allow inheriting EditorPlugin

Author: rune-scape

editor/editor_node.cpp

@@ -4043,6 +4043,7 @@ void EditorNode::set_addon_plugin_enabled(const String &p_addon, bool p_enabled,
 	Ref<Script> scr; // We need to save it for creating "ep" below.
 
 	// Only try to load the script if it has a name. Else, the plugin has no init script.
+	EditorPlugin *ep = nullptr;
 	if (script_path.length() > 0) {
 		script_path = addon_path.get_base_dir().path_join(script_path);
 		// We should not use the cached version on startup to prevent a script reload
@@ -4077,10 +4078,15 @@ void EditorNode::set_addon_plugin_enabled(const String &p_addon, bool p_enabled,
 			show_warning(vformat(TTR("Unable to load addon script from path: '%s'. Script is not in tool mode."), script_path));
 			return;
 		}
+
+		Object *obj = ClassDB::instantiate(scr->get_instance_base_type());
+		ep = Object::cast_to<EditorPlugin>(obj);
+		ERR_FAIL_NULL(ep);
+		ep->set_script(scr);
+	} else {
+		ep = memnew(EditorPlugin);
 	}
 
-	EditorPlugin *ep = memnew(EditorPlugin);
-	ep->set_script(scr);
 	ep->set_plugin_version(plugin_version);
 	addon_name_to_plugin[addon_path] = ep;
 	add_editor_plugin(ep, p_config_changed);