Considering a simple test which raises a warning and a pytest.ini file:

import warnings

def test_foo():
    warnings.warn(UserWarning('oh no'))

[pytest]
filterwarnings =
    error   

Running with $ pytest -W ignore still makes the warning an error. I believe this is a bug and command-line options should take precedence over ini-options.

(Follow-up from #3945).

In summary the current precedence order is:

1. mark
2. ini file
3. cmdline option

IMHO this should be instead:

1. mark
2. cmdline option
3. ini