bug#23874: duplicates in manifests are “installed” more than once

[Ludovic Courtès]

Hi!

Ricardo Wurmus <address@hidden> skribis:

> No conflicts are reported, so no harm is done, but seemingly having the
> very same package more than once in a profile might be confusing.
>
> Should Guix issue a warning when the same variable is referenced more
> than once (I don’t like this because there really is no problem), or
> should Guix delete duplicates from the list before creating a profile
> generation?

I think it should both delete duplicates, and then error out when two or
more packages with the same name remain.  Further, this should take into
account propagated inputs.

I think this is a pretty radical change, though, and I wonder about the
amount of breakage it would create.  For instance, it means that one
could create a profile containing both magit-referring-to-git-2.8 and
git-2.9, or emms-referring-to-vorbis-tools-1.0 and vorbis-tools-2.0.
Concretely, that means one will no longer be able to upgrade magit
without also upgrading git, for instance (assuming they live in the same
profile.)

WDYT?

Thanks,
Ludo’.