Support Python's ConnectionRefusedError to reject a connection (#1515)

* Support Python's ConnectionRefusedError to reject a connection

* unit tests

docs/server.rst

@@ -246,6 +246,8 @@ a :class:`socketio.exceptions.ConnectionRefusedError` exception can be raised,
 and all of its arguments will be sent to the client with the rejection
 message::
 
+    from socketio.exceptions import ConnectionRefusedError
+
     @sio.event
     def connect(sid, environ, auth):
         raise ConnectionRefusedError('authentication failed')

src/socketio/async_server.py

@@ -561,6 +561,9 @@ class AsyncServer(base_server.BaseServer):
         except exceptions.ConnectionRefusedError as exc:
             fail_reason = exc.error_args
             success = False
+        except ConnectionRefusedError:
+            fail_reason = {"message": "Connection refused by server"}
+            success = False
 
         if success is False:
             if self.always_connect:

src/socketio/server.py

@@ -543,6 +543,9 @@ class Server(base_server.BaseServer):
         except exceptions.ConnectionRefusedError as exc:
             fail_reason = exc.error_args
             success = False
+        except ConnectionRefusedError:
+            fail_reason = {"message": "Connection refused by server"}
+            success = False
 
         if success is False:
             if self.always_connect:

tests/async/test_server.py

@@ -482,6 +482,21 @@ class TestAsyncServer:
             '123', '4{"message":"fail_reason"}')
         assert s.environ == {'123': 'environ'}
 
+    async def test_handle_connect_rejected_with_python_exception(self, eio):
+        eio.return_value.send = mock.AsyncMock()
+        s = async_server.AsyncServer()
+        handler = mock.MagicMock(
+            side_effect=ConnectionRefusedError()
+        )
+        s.on('connect', handler)
+        await s._handle_eio_connect('123', 'environ')
+        await s._handle_eio_message('123', '0')
+        assert not s.manager.is_connected('1', '/')
+        handler.assert_called_once_with('1', 'environ')
+        s.eio.send.assert_awaited_once_with(
+            '123', '4{"message":"Connection refused by server"}')
+        assert s.environ == {'123': 'environ'}
+
     async def test_handle_connect_rejected_with_empty_exception(self, eio):
         eio.return_value.send = mock.AsyncMock()
         s = async_server.AsyncServer()

tests/common/test_server.py

@@ -462,6 +462,20 @@ class TestServer:
         s.eio.send.assert_called_once_with('123', '4{"message":"fail_reason"}')
         assert s.environ == {'123': 'environ'}
 
+    def test_handle_connect_rejected_with_python_exception(self, eio):
+        s = server.Server()
+        handler = mock.MagicMock(
+            side_effect=ConnectionRefusedError()
+        )
+        s.on('connect', handler)
+        s._handle_eio_connect('123', 'environ')
+        s._handle_eio_message('123', '0')
+        assert not s.manager.is_connected('1', '/')
+        handler.assert_called_once_with('1', 'environ')
+        s.eio.send.assert_called_once_with(
+            '123', '4{"message":"Connection refused by server"}')
+        assert s.environ == {'123': 'environ'}
+
     def test_handle_connect_rejected_with_empty_exception(self, eio):
         s = server.Server()
         handler = mock.MagicMock(