Dear Maintainer,
In a simple distutils project:
$ cat hello
#!/usr/bin/env python3 print("Hello world")
$ cat setup.py
from distutils.core import setup
setup(name='hello', scripts=['hello'])
Installing it with --prefix is not fully honored, as "local" is always
added (--root is optional, used just to make the reproducer easier):
$ python3 setup.py install --root=/tmp/py-root --prefix=/opt/py-prefix
$ find /tmp/py-root/
/tmp/py-root/
/tmp/py-root/opt
/tmp/py-root/opt/py-prefix
/tmp/py-root/opt/py-prefix/local
/tmp/py-root/opt/py-prefix/local/bin
/tmp/py-root/opt/py-prefix/local/bin/hello
/tmp/py-root/opt/py-prefix/local/lib
/tmp/py-root/opt/py-prefix/local/lib/python3.12
/tmp/py-root/opt/py-prefix/local/lib/python3.12/dist-packages
/tmp/py-root/opt/py-prefix/local/lib/python3.12/dist-packages/hello-0.0.0-py3.12.egg-info
/tmp/py-root/opt/py-prefix/local/lib/python3.12/dist-packages/hello-0.0.0-py3.12.egg-info/dependency_links.txt
/tmp/py-root/opt/py-prefix/local/lib/python3.12/dist-packages/hello-0.0.0-py3.12.egg-info/SOURCES.txt
/tmp/py-root/opt/py-prefix/local/lib/python3.12/dist-packages/hello-0.0.0-py3.12.egg-info/top_level.txt
/tmp/py-root/opt/py-prefix/local/lib/python3.12/dist-packages/hello-0.0.0-py3.12.egg-info/PKG-INFO
In fact in such case everything should be installed in
/tmp/py-root/opt/py-prefix prefix and not
/tmp/py-root/opt/py-prefix/local since a prefix is explicitly defined
and so there's no point to add an extra "/local" subpath.
---
In between the others, this breaks jhbuild builds as a test fails for
this specific reason (see bug #1054720 where the missing file is due to
the fact that it gets installed to $PREFIX/local/bin instead of $PREFIX/bin).
---
After some debugging of it, this related to the default scheme change
happened with python3.10 [1] which meant to always use /usr/local as
default and ensure that one should explicitly require for /usr prefix,
but in the case that --prefix= is used, the user request is now ignored because:
- /usr/lib/python3.*/_distutils_system_mod.py:
1. Selects the scheme `posix_prefix` since we've requested a prefix explicitly
- /usr/lib/python3/dist-packages/setuptools/_distutils/command/install.py
1. Calls sysconfig.get_preferred_scheme("prefix") that now as per the said
change would return by default `posix_local` unless we're building a
debian package.
2. Replaces the variables to use the `posix_local` scheme
So, in order to fix this we may in theory change python3 packages to
make 1. to select another defined prefix say `posix_explicitprefix`, and
then making `sysconfig.get_preferred_scheme("explicitprefix")` to
instead return `posix_prefix`, but that would not be correct, because
being that a public API it should only support the allowed input
arguments for it ("prefix", "home" or "user").
As per this, I feel the best way to handle this is instead in the
setuptools module so that we can check once again if --prefix has been
used and react accordingly.
[1] https://lists.debian.org/debian-python/2022/03/msg00039.html
[2] https://bugs.launchpad.net/ubuntu/+source/python3.10/+bug/1967920