Re: [PATCH 1/2] build: Generalize 'package-with-explicit-python'.

[Federico Beffa <beffa@ieee.org>]

On Wed, Feb 8, 2017 at 8:09 PM, Ricardo Wurmus <rekado@elephly.net> wrote:
>
> Federico Beffa <beffa@ieee.org> writes:
>
>> Generalize the Python procedure to recursively replace compiler/interpreter.
>> From a8220b430d196e5bb079e23ac63b1acd16fdaaee Mon Sep 17 00:00:00 2001
>> From: Federico Beffa <beffa@fbengineering.ch>
>> Date: Wed, 8 Feb 2017 18:55:32 +0100
>> Subject: [PATCH 1/2] build: Generalize 'package-with-explicit-python'.
>>
>> * guix/build-system/python.scm (package-with-explicit-python): Remove it and
>>   replace it with the generalized procedure 'package-with-explicit-compiler'
>>   in the new file. (package-with-python2): Adapt it.
>> * guix/build-system/utils.scm: New file with the generalized procedure.
>> * Makefile.am (MODULES): Add new file.
>
> The goal here is to override packages in build system arguments, right?
> This is great and we really need something like this to make building
> package variants simpler.  (I ran into a problem that would be solved by
> this when I tried to build Perl modules for different variants of Perl.)

Hi Ricardo,

The goal is to exploit the compiler keyword argument of many
build-systems (such as #:python, #:haskell, ...) to pass the desired
compiler instead of the default one.

> Looking over the patch it feels inelegant to have a whitelist of
> permitted arguments, as in “compiler-keyword”.  We already have a
> procedure called “package-input-rewriting” that replaces any (explicit
> input-) package in the dependency graph with a different package.  What
> I like about that is that it is generic.  Is there a way we could extend
> it to include packages pulled in by the build system, e.g. by making it
> work at the level of bags?

The procedure was not written by me: 99% of it comes from the
python-build-system.  The only thing that I did is to replace the
hard-coded '#:python' keyword with a variable one such that it can be
used with some other build systems. This seemed to me as one step in
the right direction, but if you have a better idea then please go
ahead and write it.  I will not feel offended ;-)

Regards,
Fede