[Python-checkins] bpo-32751: Wait for task cancel in asyncio.wait_for() when timeout <= 0 (#21895)
Elvis Pranskevichus
webhook-mailer at python.org
Wed Aug 26 12:42:53 EDT 2020
https://github.com/python/cpython/commit/c517fc712105c8e5930cb42baaebdbe37fc3e15f
commit: c517fc712105c8e5930cb42baaebdbe37fc3e15f
branch: master
author: Elvis Pranskevichus <elvis at magic.io>
committer: GitHub <noreply at github.com>
date: 2020-08-26T09:42:22-07:00
summary:
bpo-32751: Wait for task cancel in asyncio.wait_for() when timeout <= 0 (#21895)
When I was fixing bpo-32751 back in GH-7216 I missed the case when
*timeout* is zero or negative. This takes care of that.
Props to @aaliddell for noticing the inconsistency.
files:
A Misc/NEWS.d/next/Library/2020-08-15-15-50-12.bpo-32751.85je5X.rst
M Lib/asyncio/tasks.py
M Lib/test/test_asyncio/test_tasks.py
diff --git a/Lib/asyncio/tasks.py b/Lib/asyncio/tasks.py
index c37f0e1387980..7ecec9638489d 100644
--- a/Lib/asyncio/tasks.py
+++ b/Lib/asyncio/tasks.py
@@ -445,8 +445,13 @@ async def wait_for(fut, timeout, *, loop=None):
if fut.done():
return fut.result()
- fut.cancel()
- raise exceptions.TimeoutError()
+ await _cancel_and_wait(fut, loop=loop)
+ try:
+ fut.result()
+ except exceptions.CancelledError as exc:
+ raise exceptions.TimeoutError() from exc
+ else:
+ raise exceptions.TimeoutError()
waiter = loop.create_future()
timeout_handle = loop.call_later(timeout, _release_waiter, waiter)
diff --git a/Lib/test/test_asyncio/test_tasks.py b/Lib/test/test_asyncio/test_tasks.py
index f9db066ce8983..511961c32005a 100644
--- a/Lib/test/test_asyncio/test_tasks.py
+++ b/Lib/test/test_asyncio/test_tasks.py
@@ -1131,6 +1131,9 @@ async def inner():
nonlocal task_done
try:
await asyncio.sleep(0.2)
+ except asyncio.CancelledError:
+ await asyncio.sleep(_EPSILON)
+ raise
finally:
task_done = True
@@ -1145,6 +1148,34 @@ async def inner():
chained = cm.exception.__context__
self.assertEqual(type(chained), asyncio.CancelledError)
+ def test_wait_for_waits_for_task_cancellation_w_timeout_0(self):
+ loop = asyncio.new_event_loop()
+ self.addCleanup(loop.close)
+
+ task_done = False
+
+ async def foo():
+ async def inner():
+ nonlocal task_done
+ try:
+ await asyncio.sleep(10)
+ except asyncio.CancelledError:
+ await asyncio.sleep(_EPSILON)
+ raise
+ finally:
+ task_done = True
+
+ inner_task = self.new_task(loop, inner())
+ await asyncio.sleep(_EPSILON)
+ await asyncio.wait_for(inner_task, timeout=0)
+
+ with self.assertRaises(asyncio.TimeoutError) as cm:
+ loop.run_until_complete(foo())
+
+ self.assertTrue(task_done)
+ chained = cm.exception.__context__
+ self.assertEqual(type(chained), asyncio.CancelledError)
+
def test_wait_for_reraises_exception_during_cancellation(self):
loop = asyncio.new_event_loop()
self.addCleanup(loop.close)
diff --git a/Misc/NEWS.d/next/Library/2020-08-15-15-50-12.bpo-32751.85je5X.rst b/Misc/NEWS.d/next/Library/2020-08-15-15-50-12.bpo-32751.85je5X.rst
new file mode 100644
index 0000000000000..c172ce5d9e948
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2020-08-15-15-50-12.bpo-32751.85je5X.rst
@@ -0,0 +1,3 @@
+When cancelling the task due to a timeout, :meth:`asyncio.wait_for` will now
+wait until the cancellation is complete also in the case when *timeout* is
+<= 0, like it does with positive timeouts.
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