Make assertion rewrite warning messages filterable

[ikappaki]

Hi,

can you please consider patch to mare assertion rewrite warning messages filterable using the standard -W option. It addresses #5473.

The issue arises when a Python package defines a pytest plugin, and also calls pytest.main() programmatically, after importing one of its own submodules. Because the module is already imported, pytest.main() cannot rewrite its assertions and emits a warning like:

Module already imported so cannot be rewritten: basilisp

Unfortunately, the : in the message conflicts with Python’s warning filter syntax, where : is used as a delimiter. This prevents users from filtering out the warning via -W.

This patch replaces the : in the warning message with a ;, making it possible to write a valid warning filter like:

-W ignore:Module already imported so cannot be rewritten; mymodule:pytest.PytestAssertRewriteWarning

We believe there's no need to force assertion rewriting simply because a module defines a plugin, and users should be able to suppress this warning when needed.

For background and alternative solutions considered, see #5473 (comment).

Happy to discuss further or consider alternatives.

• Include new tests or update existing tests when applicable.
• Allow maintainers to push and squash when merging my commits. Please uncheck this if you prefer to squash the commits yourself.
• Create a new changelog file in the changelog folder

Thanks

[nicoddemus]

Looks great, simple and to the point! Thanks @ikappaki!

[RonnyPfannschmidt]

Arent other regex matches avaliable to match?

[ikappaki]

HI @RonnyPfannschmidt,

The issue is that the string passed to the -W command line option is treated as a literal, so regex characters have no effect:
https://docs.pytest.org/en/stable/how-to/capture-warnings.html#controlling-warnings:

i.e., in CPython, the message portion is escaped using re.escape:
https://github.com/python/cpython/blob/e1f891414b2329414a6160ed246f5f869a218bfd/Lib/_py_warnings.py#L359-L384

[RonnyPfannschmidt]

So we should aim for warning filters in pytest settings instead of using slightly off characters in the long run

[nicoddemus]

So we should aim for warning filters in pytest settings instead of using slightly off characters in the long run

You OK to merge the PR or would you like to hold it off to discuss it further?

[RonnyPfannschmidt]

Let's merge it for now

But eventually id like to be able to block the warnings properly