Fixed CancelScope's delayed cancellation system (#132)

src/easynetwork_asyncio/tasks.py

@@ -145,7 +145,6 @@ class CancelScope(AbstractCancelScope):
         "__state",
         "__cancel_called",
         "__cancelled_caught",
-        "__task_cancelling",
         "__deadline",
         "__timeout_handle",
         "__delayed_cancellation_on_enter",
@@ -160,7 +159,6 @@ def __init__(self, *, deadline: float = math.inf) -> None:
         self.__state: _ScopeState = _ScopeState.CREATED
         self.__cancel_called: bool = False
         self.__cancelled_caught: bool = False
-        self.__task_cancelling: int = 0
         self.__deadline: float = math.inf
         self.__timeout_handle: asyncio.TimerHandle | None = None
         self.reschedule(deadline)
@@ -180,7 +178,6 @@ def __enter__(self) -> Self:
             raise RuntimeError("CancelScope entered twice")
 
         self.__host_task = current_task = TaskUtils.current_asyncio_task()
-        self.__task_cancelling = current_task.cancelling()
 
         current_task_scope = self.__current_task_scope_dict
         if current_task not in current_task_scope:
@@ -218,13 +215,15 @@ def __exit__(self, exc_type: type[BaseException] | None, exc_val: BaseException
         if self.__cancel_called:
             task_cancelling = host_task.uncancel()
             if isinstance(exc_val, asyncio.CancelledError):
-                self.__cancelled_caught = task_cancelling <= self.__task_cancelling or self.__cancellation_id() in exc_val.args
+                self.__cancelled_caught = self.__cancellation_id() in exc_val.args
 
             delayed_task_cancel = self.__delayed_task_cancel_dict.get(host_task, None)
             if delayed_task_cancel is not None and delayed_task_cancel.message == self.__cancellation_id():
                 del self.__delayed_task_cancel_dict[host_task]
                 delayed_task_cancel.handle.cancel()
+                delayed_task_cancel = None
 
+            if delayed_task_cancel is None:
                 for cancel_scope in self._inner_to_outer_task_scopes(host_task):
                     if cancel_scope.__cancel_called:
                         self._reschedule_delayed_task_cancel(host_task, cancel_scope.__cancellation_id())

tests/functional_test/test_async/test_backend/test_asyncio_backend.py

@@ -1240,6 +1240,91 @@ async def coroutine() -> None:
 
         await event_loop.create_task(coroutine())
 
+    @pytest.mark.xfail(raises=asyncio.CancelledError, reason="Task.cancel() cannot be erased", strict=True)
+    async def test____cancel_shielded_coroutine____scope_cancellation_edge_case_3(
+        self,
+        event_loop: asyncio.AbstractEventLoop,
+        backend: AsyncIOBackend,
+    ) -> None:
+        async def coroutine() -> None:
+            current_task = asyncio.current_task()
+            assert current_task is not None
+
+            with backend.move_on_after(0) as inner_scope:
+                pass
+
+            await backend.coro_yield()
+
+            assert inner_scope.cancel_called()
+
+            assert not inner_scope.cancelled_caught()
+
+        await event_loop.create_task(coroutine())
+
+    async def test____cancel_shielded_coroutine____scope_cancellation_edge_case_4(
+        self,
+        event_loop: asyncio.AbstractEventLoop,
+        backend: AsyncIOBackend,
+    ) -> None:
+        async def coroutine() -> None:
+            current_task = asyncio.current_task()
+            assert current_task is not None
+
+            outer_scope = backend.open_cancel_scope()
+            inner_scope = backend.open_cancel_scope()
+            with outer_scope:
+                outer_scope.cancel()
+
+                await backend.ignore_cancellation(backend.sleep(0.1))
+
+                with inner_scope:
+                    inner_scope.cancel()
+
+                await backend.coro_yield()
+
+            await backend.coro_yield()
+
+            assert outer_scope.cancel_called()
+            assert inner_scope.cancel_called()
+
+            assert not inner_scope.cancelled_caught()
+            assert outer_scope.cancelled_caught()
+
+        await event_loop.create_task(coroutine())
+
+    async def test____cancel_shielded_coroutine____scope_cancellation_edge_case_5(
+        self,
+        event_loop: asyncio.AbstractEventLoop,
+        backend: AsyncIOBackend,
+    ) -> None:
+        async def coroutine() -> None:
+            current_task = asyncio.current_task()
+            assert current_task is not None
+
+            outer_scope = backend.open_cancel_scope()
+            inner_scope = backend.open_cancel_scope()
+            with outer_scope:
+                with inner_scope:
+                    inner_scope.cancel()
+
+                    await backend.cancel_shielded_coro_yield()
+
+                    outer_scope.cancel()
+
+                    await backend.cancel_shielded_coro_yield()
+
+                await backend.coro_yield()
+
+            await backend.coro_yield()
+
+            assert outer_scope.cancel_called()
+            assert inner_scope.cancel_called()
+
+            assert not inner_scope.cancelled_caught()
+            assert outer_scope.cancelled_caught()
+
+        await event_loop.create_task(coroutine())
+
     async def test____ignore_cancellation____do_not_reschedule_if_inner_task_cancelled_itself(
         self,
         event_loop: asyncio.AbstractEventLoop,