pure-Python warn_explicit() passes wrong arg to WarningMessage

[jwilk]

The pure-Python implementation of the warnings.warn_explicit() function does this:

msg = WarningMessage(message, category, filename, lineno, source)

But the 5th argument of WarningMessage is file (the file the message is supposed to be printed into), not source ("the destroyed object which emitted a ResourceWarning").

Here's how to reproduce the bug:

>>> import sys, importlib, warnings
>>> warnings.warn_explicit('eggs', UserWarning, 'eggs.py', 42, source=object())
eggs.py:42: UserWarning: eggs
Object allocated at (most recent call last):
  File "<stdin>", lineno 1
>>> # so far so good; now let's try the same with pure-Python implementation
>>> sys.modules['_warnings'] = None
>>> importlib.reload(warnings)
<module 'warnings' from '/usr/lib/python3.12/warnings.py'>
>>> warnings.warn_explicit('eggs', UserWarning, 'eggs.py', 42, source=object())
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python3.12/warnings.py", line 413, in warn_explicit
    _showwarnmsg(msg)
  File "/usr/lib/python3.12/warnings.py", line 115, in _showwarnmsg
    _showwarnmsg_impl(msg)
  File "/usr/lib/python3.12/warnings.py", line 30, in _showwarnmsg_impl
    file.write(text)
    ^^^^^^^^^^
AttributeError: 'object' object has no attribute 'write'

Linked PRs

• gh-129843: Fix the wrong argument passed - converting positional argument to named argument #129848
• [3.13] gh-129843: fix pure Python implementation of warnings.warn_explicit (GH-129848) #131349
• [3.12] gh-129843: fix pure Python implementation of warnings.warn_explicit (GH-129848) #131350

[picnixz]

This indeed looks wrong. Do you want to send a PR fixing this? The patch is rather easy as you just need to write WarningMessage(message, category, filename, lineno, source=source) I think.

[jwilk]

Do you want to send a PR fixing this?

No.

[sergey-miryanov]

I can take this if no one else wants it.

[picnixz]

Go ahead Sergey!

[picnixz]

@srinivasreddy In the future, it would be nice not to make a PR when someone else has already suggested to do it. If they do not open one for a few days, it's also better to first ask them if they are still working on the task.

[srinivasreddy]

Apologies for raising the PR. If @sergey-miryanov wanted to raise PR, I am fine to close mine .

[sergey-miryanov]

@srinivasreddy
You already did. I'm okay with that.