How Can Request.param Be Annotated In Indirect Parametrization?

In the Indirect parametrization example I want to type hint request.param indicating a specific type, a str for example. The problem is since the argument to fixt must be the reque

Solution 1:

As of now (version 6.2), pytest doesn't provide any type hint for the param attribute. If you need to just type param regardless of the rest of FixtureRequest fields and methods, you can inline your own impl stub:

from typing import TYPE_CHECKING


if TYPE_CHECKING:
    classFixtureRequest:
        param: str
else:
    from typing importAnyFixtureRequest= Any


@pytest.fixture
def fixt(request: FixtureRequest) -> str:
    return request.param * 3

If you want to extend existing typing of FixtureRequest, the stubbing gets somewhat more complex:

from typing importTYPE_CHECKINGifTYPE_CHECKING:
    from pytest importFixtureRequestas __FixtureRequest
    classFixtureRequest(__FixtureRequest):
        param: str
else:
    from pytest importFixtureRequest@pytest.fixture
def fixt(request: FixtureRequest) -> str:
    return request.param * 3

Ideally, pytest would allow generic param types in FixtureRequest, e.g.

P = TypeVar("P")  # generic param typeclassFixtureRequest(Generic[P]):
    def__init__(self, param: P, ...):
        ...

You would then just do

from pytest import FixtureRequest

@pytest.fixture
def fixt(request: FixtureRequest[str]) -> str:
    return request.param * 3

Not sure, however, whether this typing is agreeable with the current pytest's codebase - I guess it was omitted for a reason...