packages_distributions doesn’t work for some dist-info packages built outside Setuptools

[flying-sheep]

I assume that for those packages, something similar to the following will work to retrieve the top level packages/modules contained in a distribution

{
    f.parts[0] if len(f.parts) > 1 else f.with_suffix('').name
    for f in pkg.files if f.suffix == ".py"
}

Of course there’s a lot of edgecases

[FFY00]

Yeah, because we are looking for top_level.txt, which AFAIK is a setuptools-specific thing. As you point out, the logic you suggest is fragile, so we need a better mechanism. top_level.txt is not defined in any PEP I could find, it's only defined in eggs. I think we may want to propose this to be added as an optional part of the project metadata.

[FFY00]

FYI, the original discussion is in #131.

[jaraco]

It works for me:

~ $ pip-run importlib_metadata requests -- -c "import importlib_metadata as md; print(md.packages_distributions()['requests'])"
Collecting importlib_metadata
  Using cached importlib_metadata-4.6.4-py3-none-any.whl (17 kB)
Collecting requests
  Using cached requests-2.26.0-py2.py3-none-any.whl (62 kB)
Collecting zipp>=0.5
  Using cached zipp-3.5.0-py3-none-any.whl (5.7 kB)
Collecting charset-normalizer~=2.0.0
  Using cached charset_normalizer-2.0.4-py3-none-any.whl (36 kB)
Collecting idna<4,>=2.5
  Using cached idna-3.2-py3-none-any.whl (59 kB)
Collecting certifi>=2017.4.17
  Using cached certifi-2021.5.30-py2.py3-none-any.whl (145 kB)
Collecting urllib3<1.27,>=1.21.1
  Using cached urllib3-1.26.6-py2.py3-none-any.whl (138 kB)
Installing collected packages: zipp, urllib3, idna, charset-normalizer, certifi, requests, importlib-metadata
Successfully installed certifi-2021.5.30 charset-normalizer-2.0.4 idna-3.2 importlib-metadata-4.6.4 requests-2.26.0 urllib3-1.26.6 zipp-3.5.0
['requests']

The title says "some dist-info packages". Can you provide maybe one example that doesn't work?

[FFY00]

Non-setuptools ones, see my comment above.

$ pip-run importlib_metadata hidabc -- -c "import importlib_metadata as md; print(md.packages_distributions()['hidabc'])"
Traceback (most recent call last):
  File "<string>", line 1, in <module>
KeyError: 'hidabc'

[jaraco]

In #340, I've drafted a change that implements the proposed approach above as a fallback when top-level isn't available.