Declarative config breaks installs for old setuptools

[brandon-leapyear]

Reproduction:

python3 -m venv venv
venv/bin/pip install flake8-mutable

The flake8-mutable project uses pytest-runner in setup_requires (ref), which installs packages via easy_install and not through pip (https://pip.readthedocs.io/en/1.4.1/cookbook.html#controlling-setup-requires), which is probably the reason why our CI is currently crashing:

Collecting flake8-mutable==1.2.0 (from -c python/requirements/constraints.txt (line 43))
  Downloading https://nexus.build-leapyear.com/repository/pypi/packages/97/6a/0fd1d903848fe043c7b6e5283d9def56425754098e69d7683a3ccbbea345/flake8-mutable-1.2.0.tar.gz
    Complete output from command python setup.py egg_info:
    /root/.lybuild/miniconda-4.3.31/lib/python3.6/distutils/dist.py:261: UserWarning: Unknown distribution option: 'use_scm_version'
      warnings.warn(msg)
    warning: install_lib: 'build/lib' does not exist -- no Python modules to install
    
    zip_safe flag not set; analyzing archive contents...
    
    Installed /tmp/pip-install-hsfxj0l7/flake8-mutable/.eggs/UNKNOWN-0.0.0-py3.6.egg
    Traceback (most recent call last):
      File "<string>", line 1, in <module>
      File "/tmp/pip-install-hsfxj0l7/flake8-mutable/setup.py", line 40, in <module>
        'Programming Language :: Python :: 3.6',
      File "/root/.lybuild/miniconda-4.3.31/lib/python3.6/distutils/core.py", line 108, in setup
        _setup_distribution = dist = klass(attrs)
      File "/root/src/venv/lib/python3.6/site-packages/setuptools/dist.py", line 315, in __init__
        self.fetch_build_eggs(attrs['setup_requires'])
      File "/root/src/venv/lib/python3.6/site-packages/setuptools/dist.py", line 361, in fetch_build_eggs
        replace_conflicting=True,
      File "/root/src/venv/lib/python3.6/site-packages/pkg_resources/__init__.py", line 853, in resolve
        raise DistributionNotFound(req, requirers)
    pkg_resources.DistributionNotFound: The 'pytest-runner' distribution was not found and is required by the application
    
    ----------------------------------------
Command "python setup.py egg_info" failed with error code 1 in /tmp/pip-install-hsfxj0l7/flake8-mutable/

[jaraco]

That's weird to me that pytest-runner installed as "UNKNOWN-0.0.0"... even with easy_install... because not much changed except the shift from imperative to declarative config.

Oh! That could be it... if you have a version of setuptools that doesn't support declarative config (30.4 or later I believe), the package name would not be present. I suspect that's the issue. Can you confirm you have an older version of setuptools?

[jaraco]

Given that this is flagged as urgent, and given that the 4.3 release wasn't at all an important release, I'd like to pull it from PyPI. I worry if I pull it from PyPI, I won't have a good path to test to avoid this issue. Perhaps I could re-release it as 5.0 some time after packages that rely on it have had a chance to pin against it.

Thoughts?

[brandon-leapyear]

Yes, I have setuptools 28.8.0. I'm using Python 3.6.3 from Anaconda. Unsure how to upgrade setuptools.

I agree, this is breaking a lot of things, and we are currently going through a release cycle, so we desperately need our CI working. I think you should pull it from PyPI, search for all packages using pytest-runner in setup_requires, make sure they all pin pytest-runner in setup_requires, and re-release with a major release at some point

[brandon-leapyear]

Alternatively, I just checked that pip install -U setuptools works. This is not URGENT for us anymore, but I would still recommend pulling from PyPI until you give advanced notice to other packages that pytest-runner will soon require setuptools >= 30.4

[jaraco]

I’ve pulled the 4.3 release .

[jaraco]

I've re-released pytest-runner 4.2 as 4.3.1 to ensure it supersedes the 4.3 release. I've furthermore added a change note in that release that 5.x (or later) will drop support. I do worry that even when releasing a 5.x release, projects are unlikely to have seen the advance notice.

[jaraco]

Now that I think about it, pytest-runner can probably warn if it's launched under a setuptools that can't support declarative config.