Fix T76710: objects get lost in linked/overridden collections

Right now:
- drag-drop in the Outliner prevents dropping inside linked collections
- drag-drop in the Outliner allows dropping inside overridden
collections (should not be the case)
- `Object Properties` > `Collections` panel allows to add to overridden
collection (should not be the case)
- `Object Properties` > `Collections` panel filters out non-local
collections (so adding to linked collections is forbidden)
- `bpy collection.objects.link()` allows to add to linked collections
(should not be the case)
- `bpy collection.objects.link()` allows to add to overridden
collections (should not be the case)

While this might be supported in the future for overriden collections,
these cases should not be allowed atm. since objects get lost on file
reload.

Note: for the case of the `Object Properties` > `Collections` panel,
this could be improved further to filter out overridden collections as
well.

Reviewers: mont29, brecht

Subscribers:

1 files changed, 16 insertions, 0 deletions

diff --git a/source/blender/editors/object/object_collection.c b/source/blender/editors/object/object_collection.c
index 7554c4efeda..0822697d265 100644
--- a/source/blender/editors/object/object_collection.c
+++ b/source/blender/editors/object/object_collection.c
@@ -481,6 +481,22 @@ static int collection_link_exec(bContext *C, wmOperator *op)
     return OPERATOR_FINISHED;
   }
 
+  /* Currently this should not be allowed (might be supported in the future though...). */
+  if (ID_IS_OVERRIDE_LIBRARY(&collection->id)) {
+    BKE_report(op->reports,
+               RPT_ERROR,
+               "Could not add the collection because it is overridden.");
+    return OPERATOR_CANCELLED;
+  }
+  /* Linked collections are already checked for by using RNA_collection_local_itemf
+   * but operator can be called without invoke */
+  if (ID_IS_LINKED(&collection->id)) {
+    BKE_report(op->reports,
+               RPT_ERROR,
+               "Could not add the collection because it is linked.");
+    return OPERATOR_CANCELLED;
+  }
+
   /* Adding object to collection which is used as dupli-collection for self is bad idea.
    *
    * It is also  bad idea to add object to collection which is in collection which