bug#22437: Fixing package-with-python2

[ludo@gnu.org (Ludovic Courtès)]

Efraim Flashner <efraim@flashner.co.il> skribis:

> On Wed, 03 Feb 2016 09:47:15 +0100
> ludo@gnu.org (Ludovic Courtès) wrote:

[...]

>> This will trigger rebuilds (but with an identical result) because in
>> manually-written variants we would use “python2-foo” as the label of
>> inputs, whereas the automatic transformations keeps the original
>> “python-foo” label.
>
> rebuilds python-foo and python2-foo, or just the python2- variants?

The latter.

>> What do people think?
>
> I like it. It keeps the logic in the build-system. In terms of a speed test
> when figuring out the build/dependancy graph, how does it affect the time of
> `guix graph python2-scipy python2-matplotlib`?

It might be slightly faster, but it’s already rather fast.  :-)

--8<---------------cut here---------------start------------->8---
$ time guix graph python2-scipy python2-matplotlib >/dev/null

real	0m0.664s
user	0m0.768s
sys	0m0.056s
--8<---------------cut here---------------end--------------->8---


[...]

>> Does that make sense?  Any takers?  (This can be done incrementally.)
>
> It fits our "one change per commit" policy, and if we don't start at the base
> of the pyramid we'll be modifying and then removing the special variants. I
> don't mind doing the conversion process.

OK.

> Thinking aloud, I think for the time being we should keep the
> python-setuptools that are already part of the python- variants where they
> are and save that for another time.

Agreed.

Thanks for your feedback!

Ludo’.