Bug: filterwarnings doesn't work for pytest plugins

[jamesbraza]

In pytest-dev/pytest-asyncio@c74d1c3, pytest-asyncio==0.24.0 (which is a pytest plugin) added a PytestDeprecationWarning that I am now trying to silence.

I have noticed this PytestDeprecationWarning is different from normal dependencies' DeprecationWarning because it's emitted before pytest loads, instead of at test time.

I have configured filterwarnings for many normal packages, but I can't get it to work for this "pre-pytest loaded" PytestDeprecationWarning:

[tool.pytest.ini_options]
filterwarnings = [
    'ignore:configuration option "asyncio_default_fixture_loop_scope" is unset',
]

I have concluded that filterwarnings doesn't seem to work on pytest plugins.

Thus, I think this is a sort of bug, so I am requesting to apply filterwarnings also to pytest plugins, not just normal test time dependencies.

[dongfangtianyu]

Looks the same as #12697 .

Pytest will intercept and capture warnings in the collection of use cases.
Prior to this, if wanted to filter specified warnings, couldn't rely on pytest but on python.

for example

python -W ignore::DeprecationWarning    -m pytest

However, due to this line of code, doing so is actually ineffective:
https://github.com/pytest-dev/pytest/blob/main/src/_pytest/config/__init__.py#L1116

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It may be necessary a new feature :capture warnings when the plugin is loading.

[bluetech]

Thanks @dongfangtianyu for the reference, closing as a duplicate of #12697.