## Summary
This PR modifies the resolver to treat the Python version as a package,
which allows for better error messages (since we no longer treat
incompatible packages as if they "don't exist at all").
There are a few tricky pieces here...
First, we need to track both the interpreter's Python version and the
_target_ Python version, because we support resolving for other versions
via `--python 3.7`.
Second, we allow using incompatible wheels during resolution, as long as
there's a compatible source distribution. So we still need to test for
`requires-python` compatibility when selecting distributions.
This could use more testing, but it feels like an area where `packse`
would be more productive than writing PyPI tests.
Closes https://github.com/astral-sh/puffin/issues/406.
I'm working off of @konstin's commit here to implement arbitrary unsat
test cases for the resolver.
The entirety of the resolver's io are two functions: Get the version map
for a package (PEP 440 version -> distribution) and get the metadata for
a distribution. A new trait `ResolverProvider` abstracts these two away and
allows replacing the real network requests e.g. with stored responses
(https://github.com/pradyunsg/pip-resolver-benchmarks/blob/main/scenarios/pyrax_198.json).
---------
Co-authored-by: konsti <konstin@mailbox.org>
## Summary
This is a refactor to address a TODO in the build context whereby we
aren't respecting the resolution options in recursive resolutions. Now,
the options are split out from the resolution _manifest_, and shared
across the build context tree.