Support parameterized fixtures in doctests

[staadecker]

I'd like to be able to run all my doctests twice (once for each of my backends). This is essentially equivalent to a use case already described in your documentation. Here's what I'd like to do:

# conftest.py

@pytest.fixture(autouse=True, params=["backend_1", "backend_2"])
def _setup_before_each_test(request):
    my_library.global_setting_1 = request.param

This works fine for normal pytests (yay 🎉) but fails on doctests.

The requested fixture has no parameter defined for test:
    src/pyoframe/_arithmetic.py::pyoframe._arithmetic._get_dimensions
Requested fixture '_setup_before_each_test' defined in:
conftest.py:7
Requested here:
.venv\lib\site-packages\_pytest\fixtures.py:697

I was surprised considering the pytest documentation on doctests says "fixtures marked as autouse are supported".

Any suggested workarounds? What would be needed to add support for parameterized autouse fixtures in doctests?

Details on the error

Note that the error (as explained in #4666) seems to stem from the fact that doctest doesn't detect the parameterized fixture during collection which means that it fails at runtime (as it doesn't know which backend to use).

[RonnyPfannschmidt]

I'm -1 on adding this to core

Fancy doctest addons should be investigated in plugins

[nicoddemus]

Strange, it warrants investigation... if we already support autouse fixtures, I would expect parametrized fixtures to work too.

[RonnyPfannschmidt]

Doctest collection doesn't invoke test generation

[nicoddemus]

Hmm right.

At least we should document this limitation then.