Add pylock select function

[sbidoul]

This is WIP. Main missing part is handling of dependency groups and extras. And tests of course.

Comments are from PEP 751 Installation section.

closes #1087

[sbidoul]

/cc @brettcannon

[sbidoul]

@brettcannon why is it an error if a package requires-python is not satisfied? Should it not be skipped in that case?

[brettcannon]

That's for when https://packaging.python.org/en/latest/specifications/pylock-toml/#requires-python has been satisfied but somehow a specific package claims otherwise. When I wrote that I'm sure my brain was assuming requires-python would be set if packages.requires-python was set.

[sbidoul]

Except for the wheel file name discovery and validation mechanism (waiting for #1095) this should be complete and ready for review.

[sbidoul]

I tweaked the requires-python checks. Awaiting maintainers input on #1110 (comment) to finalize this.

[brettcannon]

@sbidoul is there some other PR you want to see merged, or are you ready for me to merge this?

[sbidoul]

@sbidoul is there some other PR you want to see merged, or are you ready for me to merge this?

@brettcannon as you prefer. If #1110 is merged first I'll update this one. If this one is merged first then I'll do another PR to use the selector when #1110 is merged.

[brettcannon]

@sbidoul I just merged @1110 .

[sbidoul]

And I integrated the compatible tags selector.

In 9f20a3c I relaxed the typing of create_compatible_tags_selector a bit to accept an Iterable instead of a Collection.

So all is done and clean here, I think. The only bits that I don't like are the type casts around Environment, but I couldn't find a way to please mypy.

[sbidoul]

And a test had to be updated following the stricter validation in #1114.

[brettcannon]

@sbidoul thanks so much for working on this! Hopefully this helps unblock pip from installing from a lock file.

[sbidoul]

That was fun. I'll now see what I can do in pip. That might be a bit more hairy.