Fix: Nodes: propagated menu expanded state to group input

Previously, when a new group input was created from an expanded menu
socket, the expanded flag was not set on the group input.

source/blender/blenkernel/intern/node_tree_interface.cc

@@ -24,6 +24,7 @@
 #include "DNA_node_types.h"
 
 #include "NOD_node_declaration.hh"
+#include "NOD_socket_declarations.hh"
 
 using blender::StringRef;
 
@@ -1157,6 +1158,11 @@ bNodeTreeInterfaceSocket *add_interface_socket_from_node(bNodeTree &ntree,
         description = decl->description;
       }
       SET_FLAG_FROM_TEST(flag, decl->optional_label, NODE_INTERFACE_SOCKET_OPTIONAL_LABEL);
+      if (socket_type == "NodeSocketMenu" && from_sock.type == SOCK_MENU) {
+        if (const auto *menu_decl = dynamic_cast<const nodes::decl::Menu *>(decl)) {
+          SET_FLAG_FROM_TEST(flag, menu_decl->is_expanded, NODE_INTERFACE_SOCKET_MENU_EXPANDED);
+        }
+      }
     }
 
     iosock = ntree.tree_interface.add_socket(name, description, socket_type, flag, nullptr);