BleakClient: Support performing GATT service disocvery after pairing

bleak/__init__.py

@@ -524,7 +524,12 @@ async def pair(
             BleakPairingFailedError:
                 if pairing failed (rejected, wrong pin, etc.)
         """
-        return await self._backend.pair(callbacks, **kwargs)
+        if await self._backend.pair(callbacks, **kwargs):
+            # If services were already discovered during connection procedure, this will return cached
+            # services anyway. If `skip_service_discovery=True` was used, this will perform the discovery.
+            await self._backend.get_services()
+            return True
+        return False
 
     async def unpair(self) -> bool:
         """

examples/pairing_agent.py

@@ -78,10 +78,19 @@ async def main(addr: str, unpair: bool) -> None:
 
     print("pairing...")
 
-    async with BleakClient(device) as client, AgentCallbacks() as callbacks:
+    async with (
+        BleakClient(device) as client,
+        # If the peripheral device sends Slave Security Request immediately upon establishing connection,
+        # the central device shall respond with the pairing request - usually before starting/finishing
+        # service discovery, that is before connect() method normally returns. In such cases the pairing
+        # process usually fails with "Pairing not supported" error - as a workaround,
+        #   BleakClient(device, skip_service_discovery=True) as client,
+        # can be used, which will execute service discovery only after pairing.
+        AgentCallbacks() as callbacks,
+    ):
         try:
             await client.pair(callbacks)
-            print("pairing successful")
+            print(f"pairing successful, {len(client.services.services)} services")
         except BleakPairingCancelledError:
             print("paring was canceled")
         except BleakPairingFailedError: