1 files changed, 147 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..22ae0ef3581 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)
 
@@ -146,6 +150,29 @@ class BaseEventTests(test_utils.TestCase):
                                                    socket.SOCK_STREAM,
                                                    socket.IPPROTO_TCP))
 
+    def test_interleave_addrinfos(self):
+        self.maxDiff = None
+        SIX_A = (socket.AF_INET6, 0, 0, '', ('2001:db8::1', 1))
+        SIX_B = (socket.AF_INET6, 0, 0, '', ('2001:db8::2', 2))
+        SIX_C = (socket.AF_INET6, 0, 0, '', ('2001:db8::3', 3))
+        SIX_D = (socket.AF_INET6, 0, 0, '', ('2001:db8::4', 4))
+        FOUR_A = (socket.AF_INET, 0, 0, '', ('192.0.2.1', 5))
+        FOUR_B = (socket.AF_INET, 0, 0, '', ('192.0.2.2', 6))
+        FOUR_C = (socket.AF_INET, 0, 0, '', ('192.0.2.3', 7))
+        FOUR_D = (socket.AF_INET, 0, 0, '', ('192.0.2.4', 8))
+
+        addrinfos = [SIX_A, SIX_B, SIX_C, FOUR_A, FOUR_B, FOUR_C, FOUR_D, SIX_D]
+        expected = [SIX_A, FOUR_A, SIX_B, FOUR_B, SIX_C, FOUR_C, SIX_D, FOUR_D]
+
+        self.assertEqual(expected, base_events._interleave_addrinfos(addrinfos))
+
+        expected_fafc_2 = [SIX_A, SIX_B, FOUR_A, SIX_C, FOUR_B, SIX_D, FOUR_C, FOUR_D]
+        self.assertEqual(
+            expected_fafc_2,
+            base_events._interleave_addrinfos(addrinfos, first_address_family_count=2),
+        )
+
+
 
 class BaseEventLoopTests(test_utils.TestCase):
 
@@ -1049,6 +1076,71 @@ class BaseEventLoopTests(test_utils.TestCase):
             test_utils.run_briefly(self.loop)
             self.assertTrue(status['finalized'])
 
+    @unittest.skipUnless(socket_helper.IPV6_ENABLED, 'no IPv6 support')
+    @patch_socket
+    def test_create_connection_happy_eyeballs(self, m_socket):
+
+        class MyProto(asyncio.Protocol):
+            pass
+
+        async def getaddrinfo(*args, **kw):
+            return [(socket.AF_INET6, 0, 0, '', ('2001:db8::1', 1)),
+                    (socket.AF_INET, 0, 0, '', ('192.0.2.1', 5))]
+
+        async def sock_connect(sock, address):
+            if address[0] == '2001:db8::1':
+                await asyncio.sleep(1)
+            sock.connect(address)
+
+        loop = asyncio.new_event_loop()
+        loop._add_writer = mock.Mock()
+        loop._add_writer = mock.Mock()
+        loop._add_reader = mock.Mock()
+        loop.getaddrinfo = getaddrinfo
+        loop.sock_connect = sock_connect
+
+        coro = loop.create_connection(MyProto, 'example.com', 80, happy_eyeballs_delay=0.3)
+        transport, protocol = loop.run_until_complete(coro)
+        try:
+            sock = transport._sock
+            sock.connect.assert_called_with(('192.0.2.1', 5))
+        finally:
+            transport.close()
+            test_utils.run_briefly(loop)  # allow transport to close
+            loop.close()
+
+    @patch_socket
+    def test_create_connection_happy_eyeballs_ipv4_only(self, m_socket):
+
+        class MyProto(asyncio.Protocol):
+            pass
+
+        async def getaddrinfo(*args, **kw):
+            return [(socket.AF_INET, 0, 0, '', ('192.0.2.1', 5)),
+                    (socket.AF_INET, 0, 0, '', ('192.0.2.2', 6))]
+
+        async def sock_connect(sock, address):
+            if address[0] == '192.0.2.1':
+                await asyncio.sleep(1)
+            sock.connect(address)
+
+        loop = asyncio.new_event_loop()
+        loop._add_writer = mock.Mock()
+        loop._add_writer = mock.Mock()
+        loop._add_reader = mock.Mock()
+        loop.getaddrinfo = getaddrinfo
+        loop.sock_connect = sock_connect
+
+        coro = loop.create_connection(MyProto, 'example.com', 80, happy_eyeballs_delay=0.3)
+        transport, protocol = loop.run_until_complete(coro)
+        try:
+            sock = transport._sock
+            sock.connect.assert_called_with(('192.0.2.2', 6))
+        finally:
+            transport.close()
+            test_utils.run_briefly(loop)  # allow transport to close
+            loop.close()
+
 
 class MyProto(asyncio.Protocol):
     done = None
@@ -1190,6 +1282,36 @@ 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 +1418,31 @@ 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)),