From 3dc7c52a9f4fb83be3e26e31e2c7cd9dc1cb41a2 Mon Sep 17 00:00:00 2001 From: INADA Naoki Date: Thu, 11 May 2017 21:56:42 +0900 Subject: bpo-30048: asyncio: fix Task.cancel() was ignored. (GH-1546) when there are no more `await` or `yield (from)` before return in coroutine, cancel was ignored. example: async def coro(): asyncio.Task.current_task().cancel() return 42 ... res = await coro() # should raise CancelledError (cherry picked from commit 991adca012f5e106c2d4040ce619c696ba6f9c46) --- Lib/asyncio/tasks.py | 7 ++++++- Lib/test/test_asyncio/test_tasks.py | 18 ++++++++++++++++++ Misc/NEWS | 3 +++ Modules/_asynciomodule.c | 12 ++++++++++++ 4 files changed, 39 insertions(+), 1 deletion(-) diff --git a/Lib/asyncio/tasks.py b/Lib/asyncio/tasks.py index f91e70a..d7867d1 100644 --- a/Lib/asyncio/tasks.py +++ b/Lib/asyncio/tasks.py @@ -180,7 +180,12 @@ class Task(futures.Future): else: result = coro.throw(exc) except StopIteration as exc: - self.set_result(exc.value) + if self._must_cancel: + # Task is cancelled right before coro stops. + self._must_cancel = False + self.set_exception(futures.CancelledError()) + else: + self.set_result(exc.value) except futures.CancelledError: super().cancel() # I.e., Future.cancel(self). except Exception as exc: diff --git a/Lib/test/test_asyncio/test_tasks.py b/Lib/test/test_asyncio/test_tasks.py index 4f05319..5462c80 100644 --- a/Lib/test/test_asyncio/test_tasks.py +++ b/Lib/test/test_asyncio/test_tasks.py @@ -588,6 +588,24 @@ class BaseTaskTests: self.assertFalse(t._must_cancel) # White-box test. self.assertFalse(t.cancel()) + def test_cancel_at_end(self): + """coroutine end right after task is cancelled""" + loop = asyncio.new_event_loop() + self.set_event_loop(loop) + + @asyncio.coroutine + def task(): + t.cancel() + self.assertTrue(t._must_cancel) # White-box test. + return 12 + + t = self.new_task(loop, task()) + self.assertRaises( + asyncio.CancelledError, loop.run_until_complete, t) + self.assertTrue(t.done()) + self.assertFalse(t._must_cancel) # White-box test. + self.assertFalse(t.cancel()) + def test_stop_while_run_in_complete(self): def gen(): diff --git a/Misc/NEWS b/Misc/NEWS index 58b8d26..b6b4054 100644 --- a/Misc/NEWS +++ b/Misc/NEWS @@ -36,6 +36,9 @@ Core and Builtins Library ------- +- bpo-30048: Fixed ``Task.cancel()`` can be ignored when the task is + running coroutine and the coroutine returned without any more ``await``. + - bpo-30298: Weaken the condition of deprecation warnings for inline modifiers. Now allowed several subsequential inline modifiers at the start of the pattern (e.g. ``'(?i)(?s)...'``). In verbose mode whitespaces and comments diff --git a/Modules/_asynciomodule.c b/Modules/_asynciomodule.c index a77ff96..75327fa 100644 --- a/Modules/_asynciomodule.c +++ b/Modules/_asynciomodule.c @@ -1984,6 +1984,16 @@ task_step_impl(TaskObj *task, PyObject *exc) if (_PyGen_FetchStopIterationValue(&o) == 0) { /* The error is StopIteration and that means that the underlying coroutine has resolved */ + if (task->task_must_cancel) { + // Task is cancelled right before coro stops. + Py_DECREF(o); + task->task_must_cancel = 0; + et = asyncio_CancelledError; + Py_INCREF(et); + ev = NULL; + tb = NULL; + goto set_exception; + } PyObject *res = future_set_result((FutureObj*)task, o); Py_DECREF(o); if (res == NULL) { @@ -2001,6 +2011,8 @@ task_step_impl(TaskObj *task, PyObject *exc) /* Some other exception; pop it and call Task.set_exception() */ PyErr_Fetch(&et, &ev, &tb); + +set_exception: assert(et); if (!ev || !PyObject_TypeCheck(ev, (PyTypeObject *) et)) { PyErr_NormalizeException(&et, &ev, &tb); -- cgit v0.12