fix: ensure exceptions are logged when no reply is expected (#342)

src/dbus_fast/aio/message_bus.py

@@ -21,7 +21,7 @@
 from ..errors import AuthError
 from ..message import Message
 from ..message_bus import BaseMessageBus, _block_unexpected_reply
-from ..service import ServiceInterface
+from ..service import ServiceInterface, _Method
 from .message_reader import build_message_reader
 from .proxy_object import ProxyObject
 
@@ -423,7 +423,19 @@ async def wait_for_disconnect(self):
         """
         return await self._disconnect_future
 
-    def _make_method_handler(self, interface, method):
+    def _future_exception_no_reply(self, fut: asyncio.Future) -> None:
+        """Log an exception from a future that was not expected."""
+        self._pending_futures.discard(fut)
+        try:
+            fut.result()
+        except asyncio.CancelledError:
+            pass
+        except Exception as e:
+            logging.error("unexpected exception in future", exc_info=e)
+
+    def _make_method_handler(
+        self, interface: "ServiceInterface", method: "_Method"
+    ) -> Callable[[Message, Callable[[Message], None]], None]:
         if not asyncio.iscoroutinefunction(method.fn):
             return super()._make_method_handler(interface, method)
 
@@ -436,15 +448,15 @@ def _coroutine_method_handler(
         ) -> None:
             """A coroutine method handler."""
             args = msg_body_to_args(msg) if msg.unix_fds else msg.body
-            fut = asyncio.ensure_future(method.fn(interface, *args))
+            fut: asyncio.Future = asyncio.ensure_future(method.fn(interface, *args))
             # Hold a strong reference to the future to ensure
             # it is not garbage collected before it is done.
             self._pending_futures.add(fut)
             if (
                 send_reply is _block_unexpected_reply
                 or msg.flags.value & NO_REPLY_EXPECTED_VALUE
             ):
-                fut.add_done_callback(self._pending_futures.discard)
+                fut.add_done_callback(self._future_exception_no_reply)
                 return
 
             # We only create the closure function if we are actually going to reply