bdist_wheel predates marker support in setuptools and didn't support pulling markers from setup.py until 0.24.0, as noted in the wheel release notes. Older versions of bdist_wheel could read conditional requirements from a section in setup.cfg but could not translate markers from setuptools' requires.txt. Wheel's own source code demonstrates the syntax.
pip uses pkg_resources to parse dependencies for wheels and an old enough pip doesn't use wheels at all. On Wed, Oct 28, 2015 at 1:15 PM Marius Gedminas <mar...@gedmin.as> wrote: > Hi! > > pip 7 enables wheel caching by default, which is good. > > Wheel caching means you can't compute dynamic dependencies any more -- > i.e. things like > > setup( > ... > install_requires=[...] + (['enum34'] if sys.version_info[0] < 3 else > []), > ...) > > will cause problems. > > As far as I understand, you're supposed to use environment markers > instead. > > > Problem 1: where's the documentation? E.g. > https://python-packaging-user-guide.readthedocs.org/en/latest/distributing/ > has no mention of the word "marker". > > Try to google "setuptools environment marker" (and how is a user going > to discover the magical keyword they need to google is "environment > marker")? Try to find anything resembling documentation on the 1st > page. The best I could find was > http://docs.openstack.org/developer/pbr/#environment-markers which only > works if you use pbr. > > Even the spec ( > https://www.python.org/dev/peps/pep-0426/#environment-markers) > only shows how the markers are supposed to appear in the JSON metadata. > No clue is provided for poor writers of setup.py files. > > I somehow discovered the syntax once (I don't remember how -- most > likely kind people in #pypa spoon-fed me), but now I'm cargo-culting my > existing setup.py files that already use environment markers. > > > Problem 2: what are the minimum versions of the tools that your users > must have before you can rely on environment markers? > > - setuptools >= 0.7 ("Added experimental environment marker support") > > - wheel >= 0.24 (if you have wheel 0.23 or older, environment markers are > silently broken and have fun figuring out why: > https://github.com/pypa/pip/issues/2870). > > - does the pip version matter at all? I think not; please correct me if > I'm wrong. > > > Some official answers from the hard-working PyPA visionaries would be > welcome. > > Marius Gedminas > -- > I once held a little hand > That made my sad heart sing. > Twas the loveliest hand I'd ever held, > Four Aces and a King > _______________________________________________ > Distutils-SIG maillist - Distutils-SIG@python.org > https://mail.python.org/mailman/listinfo/distutils-sig >
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