[Distutils] Adding Provides-Extra as an edit to PEP 345

[Daniel Holth]

On Fri, Jul 6, 2012 at 11:01 AM, Éric Araujo <merwok at netwok.org> wrote:
>> Hopefully this will be a more useful spec.
>
> Thanks for the proposal, but it is not really a spec.  You’re suggesting
> name and syntax for a new field, but you don’t describe what it means and
> what it is used for.  From what I understand, the goal is similar to build
> dependencies and optional dependencies in systems like Debian’s dpkg; for
> the build dependencies, there were multiple threads about adding
> Setup-Requires-Dist (like setuptools’ setup_requires) and Test-Requires-Dist
> (like tests_require, or whatever the spelling is—I always get it wrong :),
> for which we were near to agreement.  See
> https://groups.google.com/forum/?fromgroups#!searchin/the-fellowship-of-the-packaging/setup-requires/the-fellowship-of-the-packaging/KVsDQawfEno/M-ODKx9Ne5YJ
> and
> https://groups.google.com/forum/?fromgroups#!searchin/the-fellowship-of-the-packaging/setup-requires/the-fellowship-of-the-packaging/yTsRLtl6eoE/fVGb4t2zm68J

It is exactly the same as setuptools' "extras" feature, and I didn't
quote the entire edit on-list. Also, there is a reference
implementation at https://bitbucket.org/dholth/distribute/ in the
DistInfoDistribution class.

The 'test' and 'doc' reserved names are not an essential part of the
Provides-Extra feature. Provides-Extra: is primarily for optional
run-time (not build-time) dependencies.

>> This begs for parenthesis in environment markers, something that is
>> easy to do by compiling markers to Python functions using the ast as
>> `markerlib` does.
>
> distutils2 supports Python 2.5, which has _ast but not ast IIRC.  If you
> have other suggestions for improvements like this please open bug reports
> though!  Feedback and patches are welcome.

markerlib is not required for Provides-Extra: It was just a convenient
way to add the additional 'extra' variable name to environment
markers.

markerlib uses a few helpers from ast.py. Python 2.5 support would
mean copying those helpers into markerlib.