@ProvidedBy doesn't work with enums

[gissuebot]

From limpbizkit on December 29, 2008 15:22:36

Thierry reports that @ProvidedBy doesn't work with enums. @ImplementedBy and enums doesn't
make sense, but this should definitely work.

Original issue: http://code.google.com/p/google-guice/issues/detail?id=295

[gissuebot]

From limpbizkit on April 26, 2009 14:46:04

(No comment was entered for this change.)

Labels: Priority-Low

[gissuebot]

From Maaartinus on March 04, 2011 16:20:51

This bug is over 2 years old, and AFAIK, the fix is a (less then) one-liner. There's a (possibly useless) test in InjectorImpl.createUninitializedBinding commented as "Don't try to inject arrays, or enums." - the probable reason for this is the wrong assumption that it makes no sense at all. The test only makes it fail a bit faster in case of something is wrong, and may IMHO be completely omitted. Could you please do it?

Attachment: gist
   0001-Make-ProvidedBy-work-with-enums-issue-295.patch

[gissuebot]

From rkapsi on September 25, 2011 12:01:48

Here's an use-case if you need one. I have an enum that defines the various runtime environments of my software and I use the system properties to define the environment at startup. I'm currently using Module but @ProvidedBy would be a much cleaner approach.

@ProvidedBy(EnvProvider.class)
public enum Env {
  DEVELOPMENT,STAGING,PRODUCTION;

  public static Env environment() {
    String env = System.getProperty("my.env");
    if (env != null) {
      return Env.valueOf(env.toUpperCase());
    }
    return DEVELOPMENT;
  }

  public static class EnvProvider implements Provider<Env> {
    public Env get() {
      return Env.environment();
    }
  }
}

[gissuebot]

From Maaartinus on December 16, 2013 01:38:40

I'd propose something like

public enum Env {
  @DefaultInstance DEVELOPMENT,
  STAGING,
  PRODUCTION;
}

but I can see that the Provider-based approach is much more general (and needs no new annotation). My use case is exactly the same. In a few days we can celebrate the 5th birthday of this bug.

[Maaartinus]

Yes, let's celebrate! And no, I don't mind talking to myself (as long it's not too often). My above proposal is actually a different syntax for

@ImplementedBy(Env.DEVELOPMENT)
public enum Env {
  DEVELOPMENT,
  STAGING,
  PRODUCTION;
}

So it looks like both @ImplementedBy and @ProvidedBy make sense for enums.

[sameb]

For @ImplementedBy, that looks like it's trying to provide a default value for Env. The better way to do that would be using the OptionalBinder with a default value.

I agree it makes sense for @ProvidedBy, though. Is the above patch still valid? If so, can you send a pull request with it?

[sameb]

Fixed in 1285790.

[Maaartinus]

For @ImplementedBy, that looks like it's trying to provide a default value for Env.

I see I was wrong as the argument of @ImplementedBy must be a class, so a different annotation would be needed.

The better way to do that would be using the OptionalBinder with a default value.

Sounds good, except in simple cases when I want it to work without any configuration. But @ProvidedBy solves it (although a bit verbosely).