Support setting old material/# properties on MeshInstance3D

scene/3d/mesh_instance_3d.cpp

@@ -50,8 +50,19 @@ bool MeshInstance3D::_set(const StringName &p_name, const Variant &p_value) {
 		return true;
 	}
 
-	if (p_name.operator String().begins_with("surface_material_override/")) {
-		int idx = p_name.operator String().get_slicec('/', 1).to_int();
+	String name = p_name;
+
+#ifndef DISABLE_DEPRECATED
+	if (name.begins_with("material/")) {
+		WARN_DEPRECATED_MSG("This mesh uses an old deprecated parameter name. Consider re-saving this scene in order for it to continue working in future versions." +
+				(is_inside_tree() ? vformat(" Path: \"%s\"", get_path()) : String()));
+	}
+	if (name.begins_with("surface_material_override/") || name.begins_with("material/"))
+#else
+	if (name.begins_with("surface_material_override/"))
+#endif
+	{
+		int idx = name.get_slicec('/', 1).to_int();
 
 		if (idx >= surface_override_materials.size() || idx < 0) {
 			return false;