Errors with v49.2.0's distutils adoption

[hugovk]

Related to #2256 / #2259.

When upgrading to setuptools>=49.1.3 for the #2249 fix for Pillow, we get the new warning in v49.2.0:

/home/travis/virtualenv/python3.9-dev/lib/python3.9/site-packages/setuptools/distutils_patch.py:25: UserWarning: Distutils was imported before Setuptools. This usage is discouraged and may exhibit undesirable behaviors or errors. Please use Setuptools' objects directly or at least import Setuptools first.

This also causes some C build issues and this sanity test failure; Pillow checks the version in the lower-level C code ("Core version") matches that in the user-facing Python code ("Pillow version"):

/home/travis/virtualenv/python3.9-dev/lib/python3.9/site-packages/Pillow-7.3.0.dev0-py3.9-linux-x86_64.egg/PIL/Image.py:115: RuntimeWarning: The _imaging extension was built for another version of Pillow or PIL:
Core version: None
Pillow version: 7.3.0.dev0

---

Moving the setuptools import before distutils in our setup.py removes the warning but not the error.

https://travis-ci.org/github/hugovk/Pillow/builds/707730154

I've not dug into this further, but it's happening at least on all the Linux/Python versions tested on Travis (3.5-3.9), and wanted to let you know.

More details at python-pillow/Pillow#4784 (comment).

[mattip]

also see numpy/numpy#16851 where we are trying to work around this. The problem is there is no way of knowing where exactly distutils is being imported.

[pganssle]

@mattip I think it would be prudent to hold off on trying to fix the warnings at the moment. I think #2259 / #2260 will likely be resolved before the distutils adoption is re-enabled by default.

(Though replacing distutils with setuptools wherever possible is worthwhile irrespective of the distutils injection strategy.)

[mattip]

Though replacing distutils with setuptools wherever possible is worthwhile

Numpy has distutils extensions, and I hope nothing will break on esoteric combinations like f2py + (mingw or intel compilers)

[pganssle]

Numpy has distutils extensions, and I hope nothing will break on esoteric combinations like f2py + (mingw or intel compilers)

I don't really understand what that "distutils extensions" means. setuptools will be the canonical implementation of "distutils" in the future. Some of the distutils hierarchy already is duplicated in setuptools (like commands), the parts that are likely to remain supported will likely move into the setuptools (I suspect that will include things like exceptions) namespace, and some stuff that is no longer necessary will be deprecated and removed.

If you need something from the distutils namespace and it's not available in setuptools, continue to use it until we provide an alternative (I would say "raise an issue" but I am not sure if we're going to just do a bulk migration or not), but if there's already an equivalent in setuptools, switching over to using setuptools now is the best thing you can do (and you should report any issues you encounter when doing this).

[pllim]

Hello. I tried to replace distutils with setuptools but not sure how to replace these:

from distutils.version import LooseVersion
from distutils import log

Thanks for your help!

[hugovk]

One option to replace distutils.version is packaging.version.parse:

• https://stackoverflow.com/a/11887885/724176
• Replace distutils.version with packaging.version.parse python-pillow/Pillow#4797