Subject: Re: bug#52684: [BUG] Multiple Packages Failing to Build

From: Christopher Rodriguez <[email-masked]>
Date: Wed, 22 Dec 2021 16:57:52 -0500

On 12/22/21 3:50 PM, Maxime Devos wrote:

> python-build-system doesn't GUIX_PYTHONPATH, because that's the job of
> the native-search-paths of python. When a python library is being
> built, GUIX_PYTHONPATH is set because the library has python among its
> (implicit) inputs. The same holds for profiles: if python and package
> containing a lib/pythonVERSION/site-packages are in the same profile,
> then GUIX_PYTHONPATH is set in that profile.

I think this is the main issue, here. Installing 'beets' in a profile 
doesn't install python, and therefore it doesn't trigger the 
GUIX_PYTHONPATH variable. 'beets' still runs because it is referencing a 
python in the store, not in the profile, but it can't find plugins that 
aren't installed in the core package because the GUIX_PYTHONPATH 
environment variable is not being set to point to the directory in the 
profile where they are symlinked. Setting this manually to point to 
site-packages immediately solves the issue.

> There's a reason why we don't ‘just propagate’ like in classical
> distros: what if the user installs a version of python incompatible
> with the version used by beets?
> 
> To avoid such incompatibilities (and other problems), the interpreter
> of binaries (and the load path) is hard-coded at built time.
> 
> Also, if this is about plugins: adding GUIX_PYTHONPATH to beets'
> native-search-paths should work (the wrapper uses 'prefix', not '=').

This is ingenious, and one of the reasons I really love using GNU/Guix. 
Such a clever fix to allow the user to really customize their system, 
and use their computer the way they want.

The more we discuss this, the more it seems to me that there should 
indeed be an environment variable specific to beets, to point to where 
the plugins should be linked.

We don't want to bring in python and force a user to decide between 
beets and their version of python, but (due to the way the python 
plugins are loaded in 'beets') we need to add a pointer to the 
site-packages of the python beets is using to run.

Are variables that point to places in the profile allowed? Or do they 
have to only point to the store? That would solve the chicken and egg 
problem here, where we can't hardcode the directory of the plugin into 
'beets' because the plugin is installed afterwards…

--

Christopher Rodriguez