Allow TODO entity listeners to handle None state (#166276)

homeassistant/components/todo/__init__.py

@@ -240,7 +240,7 @@ class TodoListEntity(Entity, cached_properties=CACHED_PROPERTIES_WITH_ATTR_):
     """An entity that represents a To-do list."""
 
     _attr_todo_items: list[TodoItem] | None = None
-    _update_listeners: list[Callable[[list[TodoItem]], None]] | None = None
+    _update_listeners: list[Callable[[list[TodoItem] | None], None]] | None = None
 
     @property
     def state(self) -> int | None:
@@ -281,7 +281,7 @@ class TodoListEntity(Entity, cached_properties=CACHED_PROPERTIES_WITH_ATTR_):
     @final
     @callback
     def async_subscribe_updates(
-        self, listener: Callable[[list[TodoItem]], None]
+        self, listener: Callable[[list[TodoItem] | None], None]
     ) -> CALLBACK_TYPE:
         """Subscribe to To-do list item updates."""
         if self._update_listeners is None:
@@ -302,7 +302,12 @@ class TodoListEntity(Entity, cached_properties=CACHED_PROPERTIES_WITH_ATTR_):
         if not self._update_listeners:
             return
 
-        todo_items = [copy.copy(item) for item in self.todo_items or []]
+        todo_items = (
+            [copy.copy(item) for item in self.todo_items]
+            if self.todo_items is not None
+            else None
+        )
+
         for listener in self._update_listeners:
             listener(todo_items)
 
@@ -335,14 +340,13 @@ async def websocket_handle_subscribe_todo_items(
         return
 
     @callback
-    def todo_item_listener(todo_items: list[TodoItem]) -> None:
+    def todo_item_listener(todo_items: list[TodoItem] | None) -> None:
         """Push updated To-do list items to websocket."""
+        items = [dataclasses.asdict(item) for item in todo_items or []]
         connection.send_message(
             websocket_api.event_message(
                 msg["id"],
-                {
-                    "items": [dataclasses.asdict(item) for item in todo_items],
-                },
+                {"items": items},
             )
         )
 

tests/components/todo/test_init.py

@@ -1239,9 +1239,9 @@ async def test_async_subscribe_updates(
     """Test async_subscribe_updates delivers list updates to listeners."""
     await create_mock_platform(hass, [test_entity])
 
-    received_updates: list[list[TodoItem]] = []
+    received_updates: list[list[TodoItem] | None] = []
 
-    def listener(items: list[TodoItem]) -> None:
+    def listener(items: list[TodoItem] | None) -> None:
         received_updates.append(items)
 
     unsub = test_entity.async_subscribe_updates(listener)
@@ -1277,7 +1277,25 @@ async def test_async_subscribe_updates(
     assert len(items) == 3
     assert items[2].summary == "Item #3"
 
+    # Set items to None and trigger update
+    test_entity._attr_todo_items = None
+    test_entity.async_write_ha_state()
+    assert len(received_updates) == 3
+    assert received_updates[2] is None
+
+    # Add a new item to make it available again and trigger update
+    test_entity._attr_todo_items = [
+        TodoItem(summary="New item", uid="4", status=TodoItemStatus.NEEDS_ACTION)
+    ]
+    test_entity.async_write_ha_state()
+    assert len(received_updates) == 4
+    items = received_updates[3]
+    assert len(items) == 1
+    assert items[0].summary == "New item"
+    assert items[0].uid == "4"
+    assert items[0].status == TodoItemStatus.NEEDS_ACTION
+
     # Unsubscribe and verify no more updates
     unsub()
     test_entity.async_write_ha_state()
-    assert len(received_updates) == 2
+    assert len(received_updates) == 4