Tootfinder

So #Gentoo #Python eclasses are pretty modern, in the sense that they tend to follow the best practices and standards, and eventually deal with deprecations. Nevertheless, they have a long history and carry quite some historical burden, particularly regarding to naming.
The key point is that the eclasses were conceived as a replacement for the old eclasses: "distutils" and "python". Hence, much like we revision ebuilds, I've named the matching eclasses "distutils-r1" and "python-r1". For consistency, I've also used the "-r1" suffix for the remaining eclasses introduced at the time: "python-any-r1", "python-single-r1" and "python-utils-r1" — even though there were never "r0"s.
It didn't take long to realize my first mistake. I've made the multi-impl eclass effectively the "main" eclass, probably largely inspired by the previous Gentoo recommendations. However, in the end I've found out that for the most use cases (i.e. where "distutils-r1" is not involved), there is no real need for multi-impl, and it makes things much harder. So if I were naming them today, I would have named it "python-multi", to indicate the specific use case — and either avoid designating a default at all, or made "python-single" the default.
What aged even worse is the "distutils-r1" eclass. Admittedly, back when it was conceived, distutils was still largely a thing — and there were people (like me) who avoided unnecessary dependency on setuptools. Of course, nowadays it has been entirely devoured by setuptools, and with #PEP517 even "setuptools" wouldn't be a good name anymore. Nowadays, people are getting confused why they are supposed to use "distutils-r1" for, say, Hatchling.
Admittedly, this is something I could have done differently — PEP517 support was a major migration, and involved an explicit switch. Instead of adding DISTUTILS_USE_PEP517 (what a self-contradictory name) variable, I could have forked the eclass. Why didn't I do that? Because there used to be a lot of code shared between the two paths. Of course, over time they diverged more, and eventually I've dropped the legacy support — but the opportunity to rename was lost.
In fact, as a semi-related fact, I've recognized another design problem with the eclass earlier — I should have gone for two eclasses rather than one: a "python-phase" eclass with generic sub-phase support, and a "distutils" (or later "python-pep517") implementing default sub-phases for the common backends. And again, this is precisely how I could have solved the code reuse problem when I introduced PEP517 support.
But then, I didn't anticipate how the eclasses would end up looking like in the end — and I can't really predict what new challenges the Python ecosystem is going to bring us. And I think it's too late to rename or split stuff — too much busywork on everyone.

Someone asked about fixing #setuptools deprecation warnings today (#Gentoo collects and reprints them, so people actually notice). I think my best hint is: use another build system.
#Python #PEP517

Some fun facts about #Python limited API / stable ABI.
1. #CPython supports "limited API". When you use it, you get extensions that are compatible with the specified CPython version and versions newer than that. To indicate this compatibility, such extensions use `.abi3.so` suffix (or equivalent) rather than the usual `.cpython-313-x86_64-linux-gnu.so` or alike.
2. The actual support is split between CPython itself and #PEP517 build systems. For example, if you use #setuptools and specify `py_limited_api=` argument to the extension, setuptools will pass appropriate C compiler flags and swap extension suffix. There's a similar support in #meson, and probably other build systems.
3. Except that CPython freethreading builds don't support stable ABI right now, so building with "limited API" triggers an explicit error from the headers. Setuptools have opted for building explicit about this: it emits an error if you try to use `py_limited_api` on a freethreading interpreter. Meson currently just gives the compile error. This implies that package authors need to actively special-case freethreading builds and enable "limited API" conditionally.
4. A some future versions of CPython will support "limited API" in freethreading builds. I haven't been following the discussions closely, but I suspect that it will only be possible when you target that version or newer. So I guess people will need to be building two stable ABI wheels for a time — one targeting older Python versions, and one targeting newer versions plus freethreading. On top of that, all these projects will need to update their "no 'limited API' on freethreading" conditions.
5. And then there's #PyPy. PyPy does not feature a stable ABI, but it allows you to build extensions using "limited API". So setuptools and meson just detect that there is no `.abi3.so` on PyPy, and use regular suffix for the extensions built with "limited API".

New reason not to use #PythonPoetry just dropped: they reinvented "reproducible builds", poorly. The problem is, they missed the purpose of reproducible builds entirely and they use it for source distributions too, and when you don't use SOURCE_DATE_EPOCH, they force all files to epoch (as in timestamp 0) instead of leaving them alone.
Like, all source distributions created by Poetry and uploaded to #PyPI now have 1970 timestamps that, simply speaking, break stuff. The most absurd thing is that ZIP can't handle that timestamp, so they override it and use another date for wheels 🤦.
#Gentoo #PEP517