Trait System

core/object/object.cpp

@@ -932,6 +932,7 @@ void Object::set_script(const Variant &p_script) {
 		ERR_FAIL_COND_MSG(s.is_null(), "Cannot set object script. Parameter should be null or a reference to a valid script.");
 		ERR_FAIL_COND_MSG(s->is_abstract(), vformat("Cannot set object script. Script '%s' should not be abstract.", s->get_path()));
 	}
+	ERR_FAIL_COND_MSG(!s->is_attachable(), vformat("Cannot set object script. Script '%s' is not attachable.", s->get_path()));
 
 	script = p_script;
 

core/object/script_language.cpp

@@ -173,6 +173,7 @@ void Script::_bind_methods() {
 
 	ClassDB::bind_method(D_METHOD("is_tool"), &Script::is_tool);
 	ClassDB::bind_method(D_METHOD("is_abstract"), &Script::is_abstract);
+	ClassDB::bind_method(D_METHOD("is_attachable"), &Script::is_attachable);
 
 	ClassDB::bind_method(D_METHOD("get_rpc_config"), &Script::get_rpc_config);
 

core/object/script_language.h

@@ -166,6 +166,7 @@ class Script : public Resource {
 	virtual bool is_tool() const = 0;
 	virtual bool is_valid() const = 0;
 	virtual bool is_abstract() const = 0;
+	virtual bool is_attachable() const { return true; }
 
 	virtual ScriptLanguage *get_language() const = 0;
 
@@ -214,6 +215,7 @@ class ScriptLanguage : public Object {
 	virtual void init() = 0;
 	virtual String get_type() const = 0;
 	virtual String get_extension() const = 0;
+	virtual bool is_language_script_attachable() const { return true; }
 	virtual void finish() = 0;
 
 	/* EDITOR FUNCTIONS */

doc/classes/Script.xml

@@ -6,7 +6,7 @@
 	<description>
 		A class stored as a resource. A script extends the functionality of all objects that instantiate it.
 		This is the base class for all scripts and should not be used directly. Trying to create a new script with this class will result in an error.
-		The [code]new[/code] method of a script subclass creates a new instance. [method Object.set_script] extends an existing object, if that object's class matches one of the script's base classes.
+		The [code]new[/code] method of a script subclass creates a new instance. [method Object.set_script] extends an existing object, if that object's class matches one of the script's base classes and if script is attachable check by [method is_attachable].
 	</description>
 	<tutorials>
 		<link title="Scripting documentation index">$DOCS_URL/tutorials/scripting/index.html</link>
@@ -115,6 +115,12 @@
 				Returns [code]true[/code] if the script is an abstract script. An abstract script does not have a constructor and cannot be instantiated.
 			</description>
 		</method>
+		<method name="is_attachable" qualifiers="const">
+			<return type="bool" />
+			<description>
+				Returns [code]true[/code] if the script is able to be attached to [Object].
+			</description>
+		</method>
 		<method name="is_tool" qualifiers="const">
 			<return type="bool" />
 			<description>

editor/script_create_dialog.cpp

@@ -128,10 +128,16 @@ void ScriptCreateDialog::_notification(int p_what) {
 		} break;
 
 		case NOTIFICATION_THEME_CHANGED: {
+			int skipped_lang = 0;
 			for (int i = 0; i < ScriptServer::get_language_count(); i++) {
-				Ref<Texture2D> language_icon = get_editor_theme_icon(ScriptServer::get_language(i)->get_type());
+				ScriptLanguage *lang = ScriptServer::get_language(i);
+				if (lang->is_language_script_attachable()) {
+					skipped_lang++;
+					continue;
+				}
+				Ref<Texture2D> language_icon = get_editor_theme_icon(lang->get_type());
 				if (language_icon.is_valid()) {
-					language_menu->set_item_icon(i, language_icon);
+					language_menu->set_item_icon(i - skipped_lang, language_icon);
 				}
 			}
 
