[Python-Dev] [Distutils] PEP 426 is now the draft spec for distribution metadata 2.0

[Antoine Pitrou]

Le Tue, 19 Feb 2013 10:24:15 +0000,
Paul Moore <p.f.moore at gmail.com> a écrit :
> On Tuesday, 19 February 2013, M.-A. Lemburg wrote:
> 
> >
> > The only tool in wide spread use that understands part of the 1.2
> > data is setuptools/distribute, but it can only understand the
> > Requires-Dist field of that version of the spec (only because the
> > 1.1 Requires field was deprecated) and interprets a Provides-Extra
> > field which isn't even standard. All other 1.2 fields are ignored.
> > setuptools/distribute still writes 1.1 meta-data.
> >
> > I've never seen environment markers being used or supported
> > in the wild.
> >
> > I'm not against modernizing the format, but given that version 1.2
> > has been out for around 8 years now, without much following,
> > I think we need to make the implementation bit a requirement
> > before accepting the PEP.
> >
> 
> The wheel project uses metadata 2.0 and environment markers - indeed,
> the PEP was written to formalise what wheel was implementing
> (specifically so that pip was happy to incorporate support).

I'm unsure what this means. Does the "wheel project" (I thought wheel
was a format? is it also a project?) reimplement its own wheel of
metadata parsing and generating?

> I agree that standard library support would be good, either via
> Distutils or by incorporating distlib, but I don't think it is
> essential for acceptance.

I think Marc-André is right that the acceptability of the standard
should be judged on the availability of (preferably standard)
implementations. If the standard isn't implemented, then perhaps it
means it's too ambitious / too complex / victim of the second-system
effect.

So I kind of agree with him the PEP shouldn't be accepted until there's
a decent patch pending for the stdlib. That's not a judgement on the
PEP's quality. Just an advice to remain cautious, especially if the
previous metadata version already enjoys a very poor adoption rate.

By the way, pip may be nice, but it's still a third-party tool, and
perhaps not even as widespread as distribute / setuptools.

Regards

Antoine.