setup.py does not provide option --single-version-externally-managed

[ajaust]

As indicated in the Spack PR setup.py is lacking the option --single-version-externally-managed which makes it necessary to install the package in a non-standard way (from the Spack perspective). The lack of this option might indicate that setuptools is not used or differently than expected.

I did a quick check by removing the import of the setuptools modulessetup and test and it turns out that we need setuptools. Could it still be that distutils and setuptools interfere?

What behavior should be expected?

Link to PR: spack/spack#19558

[ajaust]

Update: The installation routine is actually based on distutils. If I change

    cmdclass={'test': my_test,
              'build_ext': my_build_ext,
              'build': my_build,
              'install': my_install},

to

    cmdclass={'test': my_test,
              'build_ext': my_build_ext,
              'build': my_build},

I get the compile option --single-version-externally-managed. Are we defining a useful installation routing? Should/Could it be derived from setuptools only without the use of distutils?

[ajaust]

Another update

Could this be the right imports for dropping distutils?

from enum import Enum
from setuptools import setup                                                                                                                                                                                                                                                          
from setuptools.command.test import test
from setuptools.command.install import install
from setuptools.command.build_py import build_py as build
from Cython.Distutils.extension import Extension
from Cython.Distutils.build_ext import new_build_ext as build_ext
from Cython.Build import cythonize

I am not sure about the redaclaration of build_py as build though.

[BenjaminRodenberg]

@ajaust thanks for opening this issue and already starting to investigate it!

Removing install as suggested in #64 (comment) sounds reasonable. I actually think we can also get rid of the other custom routines (except my_test), if we use the try: ... except ... variant in get_extensions instead of if ... else ... to find out whether we have to build the extension for testing or the real one.

I will try this out in a moment and open a PR.

The setup.py file has some history and therefore contains some really ugly code... good that this issue gives us a chance to clean this up.