importlib.resources.as_file is leaving temporary file pointers open

[samety]

Bug report

importlib.resources.as_file is leaving temporary file pointers open after writing their contents
see _write_contents function in importlib/resources/_common.py

Easy to repeat, just run the test case below with -We
Lib.test.test_importlib.resources.test_resource.ResourceFromZipsTest01.test_as_file_directory

Your environment

• CPython versions tested on: Python 3.12.0a3+
• Operating system and architecture: Ubuntu 22.04.1 LTS

I think it just needs to use Path.write_bytes and keep the file pointer closed.

Linked PRs

• gh-100585: Fixed a bug where importlib.resources.as_file was leaving file pointers open #100586

[warsaw]

Just from a quick glance, I think you're right in that the code is relying on implicit GC to close the file, which generally isn't good practice. @jaraco to chime in. What I don't remember is whether its resources or metadata that @jaraco likes to fix upstream and then sync to CPython. (I haven't looked to see if the same code exists in importlib_resources.)

[jaraco]

This issue is fixed in python/importlib_resources#274, which just hasn't been merged into CPython yet. All skeleton-based projects (including importlib_metadata) now enable ResourceWarnings so these kinds of issues will get caught early.

In that fix, a context manager was used instead of relying on write_bytes. I do prefer this one-line approach with write_bytes.

[samety]

Yes I just saw the context manager fix, that's also addressing the issue indeed. I also like one line approach more, I find using write_bytes a bit cleaner. I don't mind applying the same one line approach to the importlib_resources project if that's the preferred option. Please let me know if you prefer a PR to importlib_resources instead of this one.

[jaraco]

I cherry-picked the change into importlib_resources as python/importlib_resources@d623078. Thanks for reporting and the fix.