Autoupdates for all children if the item type has changed (fixes #3636).

CHANGELOG

@@ -17,6 +17,7 @@ Agenda:
 - New DOCX export of agenda [#3569].
 - Hide closed agenda items in the item slide [#3567].
 - Agenda is now collapsable for a better overview [#3567].
+- Autoupdates for all children if the item type has changed [#3659].
 
 Motions:
 - New export dialog [#3185].

openslides/agenda/views.py

@@ -58,6 +58,30 @@ class ItemViewSet(ListModelMixin, RetrieveModelMixin, UpdateModelMixin, GenericV
             result = False
         return result
 
+    def update(self, *args, **kwargs):
+        """
+        Customized view endpoint to update all children if, the item type has changed.
+        """
+        hidden = self.get_object().type == Item.HIDDEN_ITEM
+
+        result = super().update(*args, **kwargs)
+
+        # update all children, if the item type has changed
+        item = self.get_object()
+        if hidden != (item.type == Item.HIDDEN_ITEM):
+            items_to_update = []
+
+            # rekursively add children to items_to_update
+            def add_item(item):
+                items_to_update.append(item)
+                for child in item.children.all():
+                    add_item(child)
+
+            add_item(item)
+            inform_changed_data(items_to_update)
+
+        return result
+
     @detail_route(methods=['POST', 'PATCH', 'DELETE'])
     def manage_speaker(self, request, pk=None):
         """