logging.captureWarnings does not work in pytest_configure()

[Nikratio]

The setup:

# cat tests/conftest.py 
import logging
import warnings

logging.basicConfig()
logging.captureWarnings(capture=True)

# cat tests/t1_warn.py 
import logging
import warnings

log = logging.getLogger()

def test():
    log.warning('This is a log-warning')
    warnings.warn('This warning should go to logs', UserWarning)
    assert False

This works as expected (warning is captured as log message):

$ python3 -m pytest -s -p no:warnings tests/t1_warn.py
================================================ test session starts ================================================
platform linux -- Python 3.9.2, pytest-6.0.2, py-1.10.0, pluggy-0.13.0
rootdir: /home/nikratio/in-progress/s3ql
plugins: trio-0.7.0, cov-2.10.1
collected 1 item                                                                                                    

tests/t1_warn.py WARNING:root:This is a log-warning
WARNING:py.warnings:/home/nikratio/in-progress/s3ql/tests/t1_warn.py:8: UserWarning: This warning should go to logs
  warnings.warn('This warning should go to logs', UserWarning)

F

===================================================== FAILURES ======================================================
_______________________________________________________ test ________________________________________________________

    def test():
        log.warning('This is a log-warning')
        warnings.warn('This warning should go to logs', UserWarning)
>       assert False
E       assert False

tests/t1_warn.py:9: AssertionError
------------------------------------------------- Captured log call -------------------------------------------------
WARNING  root:t1_warn.py:7 This is a log-warning
WARNING  py.warnings:warnings.py:109 /home/nikratio/in-progress/s3ql/tests/t1_warn.py:8: UserWarning: This warning should go to logs
  warnings.warn('This warning should go to logs', UserWarning)
============================================== short test summary info ==============================================
FAILED tests/t1_warn.py::test - assert False
================================================= 1 failed in 0.05s =================================================

However, if I move the warning configuration into pytest_configure (which I think is the better place for it), it no longer takes effect:

$ cat tests/conftest.py
import logging
import warnings


def pytest_configure(config):
    print('configuring')
    logging.basicConfig()
    logging.captureWarnings(capture=True)

$ python3 -m pytest -s -p no:warnings tests/t1_warn.py
configuring
================================================ test session starts ================================================
platform linux -- Python 3.9.2, pytest-6.0.2, py-1.10.0, pluggy-0.13.0
rootdir: /home/nikratio/in-progress/s3ql
plugins: trio-0.7.0, cov-2.10.1
collected 1 item                                                                                                    

tests/t1_warn.py WARNING:root:This is a log-warning
/home/nikratio/in-progress/s3ql/tests/t1_warn.py:8: UserWarning: This warning should go to logs
  warnings.warn('This warning should go to logs', UserWarning)
F

===================================================== FAILURES ======================================================
_______________________________________________________ test ________________________________________________________

    def test():
        log.warning('This is a log-warning')
        warnings.warn('This warning should go to logs', UserWarning)
>       assert False
E       assert False

tests/t1_warn.py:9: AssertionError
------------------------------------------------- Captured log call -------------------------------------------------
WARNING  root:t1_warn.py:7 This is a log-warning
============================================== short test summary info ==============================================
FAILED tests/t1_warn.py::test - assert False
================================================= 1 failed in 0.05s =================================================

Is this expected behavior? If so, what's the recommended place to configure logging?

[RonnyPfannschmidt]

You should neither configure logging nor warnings as that messes around with global state and in part sabotages pytest correctly setting up logging /warning capture

[Nikratio]

I don't want to use pytest's warning capture, this is why I'm using -p no:warnings. I assume the existence of the option means that this is supported?

(The logging configuration was just here for debugging purposes, removing basicConfig makes no difference to the outcome)

[RonnyPfannschmidt]

In that case a crosscheck is needed

[Nikratio]

Sorry, what do you mean with "a crosscheck is needed"? Is there something I should do?

I have done a bit of digging, and it looks to me as if the -p no:warnings option does not have the intended effect. I modified warnings.py to raise an exception on import and got this:

nikratio@vostro ~/i/s3ql (next) [1]> python3 -m pytest -p no:warnings tests/t1_warn.py
Traceback (most recent call last):
  File "/usr/lib/python3.9/runpy.py", line 197, in _run_module_as_main
    return _run_code(code, main_globals, None,
  File "/usr/lib/python3.9/runpy.py", line 87, in _run_code
    exec(code, run_globals)
  File "/usr/lib/python3/dist-packages/pytest/__main__.py", line 7, in <module>
    raise SystemExit(pytest.console_main())
  File "/usr/lib/python3/dist-packages/_pytest/config/__init__.py", line 180, in console_main
    code = main()
  File "/usr/lib/python3/dist-packages/_pytest/config/__init__.py", line 136, in main
    config = _prepareconfig(args, plugins)
  File "/usr/lib/python3/dist-packages/_pytest/config/__init__.py", line 304, in _prepareconfig
    config = get_config(args, plugins)
  File "/usr/lib/python3/dist-packages/_pytest/config/__init__.py", line 275, in get_config
    pluginmanager.import_plugin(spec)
  File "/usr/lib/python3/dist-packages/_pytest/config/__init__.py", line 689, in import_plugin
    __import__(importspec)
  File "/usr/lib/python3/dist-packages/_pytest/junitxml.py", line 40, in <module>
    from _pytest.warnings import _issue_warning_captured
  File "/usr/lib/python3/dist-packages/_pytest/warnings.py", line 23, in <module>
    raise RuntimeError('not allowed!')
RuntimeError: not allowed!

Could this be the problem?

[RonnyPfannschmidt]

Code imports shouldn't have that effect, i wonder if there is a issue with how unloading /blocking is done