fix: preserve errno if all exceptions have the same errno

src/aiohappyeyeballs/impl.py

@@ -73,7 +73,7 @@ async def start_connection(
         addr_infos = _interleave_addrinfos(addr_infos, interleave)
 
     sock: Optional[socket.socket] = None
-    exceptions: List[List[Exception]] = []
+    exceptions: List[List[OSError]] = []
     if happy_eyeballs_delay is None or single_addr_info:
         # not using happy eyeballs
         for addrinfo in addr_infos:
@@ -99,20 +99,28 @@ async def start_connection(
     if sock is None:
         all_exceptions = [exc for sub in exceptions for exc in sub]
         try:
+            first_exception = all_exceptions[0]
             if len(all_exceptions) == 1:
-                raise all_exceptions[0]
+                raise first_exception
             else:
                 # If they all have the same str(), raise one.
-                model = str(all_exceptions[0])
+                model = str(first_exception)
                 if all(str(exc) == model for exc in all_exceptions):
-                    raise all_exceptions[0]
+                    raise first_exception
                 # Raise a combined exception so the user can see all
                 # the various error messages.
-                raise OSError(
-                    "Multiple exceptions: {}".format(
-                        ", ".join(str(exc) for exc in all_exceptions)
-                    )
+                msg = "Multiple exceptions: {}".format(
+                    ", ".join(str(exc) for exc in all_exceptions)
                 )
+                # If the errno is the same for all exceptions, raise
+                # an OSError with that errno.
+                first_errno = first_exception.errno
+                if all(
+                    isinstance(exc, OSError) and exc.errno == first_errno
+                    for exc in all_exceptions
+                ):
+                    raise OSError(first_errno, msg)
+                raise OSError(msg)
         finally:
             all_exceptions = None  # type: ignore[assignment]
             exceptions = None  # type: ignore[assignment]
@@ -122,12 +130,12 @@ async def start_connection(
 
 async def _connect_sock(
     loop: asyncio.AbstractEventLoop,
-    exceptions: List[List[Exception]],
+    exceptions: List[List[OSError]],
     addr_info: AddrInfoType,
     local_addr_infos: Optional[Sequence[AddrInfoType]] = None,
 ) -> socket.socket:
     """Create, bind and connect one socket."""
-    my_exceptions: list[Exception] = []
+    my_exceptions: list[OSError] = []
     exceptions.append(my_exceptions)
     family, type_, proto, _, address = addr_info
     sock = None

tests/test_impl.py

@@ -1191,9 +1191,10 @@ async def _sock_connect(
 
 @patch_socket
 @pytest.mark.asyncio
-async def test_all_same_exception(
+async def test_all_same_exception_and_same_errno(
     m_socket: ModuleType,
 ) -> None:
+    """Test that all exceptions are the same and have the same errno."""
     mock_socket = mock.MagicMock(
         family=socket.AF_INET,
         type=socket.SOCK_STREAM,
@@ -1256,7 +1257,96 @@ async def _sock_connect(
     # We should get the same exception raised if they are all the same
     with mock.patch.object(loop, "sock_connect", _sock_connect), pytest.raises(
         OSError, match="all fail"
-    ):
+    ) as exc_info:
+        assert (
+            await start_connection(
+                addr_info,
+                happy_eyeballs_delay=0.3,
+                interleave=2,
+                local_addr_infos=local_addr_infos,
+            )
+            == mock_socket
+        )
+
+    assert exc_info.value.errno == 5
+
+    # All calls failed
+    assert create_calls == [
+        ("dead:beef::", 80, 0, 0),
+        ("dead:aaaa::", 80, 0, 0),
+        ("107.6.106.83", 80),
+    ]
+
+
+@patch_socket
+@pytest.mark.asyncio
+async def test_all_same_exception_and_with_different_errno(
+    m_socket: ModuleType,
+) -> None:
+    """Test no errno is set if all OSError have different errno."""
+    mock_socket = mock.MagicMock(
+        family=socket.AF_INET,
+        type=socket.SOCK_STREAM,
+        proto=socket.IPPROTO_TCP,
+        fileno=mock.MagicMock(return_value=1),
+    )
+    create_calls = []
+
+    def _socket(*args, **kw):
+        for attr in kw:
+            setattr(mock_socket, attr, kw[attr])
+        return mock_socket
+
+    async def _sock_connect(
+        sock: socket.socket, address: Tuple[str, int, int, int]
+    ) -> None:
+        create_calls.append(address)
+        raise OSError(len(create_calls), "all fail")
+
+    m_socket.socket = _socket  # type: ignore
+    ipv6_addr_info = (
+        socket.AF_INET6,
+        socket.SOCK_STREAM,
+        socket.IPPROTO_TCP,
+        "",
+        ("dead:beef::", 80, 0, 0),
+    )
+    ipv6_addr_info_2 = (
+        socket.AF_INET6,
+        socket.SOCK_STREAM,
+        socket.IPPROTO_TCP,
+        "",
+        ("dead:aaaa::", 80, 0, 0),
+    )
+    ipv4_addr_info = (
+        socket.AF_INET,
+        socket.SOCK_STREAM,
+        socket.IPPROTO_TCP,
+        "",
+        ("107.6.106.83", 80),
+    )
+    addr_info = [ipv6_addr_info, ipv6_addr_info_2, ipv4_addr_info]
+    local_addr_infos = [
+        (
+            socket.AF_INET6,
+            socket.SOCK_STREAM,
+            socket.IPPROTO_TCP,
+            "",
+            ("::1", 0, 0, 0),
+        ),
+        (
+            socket.AF_INET,
+            socket.SOCK_STREAM,
+            socket.IPPROTO_TCP,
+            "",
+            ("127.0.0.1", 0),
+        ),
+    ]
+    loop = asyncio.get_running_loop()
+    # We should get the same exception raised if they are all the same
+    with mock.patch.object(loop, "sock_connect", _sock_connect), pytest.raises(
+        OSError, match="all fail"
+    ) as exc_info:
         assert (
             await start_connection(
                 addr_info,
@@ -1267,6 +1357,9 @@ async def _sock_connect(
             == mock_socket
         )
 
+    # No errno is set if they are all different
+    assert exc_info.value.errno is None
+
     # All calls failed
     assert create_calls == [
         ("dead:beef::", 80, 0, 0),