Fix FixtureFunction TypeAlias and TypeVars

docs/reference/changelog.rst

@@ -5,6 +5,8 @@ Changelog
 0.26.0 (UNRELEASED)
 ===================
 - Adds configuration option that sets default event loop scope for all testss `#793 <https://github.com/pytest-dev/pytest-asyncio/issues/793>`_
+- Improved type annotations for ``pytest_asyncio.fixture`` `#1045 <https://github.com/pytest-dev/pytest-asyncio/pull/1045>`_
+- Added ``typing-extensions`` as additional dependency for Python ``<3.10`` `#1045 <https://github.com/pytest-dev/pytest-asyncio/pull/1045>`_
 
 
 0.25.2 (2025-01-08)

pyproject.toml

@@ -38,6 +38,7 @@ dynamic = [
 
 dependencies = [
   "pytest>=8.2,<9",
+  "typing-extensions>=4.12; python_version<'3.10'",
 ]
 optional-dependencies.docs = [
   "sphinx>=5.3",

pytest_asyncio/plugin.py

@@ -9,6 +9,7 @@
 import functools
 import inspect
 import socket
+import sys
 import warnings
 from asyncio import AbstractEventLoop, AbstractEventLoopPolicy
 from collections.abc import (
@@ -53,17 +54,17 @@
     StashKey,
 )
 
+if sys.version_info >= (3, 10):
+    from typing import ParamSpec
+else:
+    from typing_extensions import ParamSpec
+
+
 _ScopeName = Literal["session", "package", "module", "class", "function"]
 _T = TypeVar("_T")
-
-SimpleFixtureFunction = TypeVar(
-    "SimpleFixtureFunction", bound=Callable[..., Awaitable[object]]
-)
-FactoryFixtureFunction = TypeVar(
-    "FactoryFixtureFunction", bound=Callable[..., AsyncIterator[object]]
-)
-FixtureFunction = Union[SimpleFixtureFunction, FactoryFixtureFunction]
-FixtureFunctionMarker = Callable[[FixtureFunction], FixtureFunction]
+_R = TypeVar("_R", bound=Union[Awaitable[Any], AsyncIterator[Any]])
+_P = ParamSpec("_P")
+FixtureFunction = Callable[_P, _R]
 
 
 class PytestAsyncioError(Exception):
@@ -117,7 +118,7 @@ def pytest_addoption(parser: Parser, pluginmanager: PytestPluginManager) -> None
 
 @overload
 def fixture(
-    fixture_function: FixtureFunction,
+    fixture_function: FixtureFunction[_P, _R],
     *,
     scope: _ScopeName | Callable[[str, Config], _ScopeName] = ...,
     loop_scope: _ScopeName | None = ...,
@@ -129,7 +130,7 @@ def fixture(
         | None
     ) = ...,
     name: str | None = ...,
-) -> FixtureFunction: ...
+) -> FixtureFunction[_P, _R]: ...
 
 
 @overload
@@ -146,22 +147,25 @@ def fixture(
         | None
     ) = ...,
     name: str | None = None,
-) -> FixtureFunctionMarker: ...
+) -> Callable[[FixtureFunction[_P, _R]], FixtureFunction[_P, _R]]: ...
 
 
 def fixture(
-    fixture_function: FixtureFunction | None = None,
+    fixture_function: FixtureFunction[_P, _R] | None = None,
     loop_scope: _ScopeName | None = None,
     **kwargs: Any,
-) -> FixtureFunction | FixtureFunctionMarker:
+) -> (
+    FixtureFunction[_P, _R]
+    | Callable[[FixtureFunction[_P, _R]], FixtureFunction[_P, _R]]
+):
     if fixture_function is not None:
         _make_asyncio_fixture_function(fixture_function, loop_scope)
         return pytest.fixture(fixture_function, **kwargs)
 
     else:
 
         @functools.wraps(fixture)
-        def inner(fixture_function: FixtureFunction) -> FixtureFunction:
+        def inner(fixture_function: FixtureFunction[_P, _R]) -> FixtureFunction[_P, _R]:
             return fixture(fixture_function, loop_scope=loop_scope, **kwargs)
 
         return inner
@@ -679,7 +683,7 @@ def pytest_pycollect_makeitem_convert_async_functions_to_subclass(
 
 # A stack used to push package-scoped loops during collection of a package
 # and pop those loops during collection of a Module
-__package_loop_stack: list[FixtureFunctionMarker | FixtureFunction] = []
+__package_loop_stack: list[Callable[..., Any]] = []
 
 
 @pytest.hookimpl