corebluetooth: work around macOS 12 scanner bug

macOS has a bug (feature?) where advertising data is no longer received unless one
or more service UUIDs are given in scanForPeripheralsWithServices:options:.

This implements a new kwarg on `BleakScanner` to allow users to provide
such a list of UUIDs. This commit only implements it in the CoreBluetooth
backend with other backends to follow.

Issue #635.

CHANGELOG.rst

@@ -10,6 +10,12 @@ and this project adheres to `Semantic Versioning <https://semver.org/spec/v2.0.0
 `Unreleased`_
 =============
 
+Added
+-----
+
+* Added ``service_uuids`` kwarg to  ``BleakScanner``. This can be used to work
+  around issue of scanning not working on macOS 12. Issue #635.
+
 Changed
 -------
 

bleak/backends/corebluetooth/CentralManagerDelegate.py

@@ -104,15 +104,17 @@ def __del__(self):
     # User defined functions
 
     @objc.python_method
-    async def start_scan(self, scan_options) -> None:
+    async def start_scan(self, service_uuids) -> None:
         # remove old
         self.devices = {}
-        service_uuids = None
-        if "service_uuids" in scan_options:
-            service_uuids_str = scan_options["service_uuids"]
-            service_uuids = NSArray.alloc().initWithArray_(
-                list(map(CBUUID.UUIDWithString_, service_uuids_str))
+
+        service_uuids = (
+            NSArray.alloc().initWithArray_(
+                list(map(CBUUID.UUIDWithString_, service_uuids))
             )
+            if service_uuids
+            else None
+        )
 
         self.central_manager.scanForPeripheralsWithServices_options_(
             service_uuids, None

bleak/backends/corebluetooth/scanner.py

@@ -2,6 +2,7 @@
 import pathlib
 from typing import Any, Dict, List, Optional
 
+import objc
 from Foundation import NSArray, NSUUID
 from CoreBluetooth import CBPeripheral
 
@@ -25,17 +26,27 @@ class BleakScannerCoreBluetooth(BaseBleakScanner):
     with this, CoreBluetooth utilizes UUIDs for each peripheral. Bleak uses
     this for the BLEDevice address on macOS.
 
-    Keyword Args:
-        timeout (double): The scanning timeout to be used, in case of missing
+    Args:
+        **timeout (double): The scanning timeout to be used, in case of missing
           ``stopScan_`` method.
-
+        **detection_callback (callable or coroutine):
+            Optional function that will be called each time a device is
+            discovered or advertising data has changed.
+        **service_uuids (List[str]):
+            Optional list of service UUIDs to filter on. Only advertisements
+            containing this advertising data will be received. Required on
+            macOS 12 and later.
     """
 
     def __init__(self, **kwargs):
         super(BleakScannerCoreBluetooth, self).__init__(**kwargs)
         self._identifiers: Optional[Dict[NSUUID, Dict[str, Any]]] = None
         self._manager = CentralManagerDelegate.alloc().init()
         self._timeout: float = kwargs.get("timeout", 5.0)
+        if objc.macos_available(12, 0) and not self._service_uuids:
+            logging.error(
+                "macOS 12 requires non-empty service_uuids kwarg, otherwise no advertisement data will be received"
+            )
 
     async def start(self):
         self._identifiers = {}
@@ -89,7 +100,7 @@ def callback(p: CBPeripheral, a: Dict[str, Any], r: int) -> None:
             self._callback(device, advertisement_data)
 
         self._manager.callbacks[id(self)] = callback
-        await self._manager.start_scan({})
+        await self._manager.start_scan(self._service_uuids)
 
     async def stop(self):
         await self._manager.stop_scan()

bleak/backends/scanner.py

@@ -68,12 +68,28 @@ def __repr__(self) -> str:
 
 
 class BaseBleakScanner(abc.ABC):
-    """Interface for Bleak Bluetooth LE Scanners"""
+    """
+    Interface for Bleak Bluetooth LE Scanners
+
+    Args:
+        **detection_callback (callable or coroutine):
+            Optional function that will be called each time a device is
+            discovered or advertising data has changed.
+        **service_uuids (List[str]):
+            Optional list of service UUIDs to filter on. Only advertisements
+            containing this advertising data will be received. Required on
+            macOS 12 and later.
+    """
 
     def __init__(self, *args, **kwargs):
         super(BaseBleakScanner, self).__init__()
         self._callback: Optional[AdvertisementDataCallback] = None
         self.register_detection_callback(kwargs.get("detection_callback"))
+        self._service_uuids: Optional[List[str]] = (
+            [u.lower() for u in kwargs["service_uuids"]]
+            if "service_uuids" in kwargs
+            else None
+        )
 
     async def __aenter__(self):
         await self.start()

examples/detection_callback.py

@@ -9,20 +9,22 @@
 """
 
 import asyncio
+import logging
+import sys
+
 from bleak import BleakScanner
 from bleak.backends.device import BLEDevice
 from bleak.backends.scanner import AdvertisementData
-import logging
 
-logging.basicConfig()
+logger = logging.getLogger(__name__)
 
 
 def simple_callback(device: BLEDevice, advertisement_data: AdvertisementData):
-    print(device.address, "RSSI:", device.rssi, advertisement_data)
+    logger.info(f"{device.address} RSSI: {device.rssi}, {advertisement_data}")
 
 
-async def main():
-    scanner = BleakScanner()
+async def main(service_uuids):
+    scanner = BleakScanner(service_uuids=service_uuids)
     scanner.register_detection_callback(simple_callback)
 
     while True:
@@ -32,4 +34,9 @@ async def main():
 
 
 if __name__ == "__main__":
-    asyncio.run(main())
+    logging.basicConfig(
+        level=logging.INFO,
+        format="%(asctime)-15s %(name)-8s %(levelname)s: %(message)s",
+    )
+    service_uuids = sys.argv[1:]
+    asyncio.run(main(service_uuids))