@@ -855,11 +861,15 @@ ScriptCreateDialog::ScriptCreateDialog() {
 	gc->add_child(language_menu);
 
 	default_language = -1;
+	int add_lang_index = 0;
 	for (int i = 0; i < ScriptServer::get_language_count(); i++) {
-		String lang = ScriptServer::get_language(i)->get_name();
-		language_menu->add_item(lang);
-		if (lang == "GDScript") {
-			default_language = i;
+		ScriptLanguage *lang = ScriptServer::get_language(i);
+		if (lang->is_language_script_attachable()) {
+			language_menu->add_item(lang->get_name());
+			if (lang->get_name() == "GDScript") {
+				default_language = add_lang_index;
+			}
+			add_lang_index++;
 		}
 	}
 	if (default_language >= 0) {

modules/gdscript/.editorconfig

@@ -1,3 +1,7 @@
 [*.gd]
 indent_size = 4
 trim_trailing_whitespace = true
+
+[*.gdt]
+indent_size = 4
+trim_trailing_whitespace = true

modules/gdscript/doc_classes/GDTrait.xml

@@ -0,0 +1,13 @@
+<?xml version="1.0" encoding="UTF-8" ?>
+<class name="GDTrait" inherits="GDScript" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="../../../doc/class.xsd">
+	<brief_description>
+		A script implemented in the GDScript programming language.
+	</brief_description>
+	<description>
+		See [GDScript] or [@GDScript] instead.
+		Helper Script to store Traits for GDScript, its not attachable to objects [method Object.set_script].Saved with the [code].gdt[/code] extension, for GDScript  programming language external Traits.
+	</description>
+	<tutorials>
+		<link title="GDScript documentation index">$DOCS_URL/tutorials/scripting/gdscript/index.html</link>
+	</tutorials>
+</class>

modules/gdscript/editor/gdscript_docgen.cpp

@@ -124,6 +124,7 @@ void GDScriptDocGen::_doctype_from_gdtype(const GDType &p_gdtype, String &r_type
 			}
 			r_type = "Object";
 			return;
+		case GDType::TRAIT:
 		case GDType::CLASS:
 			if (p_gdtype.is_meta_type) {
 				r_type = GDScript::get_class_static();

modules/gdscript/editor/gdscript_highlighter.cpp

@@ -679,6 +679,7 @@ String GDScriptSyntaxHighlighter::_get_name() const {
 PackedStringArray GDScriptSyntaxHighlighter::_get_supported_languages() const {
 	PackedStringArray languages;
 	languages.push_back("GDScript");
+	languages.push_back("GDTrait");
 	return languages;
 }
 

modules/gdscript/editor/gdscript_translation_parser_plugin.cpp

@@ -79,6 +79,7 @@ void GDScriptEditorTranslationParserPlugin::_traverse_class(const GDScriptParser
 		const GDScriptParser::ClassNode::Member &m = p_class->members[i];
 		// Other member types can't contain translatable strings.
 		switch (m.type) {
+			case GDScriptParser::ClassNode::Member::TRAIT:
 			case GDScriptParser::ClassNode::Member::CLASS:
 				_traverse_class(m.m_class);
 				break;

modules/gdscript/gdscript.cpp

@@ -2575,6 +2575,16 @@ void GDScriptLanguage::reload_scripts(const Array &p_scripts, bool p_soft_reload
 	for (Ref<GDScript> &scr : scripts) {
 		bool reload = p_scripts.has(scr) || to_reload.has(scr->get_base());
 
+		// Reload if saved scripts stores trait for script.
+		if (!reload) {
+			for (const Variant &saved_scr : p_scripts) {
+				reload = scr->traits_path.has(static_cast<Ref<GDScript>>(saved_scr)->get_path());
+				if (reload) {
+					break;
+				}
+			}
+		}
+
 		if (!reload) {
 			continue;
 		}
@@ -2741,7 +2751,9 @@ void GDScriptLanguage::get_reserved_words(List<String> *p_words) const {
 		"namespace", // Reserved for potential future use.
 		"signal",
 		"static",
-		"trait", // Reserved for potential future use.
+		"trait",
+		"trait_name",
+		"uses",
 		"var",
 		// Other keywords.
 		"await",
@@ -2797,7 +2809,7 @@ bool GDScriptLanguage::is_control_flow_keyword(const String &p_keyword) const {
 }
 
 bool GDScriptLanguage::handles_global_class_type(const String &p_type) const {
-	return p_type == "GDScript";
+	return p_type == "GDScript" || p_type == "GDTrait";
 }
 
