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

[Daniel Holth]

On Thu, Jul 12, 2012 at 12:03 PM, Daniel Holth <dholth at gmail.com> wrote:
>> +1 To this.  I agree Setup-Requires and Provides-Extra are different
>> use cases and should both be added to the spec.  I think that filling
>> in these two missing features will benefit packaging in the long run.
>> If this idea gains some amount of acceptance I'm happy to work on an
>> implementation of the setup-requires end of things for packaging.
>
> One last addition, explicitly allow X- headers. IMO the technical
> purpose of each tag is solid. I would like to get this implemented by
> the end of July so that it can be used.

If there are no further comments, I will ask Benjamin Peterson to
merge this into python-peps this weekend.

To avoid NameError, distutils2 should define extra == None by default
until it supports extras (simply not installing any extra
dependencies), or markerlib should just be folded in. For markerlib's
Python 2.4 problem a fallback that doesn't require _ast is either the
current distutils2 marker implementation, or to evaluate empty markers
as True, and non-empty markers as False, so only installing
unconditional dependencies; I don't suppose many Python 2.4 users are
clamoring to adopt .dist-info & Metadata 1.2...

Thanks,

Daniel Holth