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GH-95899: fix asyncio.Runner to call set_event_loop once #95900

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Merged
gvanrossum merged 2 commits into from
Aug 15, 2022
Merged

GH-95899: fix asyncio.Runner to call set_event_loop once #95900

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b6beea4
fix asyncio.Runner call set_event_loop once
kumaraditya303 Aug 11, 2022
843b612
📜🤖 Added by blurb_it.
blurb-it[bot] Aug 11, 2022
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fix asyncio.Runner call set_event_loop once
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@kumaraditya303
kumaraditya303 authored Aug 11, 2022
commit b6beea48c98ae65b4cb52d02539b6725e109fd37
8 changes: 5 additions & 3 deletions Lib/asyncio/runners.py
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Original file line number Diff line number Diff line change
Expand Up @@ -114,8 +114,6 @@ def run(self, coro, *, context=None):

self._interrupt_count = 0
try:
if self._set_event_loop:
events.set_event_loop(self._loop)
return self._loop.run_until_complete(task)
except exceptions.CancelledError:
if self._interrupt_count > 0:
Expand All @@ -136,7 +134,11 @@ def _lazy_init(self):
return
if self._loop_factory is None:
self._loop = events.new_event_loop()
self._set_event_loop = True
if not self._set_event_loop:
# Call set_event_loop only once to avoid calling
# attach_loop multiple times on child watchers
events.set_event_loop(self._loop)
self._set_event_loop = True
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else:
self._loop = self._loop_factory()
if self._debug is not None:
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14 changes: 14 additions & 0 deletions Lib/test/test_asyncio/test_runners.py
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Expand Up @@ -455,6 +455,20 @@ async def coro():
):
runner.run(coro())

def test_set_event_loop_called_once(self):
# See https://github.com/python/cpython/issues/95736
async def coro():
pass

policy = asyncio.get_event_loop_policy()
policy.set_event_loop = mock.Mock()
runner = asyncio.Runner()
runner.run(coro())
runner.run(coro())

self.assertEqual(1, policy.set_event_loop.call_count)
runner.close()


if __name__ == '__main__':
unittest.main()