parametrize implementation doesn't support infinite generators

[plammens]

Per the pytest documentation, the ids parameter of pytest.mark.parametrize also accepts a (possibly infinite) generator of ids, e.g. (f"foo{i}" for i in itertools.count()). (This has the advantage of not having to care about keeping the lenght of argvalues and ids in sync.) However, pytest_cases's custom managing of ids tries to consume the iterator all at once, hence causing the program to hang indefinitely at the collection stage:

python-pytest-cases/pytest_cases/common_pytest.py

Line 227 in ae942d7

p_ids = list(global_ids)

Reproducible example:

import itertools as itt

import pytest
import pytest_cases


@pytest_cases.fixture()
@pytest.mark.parametrize("x", [1, 2, 3], ids=(f"x{i}" for i in itt.count()))
def my_fixture(x):
    return x

def test_foo(my_fixture):
    pass

This happens even if we replace pytest.mark.parametrize with pytest_cases.parametrize.

[smarie]

Thanks @plammens ! Indeed, good catch. I'll fix this now

[smarie]

Actually could you please provide a reproducible example that enters into this particular case ? Indeed it does not seem to happen
with a basic test:

import itertools
from pytest_cases import parametrize

@parametrize("foo", [1, 2], ids=("foo{%s}" % i for i in itertools.count()))
def test_dummy(foo):
    pass

I guess that it happens with some custom pytest.param or other kind of customization ?

[plammens]

Ah! Should have mentioned that this happened only when parametrizing a fixture (i.e. pytest_cases.fixture on top of pytest.mark.parametrize decorators). I've edited the issue to add a reproducible example.

[smarie]

Thanks @plammens for your reactivity. Fixing this now