backends/bluezdbus/manager: Cancel the discovery on disconnect to avo…

…id a timeout

If a device disconnects while waiting for the services to be
discovered, the manager will wait forever.
This commit fixes that by throwing an exception in case of a disconnect.

CHANGELOG.rst

@@ -13,6 +13,8 @@ and this project adheres to `Semantic Versioning <https://semver.org/spec/v2.0.0
 Fixed
 -----
 * Fixed crash in Android backend introduced in v0.19.0. Fixes #1085.
+* BlueZ: Cancel the device discovery wait task if the device disconnects in
+  between to avoid a timeout
 
 `0.19.0`_ (2022-10-13)
 ======================

bleak/backends/bluezdbus/manager.py

@@ -665,20 +665,41 @@ async def _wait_condition(
         ):
             return
 
-        event = asyncio.Event()
+        services_discovered_event = asyncio.Event()
+        device_disconnected_event = asyncio.Event()
 
         def callback():
             if (
+                self._properties[device_path][defs.DEVICE_INTERFACE]["Connected"]
+                is False
+            ):
+                device_disconnected_event.set()
+            elif (
                 self._properties[device_path][defs.DEVICE_INTERFACE][property_name]
                 == property_value
             ):
-                event.set()
+                services_discovered_event.set()
 
         self._condition_callbacks.add(callback)
 
         try:
-            # can be canceled
-            await event.wait()
+            services_discovered_wait_task = asyncio.create_task(
+                services_discovered_event.wait()
+            )
+            device_disconnected_wait_task = asyncio.create_task(
+                device_disconnected_event.wait()
+            )
+            done, pending = await asyncio.wait(
+                {services_discovered_wait_task, device_disconnected_wait_task},
+                return_when=asyncio.FIRST_COMPLETED,
+            )
+
+            for p in pending:
+                p.cancel()
+
+            # device disconnected before the completion of the services discovery
+            if device_disconnected_wait_task in done:
+                raise BleakError("failed to discover services, device disconnected")
         finally:
             self._condition_callbacks.remove(callback)