8000 bpo-38248: Fix inconsistent immediate asyncio.Task cancellation by 1st1 · Pull Request #16330 · python/cpython · GitHub
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bpo-38248: Fix inconsistent immediate asyncio.Task cancellation #16330

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Merged
merged 1 commit into from
Sep 25, 2019
Merged

bpo-38248: Fix inconsistent immediate asyncio.Task cancellation #16330

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2 changes: 1 addition & 1 deletion Lib/asyncio/tasks.py
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Original file line number Diff line number Diff line change
Expand Up @@ -284,7 +284,7 @@ def __step(self, exc=None):
if self._must_cancel:
# Task is cancelled right before coro stops.
self._must_cancel = False
super().set_exception(exceptions.CancelledError())
super().cancel()
else:
super().set_result(exc.value)
except exceptions.CancelledError:
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4 changes: 4 additions & 0 deletions Lib/test/test_asyncio/test_tasks.py
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Expand Up @@ -604,9 +604,11 @@ async def task():
return 12

t = self.new_task(loop, task())
self.assertFalse(t.cancelled())
self.assertRaises(
asyncio.CancelledError, loop.run_until_complete, t)
self.assertTrue(t.done())
self.assertTrue(t.cancelled())
self.assertFalse(t._must_cancel) # White-box test.
self.assertFalse(t.cancel())

Expand All @@ -621,9 +623,11 @@ async def task():
return 12

t = self.new_task(loop, task())
self.assertFalse(t.cancelled())
self.assertRaises(
asyncio.CancelledError, loop.run_until_complete, t)
self.assertTrue(t.done())
self.assertTrue(t.cancelled())
self.assertFalse(t._must_cancel) # White-box test.
self.assertFalse(t.cancel())

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1 change: 1 addition & 0 deletions Misc/NEWS.d/next/Library/2019-09-22-13-05-36.bpo-38248.Yo3N_1.rst
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@@ -0,0 +1 @@
asyncio: Fix inconsistent immediate Task cancellation
15 changes: 8 additions & 7 deletions Modules/_asynciomodule.c
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Expand Up @@ -2628,18 +2628,19 @@ 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 */

PyObject *res;
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;
res = future_cancel((FutureObj*)task);
}
else {
res = future_set_result((FutureObj*)task, o);
}
PyObject *res = future_set_result((FutureObj*)task, o);

Py_DECREF(o);

if (res == NULL) {
return NULL;
}
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0