Support Metadata Version 2.2

[uranusjr]

What's the problem this feature will solve?
Since PEP 643 is accepted, PyPI should start accepting Metadata 2.2 distributions. See PyO3/maturin#564.

Describe the solution you'd like
Allow Metadata-Version: 2.2 to pass the legacy upload endpoint’s form validation, and validate the corresponding Dynamic field.

The latter part could be a bit tricky since Dynamic is not allowed for wheels. Not sure how it could be best handled (I don’t have much experience with WTForm).

Additional context
https://www.python.org/dev/peps/pep-0643/

[di]

There's a couple levels of 'validation' that could happen for the Dynamic field here:

1. Validate that Name and Version are not marked as Dynamic (feasible)
2. Validate that wheels do not set Dynamic (probably feasible)
3. Validation across multiple artifacts (probably infeasible):
   • If a field is not marked as Dynamic, then the value of the field in any wheel built from the sdist MUST match the value in the sdist. If the field is not in the sdist, and not marked as Dynamic, then it MUST NOT be present in the wheel.
   • If a field is marked as Dynamic, it may contain any valid value in a wheel built from the sdist (including not being present at all).
   • Backends MUST NOT mark a field as Dynamic if they can determine that it was generated from data that will not change at build time.

Are we OK with only doing 1 & 2? (cc @pfmoore)

[konstin]

From my perspective just allowing 2.2 when no Dynamic is used would already be great and solve PyO3/maturin#564

[pfmoore]

I think (1) is reasonable. The PEP allows wheels to set Dynamic, so I think (2) is wrong, and should be omitted. I'm happy that Warehouse shouldn't try to do (3).

[di]

The PEP allows wheels to set Dynamic, so I think (2) is wrong, and should be omitted.

Got it. I was taking this from the original issue and thought I was missing something in the PEP. I'll update the OP accordingly.

If all we need to do is 1) then this is straightforward.

[domdfcoding]

What's the next step for this? Is it just waiting on a PR?

[di]

Yes.