PytestConfigWarning about unknown keys can't be suppressed

[The-Compiler]

@The-Compiler With pytest.PytestConfigWarning the INTERNALERROR is gone but I still get the warnings. I have even tried to ignore all PytestConfigWarning but with no success.

filterwarnings =
    ignore::pytest.PytestConfigWarning

This means, filterwarnings does nothing in my case. How can I suppress these warnings?

============================== warnings summary ===============================
venv\lib\site-packages\_pytest\config\__init__.py:1148
  venv\lib\site-packages\_pytest\config\__init__.py:1148: PytestConfigWarning: Unknown config ini key: flake8-ignore
  
    self._warn_or_fail_if_strict("Unknown config ini key: {}\n".format(key))

venv\lib\site-packages\_pytest\config\__init__.py:1148
  venv\lib\site-packages\_pytest\config\__init__.py:1148: PytestConfigWarning: Unknown config ini key: flake8-max-line-length

_Originally posted by @marincandenza in https://github.com/pytest-dev/pytest/issues/7612#issuecomment-668993473_

[The-Compiler]

I can reproduce with:

[pytest]
doesnotexist = 42
filterwarnings = ignore::pytest.PytestConfigWarning

I'm guessing the warning gets emitted before pytest's warning filtering is initialized, which is a bit unfortunate...

[nicoddemus]

Yeah a bit, what happens is:

We want to issue warnings during the configure stage. Unfortunately at that stage, it might happen that the warnings plugin has not even been configured yet, so warnings issued using warnings.warn would not be captured at all.

The workaround devised at the time was to call _issue_warning_captured, which calls warnings.warn but also manually triggers pytest_warning_recorded. That's the reason why we can still show it in the terminal.

Perhaps a way to fix the general case is to special case warnings, by installing the filters early as possible, even before the warnings plugin is initialized. This would require some refactoring though.

[nicoddemus]

Actually for this specific warning it seems possible, see #7649.