From mboxrd@z Thu Jan  1 00:00:00 1970
From: Leo Famulari <leo@famulari.name>
Subject: Re: The art of guessing a packaged downgrade version of a package
Date: Fri, 1 Jan 2016 16:09:59 -0500
Message-ID: <20160101210959.GA11284@jasmine>
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To: swedebugia@riseup.net
Cc: guix-devel <guix-devel@gnu.org>

On Fri, Jan 01, 2016 at 09:35:40PM +0100, swedebugia@riseup.net wrote:
> (trying to get gnupg to work knowing that ludo runs some 2.0 version)
> ~/src/guix$ guix package -i gnupg:2.0.0 -r gnupg
> guix package: error: package `gnupg-2.1.10' lacks output `2.0.0'

Did you try `guix package -i gnupg-2.0.29`? That should put the 2.0
series gnupg in your profile. You can even specify just 'gnupg-2.0' and
Guix will pick the lastest available gnupg in the '2.0' series.

> 
> I would like to improve this command by making it either show me the valid
> outputs (and optionally choosing one of them to install) for this specific
> package OR hint me about running:
> guix package --show=gnupg

I see the value of hints, but never an interactive command as suggested
by a menu of valid outputs. Interactive commands break automation.

> ~$ guix package --show=gnupg
> name: gnupg
> version: 2.1.10
> outputs: out
> ...
> 
> name: gnupg
> version: 2.0.29
> outputs: out
> ...
> 
> name: gnupg
> version: 1.4.20
> outputs: out
> 
> to get the information I need.
> 
> I found the relevant code in:
> ../gnu/packages.scm:381:        (leave (_ "package `~a' lacks output
> `~a'~%")
> 
> To be able myself to improve this snippet I would have to learn a lot more
> Guile first. :p
> 
> Anybody care to help?
> 
> swedebugia
>