1 files changed, 59 insertions, 0 deletions
diff --git a/Lib/test/test_asyncio/test_base_events.py b/Lib/test/test_asyncio/test_base_events.py
index 2ca5c4c6719..12179eb0c9e 100644
--- a/Lib/test/test_asyncio/test_base_events.py
+++ b/Lib/test/test_asyncio/test_base_events.py
@@ -24,6 +24,10 @@ import warnings
 MOCK_ANY = mock.ANY
 
 
+class CustomError(Exception):
+    pass
+
+
 def tearDownModule():
     asyncio._set_event_loop_policy(None)
 
@@ -1190,6 +1194,36 @@ class BaseEventLoopWithSelectorTests(test_utils.TestCase):
                 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())
@@ -1296,6 +1330,31 @@ class BaseEventLoopWithSelectorTests(test_utils.TestCase):
         self.assertEqual(len(cm.exception.exceptions), 1)
         self.assertIsInstance(cm.exception.exceptions[0], OSError)
 
+    @patch_socket
+    def test_create_connection_connect_non_os_err_close_err(self, m_socket):
+        # Test the case when sock_connect() raises non-OSError exception
+        # and sock.close() raises OSError.
+        async def getaddrinfo(*args, **kw):
+            return [(2, 1, 6, '', ('107.6.106.82', 80))]
+
+        def getaddrinfo_task(*args, **kwds):
+            return self.loop.create_task(getaddrinfo(*args, **kwds))
+
+        self.loop.getaddrinfo = getaddrinfo_task
+        self.loop.sock_connect = mock.Mock()
+        self.loop.sock_connect.side_effect = CustomError
+        sock = mock.Mock()
+        m_socket.socket.return_value = sock
+        sock.close.side_effect = OSError
+
+        coro = self.loop.create_connection(MyProto, 'example.com', 80)
+        self.assertRaises(
+            CustomError, self.loop.run_until_complete, coro)
+
+        coro = self.loop.create_connection(MyProto, 'example.com', 80, all_errors=True)
+        self.assertRaises(
+            CustomError, self.loop.run_until_complete, coro)
+
     def test_create_connection_multiple(self):
         async def getaddrinfo(*args, **kw):
             return [(2, 1, 6, '', ('0.0.0.1', 80)),