capsys fixture cannot be used with a session-scoped fixture

[st-pasha]

I have the following use-case: there is a class Auditor, which helps gather statistic about certain tests. This class is used via a fixture:

@pytest.fixture(scope="session")
def auditor():
    aud = Auditor()
    yield aud
    aud.display_summary()

The intention being that some tests would use this fixture, report their results to the Auditor singleton, and in the end of the testing session a report table is produced.

Unfortunately, currently this works only with -s flag, because otherwise all output is captured. Ideally I'd like to write the fixture function as

@pytest.fixture(scope="session")
def auditor(capsys):
    aud = Auditor()
    yield aud
    with capsys.disabled():
        aud.display_summary()

however doing so produces an error that capsys is a function-scope capture and cannot be used with a session-scope fixture.

I believe there should be a way to provide a session-scoped variant of capsys, so that it can be used from user-defined session-scoped fixtures.

[RonnyPfannschmidt]

while i also bevel there is a way, i'm reasonably certain that its not possible to do it sensible with the current capture system internals as such this one requires a larger internal rewrite

but i wouldn't mind to be shown wrong on this one

[st-pasha]

I found that the following hack does the trick:

@pytest.fixture(scope="session")
def auditor():
    aud = Auditor()
    yield aud
    # The property `aud.capsys` is assigned in the test below
    with aud.capsys.disabled():
        aud.display_summary()

def test_fake(capsys, auditor):
    # This test doesn't test anything, but merely saves `capsys` fixture
    # as a property of the auditor.
    auditor.capsys = capsys

Of course, there is still the problem that test_fake may be skipped (if the user wants to run pytest on a subset of tests only).

[L-F-Escobar]

This doesnt help me at all.

I have a session scoped function in conftest.py (root) which outputs data to the console for viewing. I have to pass the -s flag to see that data right now, but that produces tons of extra system data which pollutes the output.

I am attempting to pass capsys into the session scoped function but that produce a ScopeMismatch error.

Is there no way to print to console in a session scoped function without the -s command?

[tyll]

I was missing this feature as well. I am using warnings.warn() now which might even be better in my use case. See nmstate/nmstate#588 for details if interested.

[miso-belica]

@tyll can you explain it more, please? From what I understand pytest captures the warnings too and shows them at the end but I would like to inform the user that some long-running process is running right away so he/she should be patient.

[RonnyPfannschmidt]

https://pypi.org/project/pytest-print/ is a pytest plugin that provides a fixture which handles the details

[k4nar]

I've found the following workaround, which seems to be working fine:

@pytest.fixture(scope=session)
def my_fixture(request):
    capmanager = request.config.pluginmanager.getplugin("capturemanager")

    ...

    with capmanager.global_and_fixture_disabled():
        print_something()

    ...

However if capsys could be a session fixture by default that would be much easier :) .