Speed up scene group scanning for text scenes

editor/editor_file_system.cpp

@@ -1891,7 +1891,7 @@ void EditorFileSystem::_update_scene_groups() {
 			continue;
 		}
 
-		const HashSet<StringName> scene_groups = _get_scene_groups(path);
+		const HashSet<StringName> scene_groups = PackedScene::get_scene_groups(path);
 		if (!scene_groups.is_empty()) {
 			ProjectSettings::get_singleton()->add_scene_groups_cache(path, scene_groups);
 		}
@@ -1935,12 +1935,6 @@ void EditorFileSystem::_get_all_scenes(EditorFileSystemDirectory *p_dir, HashSet
 	}
 }
 
-HashSet<StringName> EditorFileSystem::_get_scene_groups(const String &p_path) {
-	Ref<PackedScene> packed_scene = ResourceLoader::load(p_path);
-	ERR_FAIL_COND_V(packed_scene.is_null(), HashSet<StringName>());
-	return packed_scene->get_state()->get_all_groups();
-}
-
 void EditorFileSystem::update_file(const String &p_file) {
 	ERR_FAIL_COND(p_file.is_empty());
 	update_files({ p_file });

editor/editor_file_system.h

@@ -290,7 +290,6 @@ class EditorFileSystem : public Node {
 	void _queue_update_scene_groups(const String &p_path);
 	void _update_scene_groups();
 	void _update_pending_scene_groups();
-	HashSet<StringName> _get_scene_groups(const String &p_path);
 	void _get_all_scenes(EditorFileSystemDirectory *p_dir, HashSet<String> &r_list);
 
 	String _get_global_script_class(const String &p_type, const String &p_path, String *r_extends, String *r_icon_path) const;

scene/resources/packed_scene.cpp

@@ -2124,6 +2124,56 @@ void PackedScene::recreate_state() {
 #endif
 }
 
+#ifdef TOOLS_ENABLED
+HashSet<StringName> PackedScene::get_scene_groups(const String &p_path) {
+	{
+		Ref<PackedScene> packed_scene = ResourceCache::get_ref(p_path);
+		if (packed_scene.is_valid()) {
+			return packed_scene->get_state()->get_all_groups();
+		}
+	}
+
+	if (p_path.get_extension() == "tscn") {
+		Ref<FileAccess> scene_file = FileAccess::open(p_path, FileAccess::READ);
+		ERR_FAIL_COND_V(scene_file.is_null(), HashSet<StringName>());
+
+		HashSet<StringName> ret;
+		while (!scene_file->eof_reached()) {
+			const String line = scene_file->get_line();
+			if (!line.begins_with("[node")) {
+				continue;
+			}
+
+			int i = line.find("groups=[");
+			if (i == -1) {
+				continue;
+			}
+
+			int j = line.find_char(']', i);
+			while (i < j) {
+				i = line.find_char('"', i);
+				if (i == -1) {
+					break;
+				}
+
+				int k = line.find_char('"', i + 1);
+				if (k == -1) {
+					break;
+				}
+
+				ret.insert(line.substr(i + 1, k - i - 1));
+				i = k + 1;
+			}
+		}
+		return ret;
+	} else {
+		Ref<PackedScene> packed_scene = ResourceLoader::load(p_path);
+		ERR_FAIL_COND_V(packed_scene.is_null(), HashSet<StringName>());
+		return packed_scene->get_state()->get_all_groups();
+	}
+}
+#endif
+
 Ref<SceneState> PackedScene::get_state() const {
 	return state;
 }

scene/resources/packed_scene.h

@@ -270,6 +270,7 @@ class PackedScene : public Resource {
 		state->set_last_modified_time(p_time);
 	}
 
+	static HashSet<StringName> get_scene_groups(const String &p_path);
 #endif
 	Ref<SceneState> get_state() const;