source/blender/blenkernel/BKE_customdata.h

@@ -282,6 +282,7 @@ bool CustomData_has_layer(const struct CustomData *data, int type);
  * Returns the number of layers with this type.
  */
 int CustomData_number_of_layers(const struct CustomData *data, int type);
+int CustomData_number_of_anonymous_layers(const struct CustomData *data, int type);
 int CustomData_number_of_layers_typemask(const struct CustomData *data, eCustomDataMask mask);
 
 /**

source/blender/blenkernel/intern/customdata.cc

@@ -2991,6 +2991,20 @@ int CustomData_number_of_layers(const CustomData *data, const int type)
   return number;
 }
 
+int CustomData_number_of_anonymous_layers(const CustomData *data, const int type)
+{
+  int number = 0;
+
+  for (int i = 0; i < data->totlayer; i++) {
+    if (data->layers[i].type == type && data->layers[i].anonymous_id != nullptr) {
+      number++;
+    }
+  }
+
+  return number;
+}
+
+
 int CustomData_number_of_layers_typemask(const CustomData *data, const eCustomDataMask mask)
 {
   int number = 0;

source/blender/makesrna/intern/rna_mesh_utils.h

@@ -8,13 +8,14 @@
 
 /* Macros to help reduce code clutter in rna_mesh.c */
 
-/* Define the accessors for a basic CustomDataLayer collection */
+
+/* Define the accessors for a basic CustomDataLayer collection, skipping anonymous layers */
 #define DEFINE_CUSTOMDATA_LAYER_COLLECTION(collection_name, customdata_type, layer_type) \
   /* check */ \
   static int rna_##collection_name##_check(CollectionPropertyIterator *UNUSED(iter), void *data) \
   { \
     CustomDataLayer *layer = (CustomDataLayer *)data; \
-    return (layer->type != layer_type); \
+    return (layer->anonymous_id != NULL || layer->type != layer_type); \
   } \
   /* begin */ \
   static void rna_Mesh_##collection_name##s_begin(CollectionPropertyIterator *iter, \
@@ -37,7 +38,7 @@
   static int rna_Mesh_##collection_name##s_length(PointerRNA *ptr) \
   { \
     CustomData *data = rna_mesh_##customdata_type(ptr); \
-    return data ? CustomData_number_of_layers(data, layer_type) : 0; \
+    return data ? CustomData_number_of_layers(data, layer_type) - CustomData_number_of_anonymous_layers(data, layer_type) : 0; \
   } \
   /* index range */ \
   static void rna_Mesh_##collection_name##_index_range( \
@@ -45,10 +46,11 @@
   { \
     CustomData *data = rna_mesh_##customdata_type(ptr); \
     *min = 0; \
-    *max = data ? CustomData_number_of_layers(data, layer_type) - 1 : 0; \
+    *max = data ? CustomData_number_of_layers(data, layer_type) - CustomData_number_of_anonymous_layers(data, layer_type) - 1 : 0; \
     *max = MAX2(0, *max); \
   }
 
+
 /* Define the accessors for special CustomDataLayers in the collection
  * (active, render, clone, stencil, etc) */
 #define DEFINE_CUSTOMDATA_LAYER_COLLECTION_ACTIVEITEM( \