[Python-checkins] Taskgroup tweaks (GH-31559)
gvanrossum
webhook-mailer at python.org
Sat Feb 26 11:18:55 EST 2022
https://github.com/python/cpython/commit/edbee56d698ebb4489aa68311f44d104a23f5eb7
commit: edbee56d698ebb4489aa68311f44d104a23f5eb7
branch: main
author: Tin Tvrtković <tinchester at gmail.com>
committer: gvanrossum <gvanrossum at gmail.com>
date: 2022-02-26T08:18:48-08:00
summary:
Taskgroup tweaks (GH-31559)
Now uses .cancel()/.uncancel(), for even fewer broken edge cases.
files:
M Lib/asyncio/taskgroups.py
M Lib/test/test_asyncio/test_taskgroups.py
diff --git a/Lib/asyncio/taskgroups.py b/Lib/asyncio/taskgroups.py
index 756fc551e013d..c3ce94a4dd0a9 100644
--- a/Lib/asyncio/taskgroups.py
+++ b/Lib/asyncio/taskgroups.py
@@ -66,31 +66,28 @@ async def __aexit__(self, et, exc, tb):
self._base_error is None):
self._base_error = exc
- if et is exceptions.CancelledError:
- if self._parent_cancel_requested:
- # Only if we did request task to cancel ourselves
- # we mark it as no longer cancelled.
- self._parent_task.uncancel()
- else:
- propagate_cancellation_error = et
-
- if et is not None and not self._aborting:
- # Our parent task is being cancelled:
- #
- # async with TaskGroup() as g:
- # g.create_task(...)
- # await ... # <- CancelledError
- #
+ if et is not None:
if et is exceptions.CancelledError:
- propagate_cancellation_error = et
-
- # or there's an exception in "async with":
- #
- # async with TaskGroup() as g:
- # g.create_task(...)
- # 1 / 0
- #
- self._abort()
+ if self._parent_cancel_requested and not self._parent_task.uncancel():
+ # Do nothing, i.e. swallow the error.
+ pass
+ else:
+ propagate_cancellation_error = exc
+
+ if not self._aborting:
+ # Our parent task is being cancelled:
+ #
+ # async with TaskGroup() as g:
+ # g.create_task(...)
+ # await ... # <- CancelledError
+ #
+ # or there's an exception in "async with":
+ #
+ # async with TaskGroup() as g:
+ # g.create_task(...)
+ # 1 / 0
+ #
+ self._abort()
# We use while-loop here because "self._on_completed_fut"
# can be cancelled multiple times if our parent task
@@ -118,7 +115,6 @@ async def __aexit__(self, et, exc, tb):
self._on_completed_fut = None
assert self._unfinished_tasks == 0
- self._on_completed_fut = None # no longer needed
if self._base_error is not None:
raise self._base_error
@@ -199,8 +195,7 @@ def _on_task_done(self, task):
})
return
- self._abort()
- if not self._parent_task.cancelling():
+ if not self._aborting and not self._parent_cancel_requested:
# If parent task *is not* being cancelled, it means that we want
# to manually cancel it to abort whatever is being run right now
# in the TaskGroup. But we want to mark parent task as
@@ -219,5 +214,6 @@ def _on_task_done(self, task):
# pass
# await something_else # this line has to be called
# # after TaskGroup is finished.
+ self._abort()
self._parent_cancel_requested = True
self._parent_task.cancel()
diff --git a/Lib/test/test_asyncio/test_taskgroups.py b/Lib/test/test_asyncio/test_taskgroups.py
index 40774a8993e3f..df51528e10793 100644
--- a/Lib/test/test_asyncio/test_taskgroups.py
+++ b/Lib/test/test_asyncio/test_taskgroups.py
@@ -120,7 +120,11 @@ async def runner():
self.assertTrue(t2_cancel)
self.assertTrue(t2.cancelled())
- async def test_taskgroup_05(self):
+ async def test_cancel_children_on_child_error(self):
+ """
+ When a child task raises an error, the rest of the children
+ are cancelled and the errors are gathered into an EG.
+ """
NUM = 0
t2_cancel = False
@@ -165,7 +169,7 @@ async def runner():
self.assertTrue(t2_cancel)
self.assertTrue(runner_cancel)
- async def test_taskgroup_06(self):
+ async def test_cancellation(self):
NUM = 0
@@ -186,10 +190,12 @@ async def runner():
await asyncio.sleep(0.1)
self.assertFalse(r.done())
- r.cancel()
- with self.assertRaises(asyncio.CancelledError):
+ r.cancel("test")
+ with self.assertRaises(asyncio.CancelledError) as cm:
await r
+ self.assertEqual(cm.exception.args, ('test',))
+
self.assertEqual(NUM, 5)
async def test_taskgroup_07(self):
@@ -226,7 +232,7 @@ async def runner():
self.assertEqual(NUM, 15)
- async def test_taskgroup_08(self):
+ async def test_cancellation_in_body(self):
async def foo():
await asyncio.sleep(0.1)
@@ -246,10 +252,12 @@ async def runner():
await asyncio.sleep(0.1)
self.assertFalse(r.done())
- r.cancel()
- with self.assertRaises(asyncio.CancelledError):
+ r.cancel("test")
+ with self.assertRaises(asyncio.CancelledError) as cm:
await r
+ self.assertEqual(cm.exception.args, ('test',))
+
async def test_taskgroup_09(self):
t1 = t2 = None
@@ -699,3 +707,7 @@ async def coro():
async with taskgroups.TaskGroup() as g:
t = g.create_task(coro(), name="yolo")
self.assertEqual(t.get_name(), "yolo")
+
+
+if __name__ == "__main__":
+ unittest.main()
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