Fix T89400: Possible to delete objects used by overrides of collections.

This should not be allowed in general, added some initial call to check
when user is allowed to delete a data to search for mandatory override
usages...

3 files changed, 37 insertions, 0 deletions

diff --git a/source/blender/blenkernel/BKE_lib_override.h b/source/blender/blenkernel/BKE_lib_override.h
index 20128e2608a..b94a1b33606 100644
--- a/source/blender/blenkernel/BKE_lib_override.h
+++ b/source/blender/blenkernel/BKE_lib_override.h
@@ -173,6 +173,8 @@ void BKE_lib_override_library_main_unused_cleanup(struct Main *bmain);
 void BKE_lib_override_library_update(struct Main *bmain, struct ID *local);
 void BKE_lib_override_library_main_update(struct Main *bmain);
 
+bool BKE_lib_override_library_id_is_user_deletable(struct Main *bmain, struct ID *id);
+
 /* Storage (.blend file writing) part. */
 
 /* For now, we just use a temp main list. */
diff --git a/source/blender/blenkernel/intern/lib_override.c b/source/blender/blenkernel/intern/lib_override.c
index e6ce6734e64..68675e5fc91 100644
--- a/source/blender/blenkernel/intern/lib_override.c
+++ b/source/blender/blenkernel/intern/lib_override.c
@@ -2972,6 +2972,31 @@ void BKE_lib_override_library_main_update(Main *bmain)
   G_MAIN = orig_gmain;
 }
 
+/** In case an ID is used by another liboverride ID, user may not be allowed to delete it. */
+bool BKE_lib_override_library_id_is_user_deletable(struct Main *bmain, struct ID *id)
+{
+  if (!(ID_IS_LINKED(id) || ID_IS_OVERRIDE_LIBRARY(id))) {
+    return true;
+  }
+
+  /* The only strong known case currently are objects used by override collections. */
+  /* TODO: There are most likely other cases... This may need to be addressed in a better way at
+   * some point. */
+  if (GS(id->name) != ID_OB) {
+    return true;
+  }
+  Object *ob = (Object *)id;
+  LISTBASE_FOREACH (Collection *, collection, &bmain->collections) {
+    if (!ID_IS_OVERRIDE_LIBRARY(collection)) {
+      continue;
+    }
+    if (BKE_collection_has_object(collection, ob)) {
+      return false;
+    }
+  }
+  return true;
+}
+
 /**
  * Storage (how to store overriding data into `.blend` files).
  *
diff --git a/source/blender/editors/object/object_add.c b/source/blender/editors/object/object_add.c
index 236246924a9..cc4f2acc346 100644
--- a/source/blender/editors/object/object_add.c
+++ b/source/blender/editors/object/object_add.c
@@ -75,6 +75,7 @@
 #include "BKE_lattice.h"
 #include "BKE_layer.h"
 #include "BKE_lib_id.h"
+#include "BKE_lib_override.h"
 #include "BKE_lib_query.h"
 #include "BKE_lib_remap.h"
 #include "BKE_light.h"
@@ -2015,6 +2016,15 @@ static int object_delete_exec(bContext *C, wmOperator *op)
       continue;
     }
 
+    if (!BKE_lib_override_library_id_is_user_deletable(bmain, &ob->id)) {
+      /* Can this case ever happen? */
+      BKE_reportf(op->reports,
+                  RPT_WARNING,
+                  "Cannot delete object '%s' as it used by override collections",
+                  ob->id.name + 2);
+      continue;
+    }
+
     if (ID_REAL_USERS(ob) <= 1 && ID_EXTRA_USERS(ob) == 0 &&
         BKE_library_ID_is_indirectly_used(bmain, ob)) {
       BKE_reportf(op->reports,