Enable live logging via fixture

[phausamann]

I am dynamically determining whether my tests are called with a debugger attached through the following fixture:

@pytest.fixture()
def debug():
    """Fixture that indicates whether debugger is attached or not."""
    gettrace = getattr(sys, "gettrace", None)

    if gettrace is None:
        return False
    else:
        gettrace_result = gettrace()

    try:
        from coverage.pytracer import PyTracer
        from coverage.tracer import CTracer

        if isinstance(gettrace_result, (CTracer, PyTracer)):
            return False
    except ImportError:
        pass

    return gettrace_result

I would like to emulate the behavior of the --log-cli-level=DEBUG option within this fixture in order to obtain live logging during debugging. Is this possible?

Thanks in advance!

[twmr]

First of all, such a cli-logging fixture would be a great addition to the pytest logging plugin.

I think it is possible to replicate the behavior of the log-cli feature in a
pytest fixture, but integrating it in a proper way into pytest might turn
out to be complicated.

All you need is the catching_logs ctx manager and the log_cli_level and the log_cli_handler.

[twmr]

Here is a minimal example that shows you how you can enable cli-logging within a test

def test_logcal_logcli(pytestconfig):
    from _pytest.logging import catching_logs
    from _pytest.logging import _LiveLoggingStreamHandler
    terminal_reporter = pytestconfig.pluginmanager.get_plugin("terminalreporter")
    capture_manager = pytestconfig.pluginmanager.get_plugin("capturemanager")
    log_cli_handler = _LiveLoggingStreamHandler(terminal_reporter,
                                                capture_manager)

    with catching_logs(log_cli_handler, level=logging.DEBUG):
        logger.debug('dbg')
        logger.error('err')

[phausamann]

Thanks @Thisch, this is extremely helpful. For reference, here's the modified debug fixture that now also enables live debug logging:

@pytest.fixture()
def debug(pytestconfig):
    """Fixture that indicates whether debugger is attached or not.

    Also enables live logging at DEBUG level if in debug mode."""
    import logging

    from _pytest.logging import _LiveLoggingStreamHandler, catching_logs

    # check whether tracer is attached at all
    gettrace = getattr(sys, "gettrace", None)

    if gettrace is None:
        return False
    else:
        gettrace_result = gettrace()

    if not gettrace_result:
        return False

    # check whether tracer is coverage tracer
    try:
        from coverage.pytracer import PyTracer
        from coverage.tracer import CTracer

        if isinstance(gettrace_result, (CTracer, PyTracer)):
            return False
    except ImportError:
        pass

    # set up live logging
    terminal_reporter = pytestconfig.pluginmanager.get_plugin("terminalreporter")
    capture_manager = pytestconfig.pluginmanager.get_plugin("capturemanager")
    log_cli_handler = _LiveLoggingStreamHandler(terminal_reporter, capture_manager)

    with catching_logs(log_cli_handler, level=logging.DEBUG):
        yield True