24.3 release uses unreleased vendored `packaging`, breaking devendored systems

[mgorny]

Description

The 24.3 release of pip started using ios_platforms which are not a part of any release. This is in violation of the vendoring policy, and makes it impossible to run new pip with dependencies devendored.

Expected behavior

pip using a released version of packaging.

pip version

24.3

Python version

n/a

OS

Gentoo Linux amd64

How to Reproduce

1. Devendor dependencies according to pip/_vendor/vendor.txt.
2. Try to run pip.

Output

No response

Code of Conduct

• I agree to follow the PSF Code of Conduct.

[ichard26]

Hi, sorry about the breakage here. This wasn't intentional, although was definitely an oversight on our part.

The path forward here would be either:

• Revert the PR and wait until the local patches are upstreamed in a published release of packaging
• Modify pip's source to gracefully handle a non-patched packaging (i.e. if this import fails, silently drop iOS support)

I'd prefer reverting the PR for simplicity and to bring pip closer into with the vendoring policy. OTOH, at a glance, option 2 would only involve a small tweak. And I guess it could be more disruptive to rip out a nontrivial change in a bugfix release. Thoughts @sbidoul?

Finally, I do think we need to follow our vendoring policy more strictly, while it is possible to use unreleased versions of libraries without breaking downstream, this seems likely to be a minefield (where we'd inevitably screw up). Otherwise, the policy needs to be reworded to permit non-essential patches that only fail gracefully when the patched libraries are replaced.

[freakboy3742]

Author of the original patch here.

I'd argue there's another possible fix here - work with/encourage packaging to publish a new release. It's been 5 months since packaging has made a release, so one would seem due (given the historical release cadence).

FWIW, reverting would also be disruptive to my own efforts to get PEP 730 support in the broader Python ecosystem; so I've provided #13057 as an import-based workaround for the problem.

[mgorny]

I don't think reverting is really necessary. I think a new release of packaging would be best, with graceful fallback being the second best.

[pradyunsg]

I should be able to cut a packaging release sometime in the coming days (it's past midnight where I am right now, but I should be able to cut one tomorrow depending on how jet lag treats me).