Don't crash when a cancelled app tries to close the stream

src/hypercorn/asyncio/task_group.py

@@ -27,10 +27,15 @@ async def _handle(
     try:
         await app(scope, receive, send, sync_spawn, call_soon)
     except asyncio.CancelledError:
+        try:
+            await send(None)
+        except Exception:
+            pass
         raise
     except Exception:
         await config.log.exception("Error in ASGI Framework")
-    finally:
+        await send(None)
+    else:
         await send(None)
 
 

src/hypercorn/trio/task_group.py

@@ -27,6 +27,10 @@ async def _handle(
     try:
         await app(scope, receive, send, sync_spawn, call_soon)
     except trio.Cancelled:
+        try:
+            await send(None)
+        except Exception:
+            pass
         raise
     except BaseExceptionGroup as error:
         _, other_errors = error.split(trio.Cancelled)
@@ -37,7 +41,8 @@ async def _handle(
             raise
     except Exception:
         await config.log.exception("Error in ASGI Framework")
-    finally:
+        await send(None)
+    else:
         await send(None)
 
 

tests/asyncio/test_task_group.py

@@ -43,3 +43,30 @@ async def _error_app(scope: Scope, receive: Callable, send: Callable) -> None:
     async with TaskGroup(event_loop) as task_group:
         await task_group.spawn_app(ASGIWrapper(_error_app), Config(), http_scope, app_queue.put)
     assert (await app_queue.get()) is None
+
+
+@pytest.mark.asyncio
+async def test_handle_cancel_ignores_send_failure(http_scope: HTTPScope) -> None:
+    from hypercorn.asyncio.task_group import _handle
+
+    async def _hang_app(scope: Scope, receive: Callable, send: Callable) -> None:
+        await asyncio.Event().wait()
+
+    async def _failing_send(message: object) -> None:
+        raise AssertionError("cannot call write() after reset()")
+
+    task = asyncio.create_task(
+        _handle(
+            ASGIWrapper(_hang_app),
+            Config(),
+            http_scope,
+            None,  # type: ignore[arg-type]
+            _failing_send,
+            None,  # type: ignore[arg-type]
+            None,  # type: ignore[arg-type]
+        )
+    )
+    await asyncio.sleep(0)
+    task.cancel()
+    with pytest.raises(asyncio.CancelledError):
+        await task