Comment by zahlman
21 hours ago
> If setup.py was working okay for folks, what incentivized them to start using pyproject.toml?
It wasn't working okay for many people, and many others haven't started using pyproject.toml.
For what I consider the most egregious example: Requests is one of the most popular libraries, under the PSF's official umbrella, which uses only Python code and thus doesn't even need to be "built" in a meaningful sense. It has a pyproject.toml file as of the last release. But that file isn't specifying the build setup following PEP 517/518/621 standards. That's supposed to appear in the next minor release, but they've only done patch releases this year and the relevant code is not at the head of the repo, even though it already caused problems for them this year. It's been more than a year and a half since the last minor release.
That's really unfortunate, and it sounds like a quick thing to fix. Is there a pull request with that?
I should have mentioned one of the main reasons setup.py turns out not okay for people (aside from the general unpleasantness of running code to determine what should be, and mostly is, static metadata): in the legacy approach, Setuptools has to get `import`ed from the `setup.py` code before it can run, but running that code is the way to find out the dependencies. Including build-time dependencies. Specifically Setuptools itself. Good luck if the user's installed version is incompatible with what you've written.