gh-101696: Make sure immutable types have a valid version tag by erlend-aasland · Pull Request #101742 · python/cpython

tl;dr I'm on board with this.

As I mentioned in gh-101696, this is good as it covers non-builtin static types (AKA non-_Py_TPFLAGS_STATIC_BUILTIN), e.g. in community extension modules. ¹ (The switch to Py_TPFLAGS_IMMUTABLETYPE seems fine.)

FWIW, the already merged fix may fit a little better with the vague idea (in my head) that we should be special-casing static types in the runtime as little as possible (or otherwise in more explicit ways, like the dedicated _PyStaticType_Dealloc()). In that spirit, rather than modifying PyType_Ready(), I was going to suggest we could find a way to apply _PyStaticType_Dealloc() to all static types, not just the builtin ones, which might be a good idea regardless. However, that feels like overkill for fixing this issue. Plus, we're already special-casing static types here in PyType_Ready(). (Perhaps my mental model is misaligned...)

Bottom line: dropping the original fix and adding the fix you have here is worth it since it handles non-builtin static types too.

Footnotes

1. One could argue that non-builtin (non-core) static types should be discouraged (basically, they already are) and we shouldn't bother adding extra maintenance burden--however small--to accommodate them. However, that's not where the community is at nor will be for a long time and there's no reason to be so hard-line about it, especially in a case like this where the additional maintenance burden is essentially zero. ↩