py313: mark Linux-only decimal allowlist entries as unfixable for now

[aminalaee]

Just to test with the pipeline

[AlexWaygood]

I think the parameter names changing only on Linux indicates that the setup-python build for Ubuntu is falling back to the pure-Python implementation of the decimal module instead of using the C implementation. This might be because the setup-python maintainers haven't (yet?) adjusted to the build changes CPython made in python/cpython#115119. In any event, I think this is probably something we shouldn't change in our stubs, as it's either a bug in CPython or setup-python, and it's not a change that people installing Python from python.org are likely to see.

[AlexWaygood]

I suggest that instead of trying to "fix" the Linux-only allowlist entries here, we move them to a separate section of the allowlist with a comment explaining why we shouldn't try to fix them at this point in time.

[aminalaee]

Yeah I think that makes sense, I initially started this PR to double-check what I'm seeing is right. I didn't want to start another discussion in the CPython repo (yet) 😅

[AlexWaygood]

It definitely seems like the setup-python Ubuntu build doesn't have the _decimal C extension installed for CPython 3.13.0b1. I'm not sure whether that's also going to be the case for 3.13.0b2 without changes at setup-python, or whether CPython has since made changes that mean that 3.13.0b2 will be okay.

@erlend-aasland, would you be able to clarify that at all? python/cpython#115119 is a long issue thread, and I'm not quite sure what the status is right now, as a non-expert in CPython's build system 😄 I don't want to open a bug report at setup-python if it will be fixed anyway when beta2 comes out!

[erlend-aasland]

3.13.0b2 build system will fall back to the CPython vendored (but deprecated) libmpdecimal library, so unlike 3.13.0b1, 3.13.0b2 should have the _decimal C extension.

See also:

• [3.13] gh-115119: Fall back to bundled libmpdec if system libmpdec is not found (GH-119196) cpython#119217

[AlexWaygood]

Thanks so much @erlend-aasland! @aminalaee, for the Linux-only stubtest allowlist entries, let's just do what I suggested in #12061 (comment) for now, in that case, since the allowlist entries will all go away naturally when we start using beta2 in CI :-)

[AlexWaygood]

Thanks!

[github-actions]

According to mypy_primer, this change has no effect on the checked open source code. 🤖🎉