bug#19816: 'guix environment' always downloads all the outputs of dependencies

[ludo@gnu.org (Ludovic Courtès)]

ludo@gnu.org (Ludovic Courtès) skribis:

>From <http://debbugs.gnu.org/cgi/bugreport.cgi?bug=19641#16>:
>
> There’s another problem, though.  When a dependency is a multiple-output
> package, all its outputs are added to the environment, because
> ‘package->transitive-inputs’ discards the information of which output is
> needed.
>
> So for instance, both the ‘out’ and the ‘debug’ output of Coreutils end
> up being downloaded and added to the environment, even though only ‘out’
> is an input.
>
> Now, the problem is that ‘build-derivations’ can only build *all* the
> outputs of the given derivation.  This could be worked around either:
>
>   1. by creating a “sink” derivation, for instance with
>      ‘profile-derivation’, that could refer precisely to the output(s)
>      needed; not ideal.

David, I think you had started looking at doing exactly this.  Do you
have a preliminary patch you’d like to post?

I understand you may be busy preparing the Lisp Game Jam now and I
wouldn’t want to distract you from that.  ;-)  If you have something to
share, I’m happy to help start from there though (says the guy who sees
its ‘guix environment’ pointlessly downloading “debug” and “doc” outputs
again.)

Thanks,
Ludo’.