fix: ensure the underlying socket is closed on disconnect (#12)

src/dbus_fast/aio/message_bus.py

@@ -4,7 +4,7 @@
 import socket
 from asyncio import Queue
 from copy import copy
-from typing import Optional
+from typing import Any, Optional
 
 from .. import introspection as intr
 from .._private.unmarshaller import Unmarshaller
@@ -24,18 +24,18 @@
 from .proxy_object import ProxyObject
 
 
-def _future_set_exception(fut, exc):
+def _future_set_exception(fut: asyncio.Future, exc: Exception) -> None:
     if fut is not None and not fut.done():
         fut.set_exception(exc)
 
 
-def _future_set_result(fut, result):
+def _future_set_result(fut: asyncio.Future, result: Any) -> None:
     if fut is not None and not fut.done():
         fut.set_result(result)
 
 
 class _MessageWriter:
-    def __init__(self, bus):
+    def __init__(self, bus: "MessageBus") -> None:
         self.messages = Queue()
         self.negotiate_unix_fd = bus._negotiate_unix_fd
         self.bus = bus
@@ -82,7 +82,10 @@ def write_callback(self):
                     # wait for writable
                     return
         except Exception as e:
-            _future_set_exception(self.fut, e)
+            if self.bus._user_disconnect:
+                _future_set_result(self.fut, None)
+            else:
+                _future_set_exception(self.fut, e)
             self.bus._finalize(e)
 
     def buffer_message(self, msg: Message, future=None):
@@ -229,7 +232,7 @@ async def introspect(
         """
         future = self._loop.create_future()
 
-        def reply_handler(reply, err):
+        def reply_handler(reply: Any, err: Exception) -> None:
             if err:
                 _future_set_exception(future, err)
             else:
@@ -436,13 +439,24 @@ async def _authenticate(self):
             if response == "BEGIN":
                 break
 
-    def _create_unmarshaller(self):
+    def disconnect(self):
+        """Disconnect the message bus by closing the underlying connection asynchronously.
+
+        All pending  and future calls will error with a connection error.
+        """
+        super().disconnect()
+        try:
+            self._sock.close()
+        except Exception:
+            logging.warning("could not close socket", exc_info=True)
+
+    def _create_unmarshaller(self) -> Unmarshaller:
         sock = None
         if self._negotiate_unix_fd:
             sock = self._sock
         return Unmarshaller(self._stream, sock)
 
-    def _finalize(self, err=None):
+    def _finalize(self, err: Optional[Exception] = None) -> None:
         try:
             self._loop.remove_reader(self._fd)
         except Exception: