gh-85567: Register a cleanup function to close files for FileType objects in argparse

[achhina]

BPO-41395

• Signed CLA
• Ran tests and make patchcheck
• Added News Entry

Hello! First-time contribution, I've read through what I believe to be the relevant sections in the Python Developer's Guide, however, feel free to let me know if there is something I missed.

This is a follow-up to PR-21702, where it was suggested to address the ResourceWarning issue directly in argparse itself. However, as that was discussed back in 2020, I've attempted to take a stab at it myself! After reading a suggestion from @facundobatista, I have added a file.close cleanup function with atexit for files opened with FileType objects, to ensure they are always closed.

Previously:

❯ ./python.exe -Wall -m pickle p1              
{'a': 1}
sys:1: ResourceWarning: unclosed file <_io.BufferedReader name='p1'>

❯ ./python.exe -Wall -m pickle p1 p2
/user: ResourceWarning: unclosed file <_io.BufferedReader name='p1'>
  value = [self._get_value(action, v) for v in arg_strings]
ResourceWarning: Enable tracemalloc to get the object allocation traceback
usage: pickle.py [-h] [-t] [-v] [pickle_file ...]
pickle.py: error: argument pickle_file: can't open 'p2': [Errno 2] No such file or directory: 'p2'

With Patch:

❯ ./python.exe -Wall -m pickle p1   
{'a': 1}

❯ ./python.exe -Wall -m pickle p1 p2
usage: pickle.py [-h] [-t] [-v] [pickle_file ...]
pickle.py: error: argument pickle_file: can't open 'p2': [Errno 2] No such file or directory: 'p2'

https://bugs.python.org/issue41395

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[achhina]

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I had signed the CLA last night, so just waiting for it to be processed.

[achhina]

Hi @facundobatista @serhiy-storchaka,

As both of you had reviewed PR-21702 and this follows up on that, would you be available to review this?

[facundobatista]

Hello! Thanks for the work! I annotated a couple of small suggestions.

[bedevere-bot]

A Python core developer has requested some changes be made to your pull request before we can consider merging it. If you could please address their requests along with any other requests in other reviews from core developers that would be appreciated.

Once you have made the requested changes, please leave a comment on this pull request containing the phrase I have made the requested changes; please review again. I will then notify any core developers who have left a review that you're ready for them to take another look at this pull request.

[ghost]

All commit authors signed the Contributor License Agreement.

[achhina]

Thanks for taking a look @facundobatista!

I have made the requested changes; please review again

[bedevere-bot]

Thanks for making the requested changes!

@facundobatista: please review the changes made to this pull request.

[facundobatista]

It looks great! Thanks!