Prevent premature closing of scoped event loops

docs/source/reference/changelog.rst

@@ -2,6 +2,11 @@
 Changelog
 =========
 
+0.23.3 (UNRELEASED)
+===================
+- Fixes a bug that caused event loops to be closed prematurely when using async generator fixtures with class scope or wider in a function-scoped test `#708 <https://github.com/pytest-dev/pytest-asyncio/issues/708>`_
+
+
 0.23.2 (2023-12-04)
 ===================
 - Fixes a bug that caused an internal pytest error when collecting .txt files `#703 <https://github.com/pytest-dev/pytest-asyncio/issues/703>`_

pytest_asyncio/plugin.py

@@ -600,6 +600,7 @@ def scoped_event_loop(
         new_loop_policy = event_loop_policy
         with _temporary_event_loop_policy(new_loop_policy):
             loop = asyncio.new_event_loop()
+            loop.__pytest_asyncio = True  # type: ignore[attr-defined]
             asyncio.set_event_loop(loop)
             yield loop
             loop.close()
@@ -749,7 +750,8 @@ def pytest_fixture_setup(
             with warnings.catch_warnings():
                 warnings.simplefilter("ignore", DeprecationWarning)
                 old_loop = policy.get_event_loop()
-            if old_loop is not loop:
+            is_pytest_asyncio_loop = getattr(old_loop, "__pytest_asyncio", False)
+            if old_loop is not loop and not is_pytest_asyncio_loop:
                 old_loop.close()
         except RuntimeError:
             # Either the current event loop has been set to None
@@ -965,6 +967,7 @@ def _session_event_loop(
     new_loop_policy = event_loop_policy
     with _temporary_event_loop_policy(new_loop_policy):
         loop = asyncio.new_event_loop()
+        loop.__pytest_asyncio = True  # type: ignore[attr-defined]
         asyncio.set_event_loop(loop)
         yield loop
         loop.close()

tests/markers/test_module_scope.py

@@ -282,6 +282,36 @@ async def test_runs_in_different_loop_as_fixture(async_fixture):
     result.assert_outcomes(passed=1)
 
 
+def test_allows_combining_module_scoped_asyncgen_fixture_with_function_scoped_test(
+    pytester: Pytester,
+):
+    pytester.makepyfile(
+        dedent(
+            """\
+            import asyncio
+
+            import pytest
+            import pytest_asyncio
+
+            loop: asyncio.AbstractEventLoop
+
+            @pytest_asyncio.fixture(scope="module")
+            async def async_fixture():
+                global loop
+                loop = asyncio.get_running_loop()
+                yield
+
+            @pytest.mark.asyncio(scope="function")
+            async def test_runs_in_different_loop_as_fixture(async_fixture):
+                global loop
+                assert asyncio.get_running_loop() is not loop
+            """
+        ),
+    )
+    result = pytester.runpytest("--asyncio-mode=strict")
+    result.assert_outcomes(passed=1)
+
+
 def test_asyncio_mark_handles_missing_event_loop_triggered_by_fixture(
     pytester: Pytester,
 ):

tests/markers/test_session_scope.py

@@ -350,6 +350,37 @@ async def test_runs_in_different_loop_as_fixture(async_fixture):
     result.assert_outcomes(passed=1)
 
 
+def test_allows_combining_session_scoped_asyncgen_fixture_with_function_scoped_test(
+    pytester: Pytester,
+):
+    pytester.makepyfile(
+        __init__="",
+        test_mixed_scopes=dedent(
+            """\
+            import asyncio
+
+            import pytest
+            import pytest_asyncio
+
+            loop: asyncio.AbstractEventLoop
+
+            @pytest_asyncio.fixture(scope="session")
+            async def async_fixture():
+                global loop
+                loop = asyncio.get_running_loop()
+                yield
+
+            @pytest.mark.asyncio
+            async def test_runs_in_different_loop_as_fixture(async_fixture):
+                global loop
+                assert asyncio.get_running_loop() is not loop
+            """
+        ),
+    )
+    result = pytester.runpytest("--asyncio-mode=strict")
+    result.assert_outcomes(passed=1)
+
+
 def test_asyncio_mark_handles_missing_event_loop_triggered_by_fixture(
     pytester: Pytester,
 ):