 String GDScriptLanguage::get_global_class_name(const String &p_path, String *r_base_type, String *r_icon_path) const {
@@ -2868,7 +2880,7 @@ String GDScriptLanguage::get_global_class_name(const String &p_path, String *r_b
 						while (extend_classes.size() > 0) {
 							bool found = false;
 							for (int i = 0; i < subclass->members.size(); i++) {
-								if (subclass->members[i].type != GDScriptParser::ClassNode::Member::CLASS) {
+								if (subclass->members[i].type != GDScriptParser::ClassNode::Member::CLASS && subclass->members[i].type != GDScriptParser::ClassNode::Member::TRAIT) {
 									continue;
 								}
 
@@ -2908,8 +2920,12 @@ thread_local GDScriptLanguage::CallStack GDScriptLanguage::_call_stack;
 
 GDScriptLanguage::GDScriptLanguage() {
 	calls = 0;
-	ERR_FAIL_COND(singleton);
-	singleton = this;
+
+	if (singleton == nullptr) {
+		// TODO: Need better solution. Its hack to allow GDTraitLanguage to share same singleton.
+		singleton = this;
+	}
+
 	strings._init = StaticCString::create("_init");
 	strings._static_init = StaticCString::create("_static_init");
 	strings._notification = StaticCString::create("_notification");
@@ -2993,6 +3009,19 @@ Ref<GDScript> GDScriptLanguage::get_script_by_fully_qualified_name(const String
 	return scr;
 }
 
+/* GDTRAIT */
+String GDTraitLanguage::get_name() const {
+	return "GDTrait";
+}
+
+String GDTraitLanguage::get_type() const {
+	return "GDTrait";
+}
+
+String GDTraitLanguage::get_extension() const {
+	return "gdt";
+}
+
 /*************** RESOURCE ***************/
 
 Ref<Resource> ResourceFormatLoaderGDScript::load(const String &p_path, const String &p_original_path, Error *r_error, bool p_use_sub_threads, float *r_progress, CacheMode p_cache_mode) {
@@ -3015,18 +3044,22 @@ Ref<Resource> ResourceFormatLoaderGDScript::load(const String &p_path, const Str
 
 void ResourceFormatLoaderGDScript::get_recognized_extensions(List<String> *p_extensions) const {
 	p_extensions->push_back("gd");
+	p_extensions->push_back("gdt");
 	p_extensions->push_back("gdc");
 }
 
 bool ResourceFormatLoaderGDScript::handles_type(const String &p_type) const {
-	return (p_type == "Script" || p_type == "GDScript");
+	return (p_type == "Script" || p_type == "GDScript" || p_type == "GDTrait");
 }
 
 String ResourceFormatLoaderGDScript::get_resource_type(const String &p_path) const {
 	String el = p_path.get_extension().to_lower();
 	if (el == "gd" || el == "gdc") {
 		return "GDScript";
 	}
+	if (el == "gdt") {
+		return "GDTrait";
+	}
 	return "";
 }
 
@@ -3077,6 +3110,7 @@ Error ResourceFormatSaverGDScript::save(const Ref<Resource> &p_resource, const S
 void ResourceFormatSaverGDScript::get_recognized_extensions(const Ref<Resource> &p_resource, List<String> *p_extensions) const {
 	if (Object::cast_to<GDScript>(*p_resource)) {
 		p_extensions->push_back("gd");
+		p_extensions->push_back("gdt");
 	}
 }
 

modules/gdscript/gdscript.h

@@ -185,6 +185,7 @@ class GDScript : public Script {
 	String fully_qualified_name;
 	String simplified_icon_path;
 	SelfList<GDScript> script_list;
+	Vector<String> traits_path; // File path from used traits for reload.
 
 	SelfList<GDScriptFunctionState>::List pending_func_states;
 
@@ -641,6 +642,22 @@ class GDScriptLanguage : public ScriptLanguage {
 	~GDScriptLanguage();
 };
 
+/* GDTRAIT */
+class GDTrait : public GDScript {
+	GDCLASS(GDTrait, GDScript);
+
+public:
+	virtual bool is_attachable() const override { return false; }
+};
+
+class GDTraitLanguage : public GDScriptLanguage {
+public:
+	virtual String get_name() const override;
+	virtual String get_type() const override;
+	virtual String get_extension() const override;
+	virtual bool is_language_script_attachable() const override { return false; }
+};
+
 class ResourceFormatLoaderGDScript : public ResourceFormatLoader {
 public:
 	virtual Ref<Resource> load(const String &p_path, const String &p_original_path = "", Error *r_error = nullptr, bool p_use_sub_threads = false, float *r_progress = nullptr, CacheMode p_cache_mode = CACHE_MODE_REUSE) override;