Re: [PATCH] gnu: Add Python 3.

[ludo@gnu.org (Ludovic Courtès)]

Andreas Enge <andreas@enge.fr> skribis:

> Am Mittwoch, 28. August 2013 schrieb Ludovic Courtès:
>> > +(define-public python3
>> 
>> Nice that it works without any modifications.  Please push.  (I think
>> Andreas wanted to discuss the naming convention for Python packages, but
>> I think adding Python 3 doesn’t cause any problems.)
>
> Only a little ;-)
>
> I would rename
>    (define-public python
> to
>    (define-public python-2
>
> and add
>    (define-public python
> for python version 3 (compare libjpeg for version 9 and libjpeg-8).

What about having 3 variables: python-3, python-2, and python; ‘python’
would point to whichever is the default.

For GCC and Guile we don’t even have the version-less variable name.
Instead ‘gnu-build-system’ explicitly refers to the one we want.

Anyway, I don’t think this should block this patch.

> Then all packages relying on python will be recompiled with the newest 
> version. If this poses problems, we could modify the input to python-2.
>
> Rationale: We would like to package the newest versions and give their 
> variables the default names. If for compatibility problems, we need an 
> older version, the corresponding variable should get a suffix. (While the 
> NAME field of a package should be the default name in all cases.)

Sounds like the right approach for a start.

However, some packages will work with both versions, while others will
be 2-only or 3-only.  We’ll most likely build both variants for those
that work with both 2 and 3, for instance because there’s both a 2-only
and a 3-only package that depends on them.  Thus, eventually, there may
be a need for a procedure that rewrites a package to explicitly depend
on a given package version (similar to ‘rewritten-inputs’ in
build-system/gnu.scm).

Ludo’.