diff --git a/Lib/asyncio/base_events.py b/Lib/asyncio/base_events.py index 07ec6de6414ec2..78d20c93a1b43f 100644 --- a/Lib/asyncio/base_events.py +++ b/Lib/asyncio/base_events.py @@ -1164,7 +1164,7 @@ async def create_connection( raise ExceptionGroup("create_connection failed", exceptions) if len(exceptions) == 1: raise exceptions[0] - else: + elif exceptions: # If they all have the same str(), raise one. model = str(exceptions[0]) if all(str(exc) == model for exc in exceptions): @@ -1173,6 +1173,9 @@ async def create_connection( # the various error messages. raise OSError('Multiple exceptions: {}'.format( ', '.join(str(exc) for exc in exceptions))) + else: + # No exceptions were collected, raise a timeout error + raise TimeoutError('create_connection failed') finally: exceptions = None diff --git a/Lib/test/test_asyncio/test_base_events.py b/Lib/test/test_asyncio/test_base_events.py index 3d3459f47c8324..bd67f9425ee4ac 100644 --- a/Lib/test/test_asyncio/test_base_events.py +++ b/Lib/test/test_asyncio/test_base_events.py @@ -1190,6 +1190,36 @@ def getaddrinfo(*args, **kw): self.loop.run_until_complete(coro) self.assertTrue(sock.close.called) + @patch_socket + def test_create_connection_happy_eyeballs_empty_exceptions(self, m_socket): + # See gh-135836: Fix IndexError when Happy Eyeballs algorithm + # results in empty exceptions list + + async def getaddrinfo(*args, **kw): + return [(socket.AF_INET, socket.SOCK_STREAM, 0, '', ('127.0.0.1', 80)), + (socket.AF_INET6, socket.SOCK_STREAM, 0, '', ('::1', 80))] + + def getaddrinfo_task(*args, **kwds): + return self.loop.create_task(getaddrinfo(*args, **kwds)) + + self.loop.getaddrinfo = getaddrinfo_task + + # Mock staggered_race to return empty exceptions list + # This simulates the scenario where Happy Eyeballs algorithm + # cancels all attempts but doesn't properly collect exceptions + with mock.patch('asyncio.staggered.staggered_race') as mock_staggered: + # Return (None, []) - no winner, empty exceptions list + async def mock_race(coro_fns, delay, loop): + return None, [] + mock_staggered.side_effect = mock_race + + coro = self.loop.create_connection( + MyProto, 'example.com', 80, happy_eyeballs_delay=0.1) + + # Should raise TimeoutError instead of IndexError + with self.assertRaisesRegex(TimeoutError, "create_connection failed"): + self.loop.run_until_complete(coro) + def test_create_connection_host_port_sock(self): coro = self.loop.create_connection( MyProto, 'example.com', 80, sock=object()) diff --git a/Misc/NEWS.d/next/Library/2025-06-23-11-04-25.gh-issue-135836.-C-c4v.rst b/Misc/NEWS.d/next/Library/2025-06-23-11-04-25.gh-issue-135836.-C-c4v.rst new file mode 100644 index 00000000000000..f93c9faee5863a --- /dev/null +++ b/Misc/NEWS.d/next/Library/2025-06-23-11-04-25.gh-issue-135836.-C-c4v.rst @@ -0,0 +1 @@ +Fix :exc:`IndexError` in :meth:`asyncio.loop.create_connection` that could occur when the Happy Eyeballs algorithm resulted in an empty exceptions list during connection attempts.