pdm install started failing on Python 3.7 after importlib-metadata released v5.0.0

[FeodorFitsner]

A few hours ago importlib-metadata released v5.0.0 and pdm install started failing on Python 3.7.

Failing CI build: https://ci.appveyor.com/project/flet-dev/flet/builds/44943064/job/6j92ckkaol60n8q0#L98
Last good build: https://ci.appveyor.com/project/flet-dev/flet/builds/44942650/job/uxk5x5m152jrcl3r#L98

Steps to reproduce

pdm install

Actual behavior

Traceback (most recent call last):
  File "/home/appveyor/venv3.7.13/bin/pdm", line 8, in <module>
    sys.exit(main())
  File "/home/appveyor/venv3.7.13/lib/python3.7/site-packages/pdm/core.py", line 254, in main
    return Core().main(args)
  File "/home/appveyor/venv3.7.13/lib/python3.7/site-packages/pdm/core.py", line 55, in __init__
    self.load_plugins()
  File "/home/appveyor/venv3.7.13/lib/python3.7/site-packages/pdm/core.py", line 240, in load_plugins
    entry_points.get("pdm", []), entry_points.get("pdm.plugin", [])
AttributeError: 'EntryPoints' object has no attribute 'get'

Expected behavior

The command works normally.

[analogrithems]

i've just started seeing the same in my circle builds started yesterday

[menzenski]

We are seeing this as well (GitHub actions with setup-pdm action)

[lecardozo]

@frostming do you think updating the plugin loading snippet to the new importlib-metadata==5.0.0 EntryPoints would be enough? It seems to me that this API has diverged between importlib.metadata and importlib_metadata. 🤔

I've tried a quick fix to support this new API on this branch, but I'm not quite sure this will be enough to keep support for both 3.7 and >=3.8

[lecardozo]

I'm seeing a few options here:

• setting an upper bound for importlib-metadata (<5.0.0) for Python 3.7 (seems reasonable) (branch)
• keeping the code as is and dropping support for Python 3.7 (doesn't seem the best option, IMO)
• treating EntryPoints differently between different importlib-metadata major versions

Are there any other options that we should be considering?

[pawamoy]

I'd vote for the first solution: setting an upper bound for importlib-metadata (<5.0.0) for Python 3.7.
It's the most straight-forward fix, will not require more maintenance, and can easily be removed once Python 3.7 is EOL (which happens in middle of 2023 I think, so not far away). Users will just have to upgrade PDM, and done 🙂

[henryiii]

Option a) is just delaying the issue. Dict based access has been deprecated since importlib_metadata 3.6 and Python 3.10. Per Python's deprecation policy, this will be removed in Python 3.12. python/importlib_metadata#409 (comment).

The correct solution is to require importlib_metadata >= 3.6; python_version<"3.10", update the sys.version_info checks to < (3, 10), and use .select(...) instead.

[henryiii]

Ahh, pdm install bumps importlib_metadata up to 5, then nothing works anymore. So the current solution doesn't work even as a temporary one if a package you are using requires importlib_metadata>=5, which packages are starting to do. :(

[frostming]

Fixing in #1467