Description

peterzahemszky

opened on May 26, 2022

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The version() function of the importlib.metadata package returns an arbitrary version number when called with None. There's no documentation on what the return value means.

I would have expected one of the following instead:

• raise an error saying that the distribution_name parameter cannot be None, or
• explain what the return value means in the relevant documentation.

The current behaviour is confusing as one could think, for example, that the return value is the version of the project/package they call it from.

>>> import sys
>>> print(sys.version)
3.10.0 (tags/v3.10.0:b494f59, Oct  4 2021, 19:00:18) [MSC v.1929 64 bit (AMD64)]
>>> import importlib.metadata
>>> importlib.metadata.version(None)
'21.2.3'

I looks like the return value is the version of an arbitrary package installed in the Python virtual environment. Calling the function repeatedly seems to give the same value, but installing a new package can cause the return value to change.

System information

• CPython versions tested on: 3.10.0
• Operating system and architecture: Windows 10 Enterprise (64-bit operating system, x64-based processor)

Activity

1. peterzahemszky

   added

   type-bugAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error

   on May 26, 2022
2. warsaw commented on May 26, 2022

   

   warsaw

   on May 26, 2022

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   I can't think of a valid meaning for distribution_name=None in this or any related API. In a fresh checkout of CPython main, you do get an exception, but probably not the right one. It should probably quick raise a ValueError.

   @jaraco

   Python 3.12.0a0 (heads/main:da39719483, May 26 2022, 09:01:35) [Clang 13.1.6 (clang-1316.0.21.2.5)] on darwin
   Type "help", "copyright", "credits" or "license" for more information.
   >>> from importlib.metadata import version
   >>> version(None)
   Traceback (most recent call last):
     File "<stdin>", line 1, in <module>
     File "/Users/barry/projects/python/cpython/Lib/importlib/metadata/__init__.py", line 991, in version
       return distribution(distribution_name).version
              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
     File "/Users/barry/projects/python/cpython/Lib/importlib/metadata/__init__.py", line 964, in distribution
       return Distribution.from_name(distribution_name)
              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
     File "/Users/barry/projects/python/cpython/Lib/importlib/metadata/__init__.py", line 561, in from_name
       raise PackageNotFoundError(name)
       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   importlib.metadata.PackageNotFoundError: No package metadata was found for None
   
3. jaraco commented on Jun 23, 2022

   

   jaraco

   on Jun 23, 2022

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   I'm unsure whether the input should produce a ValueError or a TypeError, but it also occurs to me that an empty string may also produce unexpected results.

   $ pip-run -q importlib_metadata -- -c "import importlib_metadata as md; print(md.version(''))"
   4.11.4
   $ py -3.11 -c "import importlib.metadata as md; print(md.version(''))"
   16.4.0
   
4. jaraco commented on Jun 23, 2022

   

   jaraco

   on Jun 23, 2022

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   Hmm. The way it's currently implemented, distribution_name is passed through as Context.name where None is defined to mean "all distributions", and Distribution._from_name is implemented to return the first matching distribution. I expect the only reason that Barry is getting the PackageNotFoundError is because he's running in an environment where there are literally no distributions, but if there were a single distribution installed, I'd expect him to get the version for that one.
5. jaraco commented on Jun 23, 2022

   

   jaraco

   on Jun 23, 2022

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   I have a test capturing the failure and a potential fix in the aforementioned PR.
6. jaraco

   added 2 commits that reference this issue on Jun 25, 2022

   In Distribution.from_name, require a non-empty string. Fixes python/c…

   This issue will close once commit f9c082a is merged into the 'main' branch.

   f9c082a

   In Distribution.from_name, require a non-empty string. Fixes python/c…

   This issue will close once commit eb19c64 is merged into the 'main' branch.

   eb19c64
7. jaraco

   closed this as completedin importlib_metadata#391on Jun 25, 2022
8. warsaw commented on Jun 25, 2022

   

   warsaw

   on Jun 25, 2022

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   I expect the only reason that Barry is getting the PackageNotFoundError is because he's running in an environment where there are literally no distributions, but if there were a single distribution installed, I'd expect him to get the version for that one.

   Indeed, and all I need to do to see the difference is invoke Python from a ./python.exe -m venv. Then I get 22.0.4 (from Python 3.12), which is of course the version of the pip distribution in the venv.
9. jaraco

   added a commit that references this issue on Jun 26, 2022

   gh-93259: Validate arg to ``Distribution.from_name``. (GH-94270)

   38612a0
10. serhiy-storchaka

    added a commit that references this issue on Jun 26, 2022

    Revert 30935 defer bpo45162 to 312 (#94285)

    1ffde3e
11. clrpackages

    added a commit that references this issue on Jun 28, 2022

    pypi-importlib_metadata: Autospec creation for update from version 4.…

    This issue will close once commit bb5ba57 is merged into the 'main' branch.

    bb5ba57

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