fix: ensure discovered_devices returns an empty list for offline scan…

…ners (#35)

src/habluetooth/scanner.py

@@ -4,7 +4,7 @@
 import asyncio
 import logging
 import platform
-from typing import TYPE_CHECKING, Any, Coroutine, Iterable
+from typing import Any, Coroutine, Iterable
 
 import bleak
 from bleak import BleakError
@@ -166,17 +166,17 @@ def _create_background_task(self, coro: Coroutine[Any, Any, None]) -> None:
     @property
     def discovered_devices(self) -> list[BLEDevice]:
         """Return a list of discovered devices."""
-        if TYPE_CHECKING:
-            assert self.scanner is not None
+        if not self.scanner:
+            return []
         return self.scanner.discovered_devices
 
     @property
     def discovered_devices_and_advertisement_data(
         self,
     ) -> dict[str, tuple[BLEDevice, AdvertisementData]]:
         """Return a list of discovered devices and advertisement data."""
-        if TYPE_CHECKING:
-            assert self.scanner is not None
+        if not self.scanner:
+            return {}
         return self.scanner.discovered_devices_and_advertisement_data
 
     @property

tests/test_scanner.py

@@ -55,6 +55,15 @@ def manager():
     return manager
 
 
+@pytest.mark.asyncio
+async def test_empty_data_no_scanner() -> None:
+    """Test we handle empty data."""
+    scanner = HaScanner(BluetoothScanningMode.ACTIVE, "hci0", "AA:BB:CC:DD:EE:FF")
+    scanner.async_setup()
+    assert scanner.discovered_devices == []
+    assert scanner.discovered_devices_and_advertisement_data == {}
+
+
 @pytest.mark.asyncio
 @pytest.mark.skipif("platform.system() != 'Linux'")
 async def test_dbus_socket_missing_in_container(