Don't allow updating a device to have no connections or identifiers (#120603)

* Don't allow updating a device to have no connections or identifiers

* Move check to the top of the function

homeassistant/helpers/device_registry.py

@@ -869,6 +869,11 @@ class DeviceRegistry(BaseRegistry[dict[str, list[dict[str, Any]]]]):
                 )
             add_config_entry = config_entry
 
+        if not new_connections and not new_identifiers:
+            raise HomeAssistantError(
+                "A device must have at least one of identifiers or connections"
+            )
+
         if merge_connections is not UNDEFINED and new_connections is not UNDEFINED:
             raise HomeAssistantError(
                 "Cannot define both merge_connections and new_connections"

tests/helpers/test_device_registry.py

@@ -3052,3 +3052,22 @@ async def test_primary_config_entry(
         model="model",
     )
     assert device.primary_config_entry == mock_config_entry_1.entry_id
+
+
+async def test_update_device_no_connections_or_identifiers(
+    hass: HomeAssistant,
+    device_registry: dr.DeviceRegistry,
+) -> None:
+    """Test updating a device clearing connections and identifiers."""
+    mock_config_entry = MockConfigEntry(domain="mqtt", title=None)
+    mock_config_entry.add_to_hass(hass)
+
+    device = device_registry.async_get_or_create(
+        config_entry_id=mock_config_entry.entry_id,
+        connections={(dr.CONNECTION_NETWORK_MAC, "12:34:56:AB:CD:EF")},
+        identifiers={("bridgeid", "0123")},
+    )
+    with pytest.raises(HomeAssistantError):
+        device_registry.async_update_device(
+            device.id, new_connections=set(), new_identifiers=set()
+        )