Re: Fixing package-with-python2 (was: Package transformations)

[Efraim Flashner <efraim@flashner.co.il>]

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On Mon, 1 Feb 2016 08:49:10 -0500
"Thompson, David" <dthompson2@worcester.edu> wrote:

> On Mon, Feb 1, 2016 at 8:06 AM, Efraim Flashner <efraim@flashner.co.il> wrote:
> 
> > I looked over the commit but not deeply enough yet, would it be possible to
> > use some of the logic in this to fix the package-with-python2 issue?  
> 
> Here's a potential solution for 'package-with-python2': module
> introspection.  AIUI, the issue is that some Python 2 packages need
> extra manual tweaking, but 'package-with-python2' creates package
> variants without these tweaks. Our algorithm could look up
> 'python2-foo' in (gnu packages python) and use that package object, if
> it exists.  This would stop the recursive transformation for that
> branch of the dependency graph and allow us to tweak Python 2 variants
> as needed without fear.

Not all of our python packages are in python.scm. Currently in
guix/build-system/python.scm we have:

(define package-with-python2
  ;; Note: delay call to 'default-python2' until after the 'arguments' field
  ;; of packages is accessed to avoid a circular dependency when evaluating
  ;; the top-level of (gnu packages python).
  (package-with-explicit-python (delay (default-python2))
                                "python-" "python2-"))

Excuse the code, but I think we're looking for something like:

(define package-with-python2
  (if (exists? python2-foo)
    (python2-foo)
    (package-with-explicit-python (delay (default-python2))
                                  "python-" "python2-"))

> Also, somewhat unrelated, package-with-python2 could add setuptools as
> an input to these packages so we can remove all the unnecessary usage
> of it in Python 3 packages.
> 
> Thoughts?

That's something I was thinking of.

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Efraim Flashner   <efraim@flashner.co.il>   אפרים פלשנר
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