Fix a deadlock when services are missing (#165)

When services are missing we want to clear the cache and disconnect so we can try again to get the services.

The code that triggered the disconnect when services were missing tried to obtain the connection lock but the lock was already held which resulted in a deadlock.

Author: bdraco

switchbot/devices/device.py

@@ -270,6 +270,7 @@ async def _ensure_connected(self):
                 ble_device_callback=lambda: self._device,
             )
             _LOGGER.debug("%s: Connected; RSSI: %s", self.name, self.rssi)
+            self._client = client
 
             try:
                 self._resolve_characteristics(client.services)
@@ -282,10 +283,10 @@ async def _ensure_connected(self):
                     exc_info=True,
                 )
                 await client.clear_cache()
-                await self._execute_forced_disconnect()
+                self._cancel_disconnect_timer()
+                await self._execute_disconnect_with_lock()
                 raise
 
-            self._client = client
             self._reset_disconnect_timer()
             await self._start_notify()
 
@@ -358,18 +359,28 @@ async def _execute_timed_disconnect(self) -> None:
 
     async def _execute_disconnect(self) -> None:
         """Execute disconnection."""
+        _LOGGER.debug("%s: Executing disconnect", self.name)
         async with self._connect_lock:
-            if self._disconnect_timer:  # If the timer was reset, don't disconnect
-                return
-            client = self._client
-            self._expected_disconnect = True
-            self._client = None
-            self._read_char = None
-            self._write_char = None
-            if client and client.is_connected:
-                _LOGGER.debug("%s: Disconnecting", self.name)
-                await client.disconnect()
-                _LOGGER.debug("%s: Disconnect completed", self.name)
+            await self._execute_disconnect_with_lock()
+
+    async def _execute_disconnect_with_lock(self) -> None:
+        """Execute disconnection while holding the lock."""
+        assert self._connect_lock.locked(), "Lock not held"
+        _LOGGER.debug("%s: Executing disconnect with lock", self.name)
+        if self._disconnect_timer:  # If the timer was reset, don't disconnect
+            _LOGGER.debug("%s: Skipping disconnect as timer reset", self.name)
+            return
+        client = self._client
+        self._expected_disconnect = True
+        self._client = None
+        self._read_char = None
+        self._write_char = None
+        if client and client.is_connected:
+            _LOGGER.debug("%s: Disconnecting", self.name)
+            await client.disconnect()
+            _LOGGER.debug("%s: Disconnect completed", self.name)
+        else:
+            _LOGGER.debug("%s: Already disconnected", self.name)
 
     async def _send_command_locked(self, key: str, command: bytes) -> bytes:
         """Send command to device and read response."""