Added cancel shielding to AsyncFile.aclose()

docs/versionhistory.rst

@@ -13,6 +13,8 @@ This library adheres to `Semantic Versioning 2.0 <http://semver.org/>`_.
   ``Could not create 2 listeners with a consistent port`` when an ephemeral port is
   requested and IPv6 is enabled and the dual-stack path is not available or a specific
   local host name was given
+- Fixed ``AsyncFile`` not shielding against cancellation while closing
+  (`#1314 <https://github.com/agronholm/anyio/pull/1314>`_)
 
 **4.15.1**
 

src/anyio/_core/_fileio.py

@@ -28,6 +28,7 @@
 from .. import to_thread
 from ..abc import AsyncResource
 from ._synchronization import CapacityLimiter
+from ._tasks import CancelScope
 
 if sys.version_info >= (3, 11):
     from typing import Self
@@ -114,7 +115,8 @@ async def __aiter__(self) -> AsyncIterator[AnyStr]:
                 break
 
     async def aclose(self) -> None:
-        return await to_thread.run_sync(self._fp.close, limiter=self._limiter)
+        with CancelScope(shield=True):
+            await to_thread.run_sync(self._fp.close, limiter=self._limiter)
 
     async def read(self, size: int = -1) -> AnyStr:
         return await to_thread.run_sync(self._fp.read, size, limiter=self._limiter)

tests/test_fileio.py

@@ -12,7 +12,14 @@
 from _pytest.fixtures import FixtureRequest
 from _pytest.tmpdir import TempPathFactory
 
-from anyio import AsyncFile, CapacityLimiter, Path, open_file, wrap_file
+from anyio import (
+    AsyncFile,
+    CancelScope,
+    CapacityLimiter,
+    Path,
+    open_file,
+    wrap_file,
+)
 
 
 @pytest.fixture(params=[False, True])
@@ -86,6 +93,14 @@ async def test_wrap_file(
 
         assert path.read_text() == "dummydata"
 
+    async def test_shielded_aclose(self, tmp_path: pathlib.Path) -> None:
+        async with await open_file(tmp_path / "foo", "wb") as f:
+            with CancelScope() as scope:
+                scope.cancel()
+                await f.aclose()
+
+            assert f.closed
+
 
 class TestPath:
     @pytest.fixture