6.0.0rc1 pytest.fixture mypy error: Value of type "object" is not indexable

[simonjayhawkins]

• a detailed description of the bug or suggestion
• output of pip list from the virtual environment you are using
• pytest and operating system versions
• minimal example if possible

# file: pytest-mypy.py
import pytest


@pytest.fixture(params=[(0, 0), (1, 1)], ids=lambda x: x[0])
def b(request):
    return request.param


def test_b(b):
    pass

$ pytest ~/pytest-mypy.py -vv
=========================================================================== test session starts ============================================================================
platform win32 -- Python 3.8.3, pytest-6.0.0rc1, py-1.9.0, pluggy-0.13.1 -- c:\users\simon\anaconda3\envs\pandas-dev\python.exe
cachedir: .pytest_cache
hypothesis profile 'default' -> database=DirectoryBasedExampleDatabase('C:\\Users\\simon\\pandas\\.hypothesis\\examples')
rootdir: C:\Users\simon
plugins: hypothesis-5.16.3, asyncio-0.12.0, cov-2.10.0, forked-1.1.2, xdist-1.32.0
collected 2 items

..\pytest-mypy.py::test_b[0] PASSED                                                                                                                                   [ 50%]
..\pytest-mypy.py::test_b[1] PASSED                                                                                                                                   [100%]

============================================================================ 2 passed in 0.17s =============================================================================

$ mypy ~/pytest-mypy.py
C:\Users\simon\pytest-mypy.py:4: error: Value of type "object" is not indexable
Found 1 error in 1 file (checked 1 source file)

the type annotation for ids in fixture is

    ids: Optional[
        Union[
            Iterable[Union[None, str, float, int, bool]],
            Callable[[object], Optional[object]],
        ]
    ] = None,

i believe that the Callable should accept Any.

[simonjayhawkins]

This also affects pytest.mark.parametrize

@pytest.mark.parametrize("func", get_is_dtype_funcs(), ids=lambda x: x.__name__)
def test_get_dtype_error_catch(func):

gives error: "object" has no attribute "__name__"; maybe "__ne__" or "__new__"?

the type annotation for _ParametrizeMarkDecorator is also

            ids: Optional[
                Union[
                    Iterable[Union[None, str, float, int, bool]],
                    Callable[[object], Optional[object]],
                ]
            ] = ...,

[simonjayhawkins]

from https://docs.pytest.org/en/stable/fixture.html#parametrizing-fixtures

The above shows how ids can be either a list of strings to use or a function which will be called with the fixture value and then has to return a string to use. In the latter case if the function return None then pytest’s auto-generated ID will be used.

so the return type should be Optional[str]

[simonjayhawkins]

so the return type should be Optional[str]

although maybe safer to use Any (or keep as object), since OP returns int and works OK.

[bluetech]

Yes, I think this should be Any. I sent #7496 for this.