Re: program prepared with `guix pack` unusable by end users

[Maxim Cournoyer <maxim.cournoyer@gmail.com>]

Hello,

Wojtek Kosior <koszko@koszko.org> writes:

>> > IMHO yes, the pack output does not work as expected.  That's the
>> > definition of a bug.  
>> 
>> I disagree.  That Python gives precedence to USERSITE compared to
>> site-packages and GUIX_PYTHONPATH is by design, so that users can
>> override system provided libraries such as those by Guix.  It used to be
>> the other way around, and it caused all sort of problems such as
>> virtualenv not working as expected on Guix.

My memory failed me here; the past problems with Guix and virtualenv had
to do with us (ab)using PYTHONPATH, which would take precedence above
everything and not get reset by virtualenv, if I remember.

--8<---------------cut here---------------start------------->8---
$ . bin/activate
(venv) maxim@hurd /tmp/venv [env]$ python -m site
sys.path = [
    '/tmp/venv',
    '/gnu/store/bbakd2h7s4g62fymjmqpxgvlanp1ydny-python-3.9.9/lib/python39.zip',
    '/gnu/store/bbakd2h7s4g62fymjmqpxgvlanp1ydny-python-3.9.9/lib/python3.9',
    '/gnu/store/bbakd2h7s4g62fymjmqpxgvlanp1ydny-python-3.9.9/lib/python3.9/lib-dynload',
    '/tmp/venv/lib/python3.9/site-packages',
]
USER_BASE: '/home/maxim/.local' (exists)
USER_SITE: '/home/maxim/.local/lib/python3.9/site-packages' (doesn't exist)
ENABLE_USER_SITE: False
--8<---------------cut here---------------end--------------->8---

We can see that virtualenv disables loading libraries from USER_SITE
(ENABLE_USER_SITE: False).  We can also see that it puts its
site-packages directly on sys.path.

> Perhaps the best solution would be to
> * have Python interpreter itself give precedence to user site packages but
> * have user site disabled (or enabled with lower precedence) by default
>   for Python applications.
>
> Consider the creation of wrapper script for python programs as it is
> done now[1]. Is there currently any application that would behave
> incorrectly with PYTHONNOUSERSITE exported as 1 and
> `~/.local/lib/python<PYTHON-VERSION>/site-packages/` included in
> GUIX-PYTHONPATH after the other paths? If there is, perhaps it would be
> at least easier to make a workaround for this single application?

I agree that setting PYTHONNOUSERSITE to 1 in the wrapper of Python
commands to ensure no stray user-installed librairies from under
"~/.local/lib/python<PYTHON-VERSION>/site-packages/" clash with their
operation would make sense.

Note that this is an interoperability problem between 'guix' and 'pip',
for 'pip install x' users that end up filling their
"~/.local/lib/python<PYTHON-VERSION>/site-packages/" directory.  If you
'rm -rf ~/.local/lib/python*' and stick to use only Guix-provided
packages, they won't experience any issue.

-- 
Thanks,
Maxim