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Implement asyncio.Task.__cancel_requested__ #31313

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Implement asyncio.Task.__cancel_requested__ #31313

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d1ea1d3
Implement task.__cancel_requested__ property
asvetlov Feb 13, 2022
26a0f10
Add test
asvetlov Feb 13, 2022
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7 changes: 6 additions & 1 deletion Lib/asyncio/tasks.py
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Original file line number Diff line number Diff line change
Expand Up @@ -109,6 +109,7 @@ def __init__(self, coro, *, loop=None, name=None):
self._fut_waiter = None
self._coro = coro
self._context = contextvars.copy_context()
self.__cancel_requested__ = False

self._loop.call_soon(self.__step, context=self._context)
_register_task(self)
Expand Down Expand Up @@ -201,6 +202,10 @@ def cancel(self, msg=None):
self._log_traceback = False
if self.done():
return False
if self.__cancel_requested__:
# Cancel was requested by previous task.cancel() call
return False
self.__cancel_requested__ = True
if self._fut_waiter is not None:
if self._fut_waiter.cancel(msg=msg):
# Leave self._fut_waiter; it may be a Task that
Expand Down Expand Up @@ -634,7 +639,7 @@ def _ensure_future(coro_or_future, *, loop=None):
loop = events._get_event_loop(stacklevel=4)
try:
return loop.create_task(coro_or_future)
except RuntimeError:
except RuntimeError:
if not called_wrap_awaitable:
coro_or_future.close()
raise
Expand Down
19 changes: 19 additions & 0 deletions Lib/test/test_asyncio/test_tasks.py
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Expand Up @@ -496,6 +496,25 @@ async def run():
# This also distinguishes from the initial has_cycle=None.
self.assertEqual(has_cycle, False)

def test___cancel_requested__(self):
loop = asyncio.new_event_loop()

async def task():
await asyncio.sleep(10)
return 12

try:
t = self.new_task(loop, task())
self.assertFalse(t.__cancel_requested__)
self.assertTrue(t.cancel())
self.assertTrue(t.__cancel_requested__)
self.assertFalse(t.cancel())

with self.assertRaises(asyncio.CancelledError):
loop.run_until_complete(t)
finally:
loop.close()

def test_cancel(self):

def gen():
Expand Down
35 changes: 35 additions & 0 deletions Modules/_asynciomodule.c
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Original file line number Diff line number Diff line change
Expand Up @@ -91,6 +91,7 @@ typedef struct {
PyObject *task_context;
int task_must_cancel;
int task_log_destroy_pending;
int task_cancel_requested;
} TaskObj;

typedef struct {
Expand Down Expand Up @@ -2039,6 +2040,7 @@ _asyncio_Task___init___impl(TaskObj *self, PyObject *coro, PyObject *loop,
Py_CLEAR(self->task_fut_waiter);
self->task_must_cancel = 0;
self->task_log_destroy_pending = 1;
self->task_cancel_requested = 0;
Py_INCREF(coro);
Py_XSETREF(self->task_coro, coro);

Expand Down Expand Up @@ -2141,6 +2143,32 @@ TaskObj_get_fut_waiter(TaskObj *task, void *Py_UNUSED(ignored))
Py_RETURN_NONE;
}

static PyObject *
TaskObj_get_cancel_requested(TaskObj *task, void *Py_UNUSED(ignored))
{
if (task->task_cancel_requested) {
Py_RETURN_TRUE;
}
else {
Py_RETURN_FALSE;
}
}

static int
TaskObj_set_cancel_requested(TaskObj *task, PyObject *val, void *Py_UNUSED(ignored))
{
if (val == NULL) {
PyErr_SetString(PyExc_AttributeError, "cannot delete attribute");
return -1;
}
int is_true = PyObject_IsTrue(val);
if (is_true < 0) {
return -1;
}
task->task_cancel_requested = is_true;
return 0;
}

/*[clinic input]
_asyncio.Task._make_cancelled_error

Expand Down Expand Up @@ -2205,6 +2233,11 @@ _asyncio_Task_cancel_impl(TaskObj *self, PyObject *msg)
Py_RETURN_FALSE;
}

if (self->task_cancel_requested) {
Py_RETURN_FALSE;
}
self->task_cancel_requested = 1;

if (self->task_fut_waiter) {
PyObject *res;
int is_true;
Expand Down Expand Up @@ -2473,6 +2506,8 @@ static PyGetSetDef TaskType_getsetlist[] = {
{"_must_cancel", (getter)TaskObj_get_must_cancel, NULL, NULL},
{"_coro", (getter)TaskObj_get_coro, NULL, NULL},
{"_fut_waiter", (getter)TaskObj_get_fut_waiter, NULL, NULL},
{"__cancel_requested__", (getter)TaskObj_get_cancel_requested,
(setter)TaskObj_set_cancel_requested, NULL},
{NULL} /* Sentinel */
};

Expand Down