModule;
import com.google.inject.Guice;
import com.google.inject.Injector;

public class GuiceBug {

    public static void main(String[] args) {
        Injector i1 = Guice.createInjector();
        Injector i2 = i1.createChildInjector(
                new AbstractModule() {
                        @Override
                        protected void configure() {
                            bind(IStuff.class).to(Stuff.class);
                        }
                    });
        i1.getInstance(IStuff.class);
    }

    static interface IStuff {}

    static class Stuff implements IStuff {}
}

Exception in thread "main" com.google.inject.ConfigurationException: Guice configuration errors:

1) Unable to create binding for org.enercoop.test.GuiceBug$IStuff. It was already configured on one or more child injectors or private modules
    bound at org.enercoop.test.GuiceBug$1.configure(GuiceBug.java:15)
  If it was in a PrivateModule, did you forget to expose the binding?
  while locating org.enercoop.test.GuiceBug$IStuff

1 error
    at com.google.inject.internal.InjectorImpl.getProvider(InjectorImpl.java:1004)
    at com.google.inject.internal.InjectorImpl.getProvider(InjectorImpl.java:961)
    at com.google.inject.internal.InjectorImpl.getInstance(InjectorImpl.java:1013)
    at GuiceBug.main(GuiceBug.java:18)

[prdoyle]

I can’t help but think @laurentmartelli was right about this error.

• With my bind call, I get this error
• If I comment out my bind call, I get “No implementation for … was bound”

How can I have too many bindings, then remove one binding, and then not have enough?

[matveyshishovimanage]

It was confusing for me as well, googling this discussion turned out the fastest way to find the actual cause, so the message could just as well have a link to this discussion.