Warnings for skipped <pkg>.dist-info are unclear when METADATA file is missing

[zanieb]

Description

When you uninstall a package with extra files (as described in #12445) you can end up in a bad state where pip warns due to the existence of an invalid dist-info directory e.g.

WARNING: Skipping .venv/lib/python3.11/site-packages/idna-3.6.dist-info due to invalid metadata entry 'name'

However, this warning is shown in cases where there is no METADATA file at all and it's not clear how to resolve this as a user.

Expected behavior

Instead of suggesting that the metadata has an invalid 'name', the warning should suggest that the dist-info is invalid

WARNING: Skipping .venv/lib/python3.11/site-packages/idna-3.6.dist-info due to invalid due to missing METADATA file

Perhaps there's even a better user experience to be had here? Curious to hear others' thoughts.

pip version

23.3.2

Python version

3.11.4

OS

macOS

How to Reproduce

Here, we construct a bad dist-info entry manually though a user can get in this state accidentally without editing site-packages.

python -m venv .venv
source .venv/bin/activate
python -m pip install pip==23.3.2 > /dev/null 2>&1

set -eux

SITE_PACKAGES=$(python -c 'import site; print(site.getsitepackages()[0])')

# Create a bad dist-info entry
mkdir -p $SITE_PACKAGES/foo.dist-info
touch $SITE_PACKAGES/foo.dist-info/FOO

# Warning is not clear during `pip` command
pip list

rm -rf .venv

Output

++ python -c 'import site; print(site.getsitepackages()[0])'
+ SITE_PACKAGES=.venv/lib/python3.11/site-packages
+ mkdir -p .venv/lib/python3.11/site-packages/foo.dist-info
+ touch .venv/lib/python3.11/site-packages/foo.dist-info/FOO

+ pip list
WARNING: Skipping .venv/lib/python3.11/site-packages/foo.dist-info due to invalid metadata entry 'name'
Package    Version
---------- -------
pip        23.3.2
setuptools 65.5.0

+ rm -rf .venv

Code of Conduct

• I agree to follow the PSF Code of Conduct.

[TishyaaChaudhry]

I would like to work on this if it is still open

[sanspareilsmyn]

Is it fixed? If it's not, I would love to contribute on it:)

[uranusjr]

No PR linked so I assume this is open. Feel free.

[eevelweezel]

I have been doing testing as part of pull request #13402. The reproducer in the ticket contains an invalid .dist-info directory name (missing the version), and I can't reproduce the problem using a properly formatted .dist-info name, even if the METADATA file is missing. Unless someone can provide an example of why we should expect to encounter invalid .dist-info directories, I am inclined to close my PR, as I think the error message as it exists is valid.