pytest ignores commad line argument when adding in pytest_cmdline_preparse

[BeKl92]

Pytest version 6.2.3:

This works:

def pytest_cmdline_preparse(args):
    args[:] = ["--verbose"] + args
    args[:] = ["--color=yes"] + args
    args[:] = ["--tb=short"] + args

This does not work (still show warning in command line)

def pytest_cmdline_preparse(args):
    args[:] = ["-W ignore::pytest.PytestUnknownMarkWarning"] + args
    args[:] = ["-W ignore::DeprecationWarning"] + args

calling pytest from command line and give "-W ignore::DeprecationWarning" it is working as expected (all DeprecationWarning will be ignored). But adding it to cmdline_preparse function nothing will be ignored.

The code above worked with pytest 5.0.0 as we have used it until upgrade.

[RonnyPfannschmidt]

its not yet clear what changed between then and now (the code directly invoking this hasn't)

a fair warning, the hook is actually deprecated, but we don't communicate that yet (it was deprecated before pytest had warnings support), i'll add a task to actually schedule its removal

[BeKl92]

Thanks, i have tried to use the suggested function instead (pytest_load_initial_conftests), but as the documentation say it will not be called within conftest.py (where i actually use the preparse function).

I have found this issue which describe a similar problem: #5024

[BeKl92]

Here i found the difference between pytest 5.0.0 and 6.2.3
comparing warnings.py from site-packages_pytest\warnings.py function catch_warnings_for_item

in older version:
cmdline_filters = config.getoption("pythonwarnings") or []

in new version:
cmdline_filters = config.known_args_namespace.pythonwarnings or []

args from preparse or e.g. pytest_load_initial_conftests (same problem here) function are added to the config options and will never be checked in catch_warnings_for_item.

Is this a bug? As it is not possible anymore to ignore warnings using a hook function.

[RonnyPfannschmidt]

hmm, im leaning towards bug - cc @nicoddemus

[asottile]

there's one other issue with your code as well, there should be separate argument (though it's insufficient to fix the problem you're seeing):

def pytest_cmdline_preparse(args):
    args[:] = ["-W", "ignore::pytest.PytestUnknownMarkWarning"] + args
    args[:] = ["-W", "ignore::DeprecationWarning"] + args