fix: Avoid errors in cleanup of async generators when event loop is already closed

check `is_closed()` before calling cleanup methods
and degrade exceptions to warnings during cleanup to avoid problems

Author: minrk

docs/reference/changelog.rst

@@ -2,11 +2,17 @@
 Changelog
 =========
 
+0.25.3 (2025-01-28)
+===================
+- Avoid errors in cleanup of async generators when event loop is already closed `#1040 <https://github.com/pytest-dev/pytest-asyncio/issues/1040>`_
+
+
 0.25.2 (2025-01-08)
 ===================
 
 - Call ``loop.shutdown_asyncgens()`` before closing the event loop to ensure async generators are closed in the same manner as ``asyncio.run`` does `#1034 <https://github.com/pytest-dev/pytest-asyncio/pull/1034>`_
 
+
 0.25.1 (2025-01-02)
 ===================
 - Fixes an issue that caused a broken event loop when a function-scoped test was executed in between two tests with wider loop scope `#950 <https://github.com/pytest-dev/pytest-asyncio/issues/950>`_
@@ -22,7 +28,6 @@ Changelog
 - Propagates `contextvars` set in async fixtures to other fixtures and tests on Python 3.11 and above. `#1008 <https://github.com/pytest-dev/pytest-asyncio/pull/1008>`_
 
 
-
 0.24.0 (2024-08-22)
 ===================
 - BREAKING: Updated minimum supported pytest version to v8.2.0

pytest_asyncio/plugin.py

@@ -1164,10 +1164,14 @@ def _provide_event_loop() -> Iterator[asyncio.AbstractEventLoop]:
     try:
         yield loop
     finally:
-        try:
-            loop.run_until_complete(loop.shutdown_asyncgens())
-        finally:
-            loop.close()
+        # cleanup the event loop if it hasn't been cleaned up already
+        if not loop.is_closed():
+            try:
+                loop.run_until_complete(loop.shutdown_asyncgens())
+            except Exception as e:
+                warnings.warn(f"Error cleaning up asyncio loop: {e}", RuntimeWarning)
+            finally:
+                loop.close()
 
 
 @pytest.fixture(scope="session")

tests/test_event_loop_fixture.py

@@ -80,3 +80,61 @@ async def generator_fn():
     )
     result = pytester.runpytest_subprocess("--asyncio-mode=strict", "-W", "default")
     result.assert_outcomes(passed=1, warnings=0)
+
+
+def test_event_loop_already_closed(
+    pytester: Pytester,
+):
+    pytester.makeini("[pytest]\nasyncio_default_fixture_loop_scope = function")
+    pytester.makepyfile(
+        dedent(
+            """\
+            import asyncio
+            import pytest
+            import pytest_asyncio
+            pytest_plugins = 'pytest_asyncio'
+
+            @pytest_asyncio.fixture
+            async def _event_loop():
+                return asyncio.get_running_loop()
+
+            @pytest.fixture
+            def cleanup_after(_event_loop):
+                yield
+                # fixture has its own cleanup code
+                _event_loop.close()
+
+            @pytest.mark.asyncio
+            async def test_something(cleanup_after):
+                await asyncio.sleep(0.01)
+            """
+        )
+    )
+    result = pytester.runpytest_subprocess("--asyncio-mode=strict", "-W", "default")
+    result.assert_outcomes(passed=1, warnings=0)
+
+
+def test_event_loop_fixture_asyncgen_error(
+    pytester: Pytester,
+):
+    pytester.makeini("[pytest]\nasyncio_default_fixture_loop_scope = function")
+    pytester.makepyfile(
+        dedent(
+            """\
+            import asyncio
+            import pytest
+
+            pytest_plugins = 'pytest_asyncio'
+
+            @pytest.mark.asyncio
+            async def test_something():
+                # mock shutdown_asyncgen failure
+                loop = asyncio.get_running_loop()
+                async def fail():
+                    raise RuntimeError("mock error cleaning up...")
+                loop.shutdown_asyncgens = fail
+            """
+        )
+    )
+    result = pytester.runpytest_subprocess("--asyncio-mode=strict", "-W", "default")
+    result.assert_outcomes(passed=1, warnings=1)