Only clear restored entity names when the update provides no names

homeassistant/components/bluetooth/passive_update_processor.py

@@ -165,15 +165,17 @@ class PassiveBluetoothDataUpdate[_T]:
                 if current.get(key, UNDEFINED) != data:
                     changed_entity_keys.add(key)
                     current[key] = data  # type: ignore[assignment]
-        # A key present in the update without a name means the integration
-        # does not name that entity; clear any stale name restored from storage.
-        for key in new_data.entity_data.keys() | new_data.entity_descriptions.keys():
-            if (
-                key not in new_data.entity_names
-                and self.entity_names.get(key) is not None
+        # An update without any names means the integration does not name its
+        # entities; clear stale names restored from storage for the updated keys.
+        # Updates that provide names for only some keys are left untouched since
+        # the missing names may be provided by other partial updates.
+        if not new_data.entity_names:
+            for key in (
+                new_data.entity_data.keys() | new_data.entity_descriptions.keys()
             ):
-                changed_entity_keys.add(key)
-                self.entity_names[key] = None
+                if self.entity_names.get(key) is not None:
+                    changed_entity_keys.add(key)
+                    self.entity_names[key] = None
         # If the device changed we don't need to return the changed
         # entity keys as all entities will be updated
         return None if device_change else changed_entity_keys

tests/components/bluetooth/test_passive_update_processor.py

@@ -2029,3 +2029,17 @@ def test_update_clears_names_missing_from_the_update() -> None:
         temperature_key: "Custom name",
         pressure_key: "Pressure",
     }
+
+    update_with_partial_names = PassiveBluetoothDataUpdate(
+        devices={None: DeviceInfo(name="Test Device")},
+        entity_descriptions={temperature_key: temperature_description},
+        entity_names={pressure_key: "Pressure"},
+        entity_data={temperature_key: 15.5, pressure_key: 1234},
+    )
+
+    # An update naming only some keys does not clear the other names
+    assert data.update(update_with_partial_names) == set()
+    assert data.entity_names == {
+        temperature_key: "Custom name",
+        pressure_key: "Pressure",
+    }