On 6 Mar 2013 00:59, "PJ Eby" <p...@telecommunity.com> wrote: > > On Mon, Mar 4, 2013 at 3:20 PM, Paul Moore <p.f.mo...@gmail.com> wrote: > > On 4 March 2013 20:00, Daniel Holth <dho...@gmail.com> wrote: > >> On Mon, Mar 4, 2013 at 2:41 PM, Paul Moore <p.f.mo...@gmail.com> wrote: > >>> In thinking about how virtualenv would describe the packages it wants > >>> to preload in PEP 426 metadata form, it occurred to me that there are > >>> scenarios with setuptools and distribute where it's not obvious how to > >>> state the requirement you want. Specifically, if you want to install > >>> setuptools if it is present, but if not fall back to distribute (for > >>> example, if you have a local package repository and no access to PyPI, > >>> but setuptools may or may not be present). > > [...] > >> > >> We do have Provides-Dist, although the best way to implement it is an > >> open question. > > > > Good point. So distribute would have "Provides-Dist: setuptools" and I > > could just require setuptools. Given that none of this is supported > > yet, I'm happy that the spec covers this case, but still need to work > > around it for the immediate future. > > Provides-Dist doesn't actually work for most of the use cases for > alternates, though. For example, if a package that wants to require > one of the various mysql adapters, it doesn't make any sense for the > mysql packages to declare that they provide each other. ;-)
The adapter developers just need to agree on a virtual provides they will all publish. Of course, that won't be effective without an entry points extension to get the adapters loaded in a consistent fashion. Still, one step at a time :) Cheers, Nick. > _______________________________________________ > Distutils-SIG maillist - Distutils-SIG@python.org > http://mail.python.org/mailman/listinfo/distutils-sig
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