Respect python-requires in offline mode (--find-link --no-index)

One way (and before the rewrite release the only way) to bootstrap a virtual environment in an offline environment is to point pip to some bundled wheels via the --find-links parameter. The problem is that if this folder contains both wheels that support the target environment and wheels that don’t (e.g. with setuptools 45 dropping python 2), pip does not pick the last supported version of a package, but instead picks the highest version, and then fails at install time.

Triggered by https://github.com/pypa/virtualenv/issues/1496.

[pfmoore]

I don’t think that fixes the wider problem

It doesn’t. And it doesn’t make any difference when a sdist is available, as the fact that the tag doesn’t cover py2 just means that the sdist will be used (at which point Python-Requires kicks in). But none of that is IMO any reason not to tag the wheel correctly.

IMO, Python-Requires should be handled by the resolver, as this issue suggests, so that only versions that support the Python version being used are considered. But doing so has a cost, as checking Python-Requires can need anything up to a full build. So having as many other indications that a file isn’t relevant for the current interpreter is still useful.

[pfmoore]

@sbidoul Good idea, As long as there’s no local sdist, and the PyPI files have the correct data-requires-python tag (which it does) then this should be a reasonable fix.