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[3.7] bpo-35125: remove inner callback on outer cancellation in asyncio shield (GH-10340) #13167

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Merged
miss-islington merged 1 commit into from
May 7, 2019
Merged

[3.7] bpo-35125: remove inner callback on outer cancellation in asyncio shield (GH-10340) #13167

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10 changes: 8 additions & 2 deletions Lib/asyncio/tasks.py
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Original file line number Diff line number Diff line change
Expand Up @@ -774,7 +774,7 @@ def shield(arg, *, loop=None):
loop = futures._get_loop(inner)
outer = loop.create_future()

def _done_callback(inner):
def _inner_done_callback(inner):
if outer.cancelled():
if not inner.cancelled():
# Mark inner's result as retrieved.
Expand All @@ -790,7 +790,13 @@ def _done_callback(inner):
else:
outer.set_result(inner.result())

inner.add_done_callback(_done_callback)

def _outer_done_callback(outer):
if not inner.done():
inner.remove_done_callback(_inner_done_callback)

inner.add_done_callback(_inner_done_callback)
outer.add_done_callback(_outer_done_callback)
return outer


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11 changes: 10 additions & 1 deletion Lib/test/test_asyncio/test_tasks.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1745,14 +1745,23 @@ def test_shield_exception(self):
test_utils.run_briefly(self.loop)
self.assertIs(outer.exception(), exc)

def test_shield_cancel(self):
def test_shield_cancel_inner(self):
inner = self.new_future(self.loop)
outer = asyncio.shield(inner)
test_utils.run_briefly(self.loop)
inner.cancel()
test_utils.run_briefly(self.loop)
self.assertTrue(outer.cancelled())

def test_shield_cancel_outer(self):
inner = self.new_future(self.loop)
outer = asyncio.shield(inner)
test_utils.run_briefly(self.loop)
outer.cancel()
test_utils.run_briefly(self.loop)
self.assertTrue(outer.cancelled())
self.assertEqual(0, 0 if outer._callbacks is None else len(outer._callbacks))

def test_shield_shortcut(self):
fut = self.new_future(self.loop)
fut.set_result(42)
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1 change: 1 addition & 0 deletions Misc/NEWS.d/next/Library/2019-02-15-17-18-50.bpo-35125.h0xk0f.rst
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@@ -0,0 +1 @@
Asyncio: Remove inner callback on outer cancellation in shield