2 files changed, 27 insertions, 0 deletions
diff --git a/source/blender/makesrna/RNA_access.h b/source/blender/makesrna/RNA_access.h
index 5441cf44ac9..eb25733a88a 100644
--- a/source/blender/makesrna/RNA_access.h
+++ b/source/blender/makesrna/RNA_access.h
@@ -1117,6 +1117,11 @@ void RNA_property_collection_next(CollectionPropertyIterator *iter);
 void RNA_property_collection_skip(CollectionPropertyIterator *iter, int num);
 void RNA_property_collection_end(CollectionPropertyIterator *iter);
 int RNA_property_collection_length(PointerRNA *ptr, PropertyRNA *prop);
+/**
+ * Return true when `RNA_property_collection_length(ptr, prop) == 0`,
+ * without having to iterate over items in the collection (needed for some kinds of collections).
+ */
+bool RNA_property_collection_is_empty(PointerRNA *ptr, PropertyRNA *prop);
 int RNA_property_collection_lookup_index(PointerRNA *ptr, PropertyRNA *prop, PointerRNA *t_ptr);
 int RNA_property_collection_lookup_int(PointerRNA *ptr,
                                        PropertyRNA *prop,
@@ -1445,6 +1450,7 @@ void RNA_pointer_add(PointerRNA *ptr, const char *name);
 
 void RNA_collection_begin(PointerRNA *ptr, const char *name, CollectionPropertyIterator *iter);
 int RNA_collection_length(PointerRNA *ptr, const char *name);
+bool RNA_collection_is_empty(PointerRNA *ptr, const char *name);
 void RNA_collection_add(PointerRNA *ptr, const char *name, PointerRNA *r_value);
 void RNA_collection_clear(PointerRNA *ptr, const char *name);
 
diff --git a/source/blender/makesrna/intern/rna_access.c b/source/blender/makesrna/intern/rna_access.c
index 8189dc6b16f..6c3b46c4408 100644
--- a/source/blender/makesrna/intern/rna_access.c
+++ b/source/blender/makesrna/intern/rna_access.c
@@ -3753,6 +3753,16 @@ int RNA_property_collection_length(PointerRNA *ptr, PropertyRNA *prop)
   return length;
 }
 
+bool RNA_property_collection_is_empty(PointerRNA *ptr, PropertyRNA *prop)
+{
+  BLI_assert(RNA_property_type(prop) == PROP_COLLECTION);
+  CollectionPropertyIterator iter;
+  RNA_property_collection_begin(ptr, prop, &iter);
+  bool test = iter.valid;
+  RNA_property_collection_end(&iter);
+  return !test;
+}
+
 /* This helper checks whether given collection property itself is editable (we only currently
  * support a limited set of operations, insertion of new items, and re-ordering of those new items
  * exclusively). */
@@ -6417,6 +6427,17 @@ int RNA_collection_length(PointerRNA *ptr, const char *name)
   return 0;
 }
 
+bool RNA_collection_is_empty(PointerRNA *ptr, const char *name)
+{
+  PropertyRNA *prop = RNA_struct_find_property(ptr, name);
+
+  if (prop) {
+    return RNA_property_collection_is_empty(ptr, prop);
+  }
+  printf("%s: %s.%s not found.\n", __func__, ptr->type->identifier, name);
+  return false;
+}
+
 bool RNA_property_is_set_ex(PointerRNA *ptr, PropertyRNA *prop, bool use_ghost)
 {
   prop = rna_ensure_property(prop);