Added support for generic type properties in gdscript

This change allows scripts to use untyped properties.
Their type can be changed in the inspector the same way as for
elements in Array or Dictionary.

This implementation uses properties of type TYPE_NIL with the
existing usage flag PROPERTY_USAGE_NIL_IS_VARIANT.

Syntax for property list:

{
	"name": "generic_var",
	"type": TYPE_NIL,
	"usage": PROPERTY_USAGE_DEFAULT | PROPERTY_USAGE_NIL_IS_VARIANT,
	"hint": PROPERTY_HINT_NONE,
	"hint_string" : "",
}

Syntax for exported variable:
export(Variant) var generic_export_var

core/global_constants.cpp

@@ -552,6 +552,7 @@ void register_global_constants() {
 	BIND_GLOBAL_ENUM_CONSTANT(PROPERTY_USAGE_NO_INSTANCE_STATE);
 	BIND_GLOBAL_ENUM_CONSTANT(PROPERTY_USAGE_RESTART_IF_CHANGED);
 	BIND_GLOBAL_ENUM_CONSTANT(PROPERTY_USAGE_SCRIPT_VARIABLE);
+	BIND_GLOBAL_ENUM_CONSTANT(PROPERTY_USAGE_NIL_IS_VARIANT);
 
 	BIND_GLOBAL_ENUM_CONSTANT(PROPERTY_USAGE_DEFAULT);
 	BIND_GLOBAL_ENUM_CONSTANT(PROPERTY_USAGE_DEFAULT_INTL);

core/script_language.cpp

@@ -469,7 +469,7 @@ void PlaceHolderScriptInstance::update(const List<PropertyInfo> &p_properties, c
 		StringName n = E->get().name;
 		new_values.insert(n);
 
-		if (!values.has(n) || values[n].get_type() != E->get().type) {
+		if (!values.has(n) || (values[n].get_type() != E->get().type && !(E->get().usage & PROPERTY_USAGE_NIL_IS_VARIANT))) {
 			if (p_values.has(n)) {
 				values[n] = p_values[n];
 			}

doc/classes/@GlobalScope.xml

@@ -1411,6 +1411,9 @@
 		<constant name="PROPERTY_USAGE_SCRIPT_VARIABLE" value="8192" enum="PropertyUsageFlags">
 			The property is a script variable which should be serialized and saved in the scene file.
 		</constant>
+		<constant name="PROPERTY_USAGE_NIL_IS_VARIANT" value="524288" enum="PropertyUsageFlags">
+			The property stores a variable of type [Variant]. Used with type flag [code]TYPE_NIL[/code].
+		</constant>
 		<constant name="PROPERTY_USAGE_DEFAULT" value="7" enum="PropertyUsageFlags">
 			Default usage (storage, editor and network).
 		</constant>

editor/editor_properties.cpp

@@ -30,6 +30,7 @@
 
 #include "editor_properties.h"
 
+#include "core/io/marshalls.h"
 #include "editor/editor_resource_preview.h"
 #include "editor/filesystem_dock.h"
 #include "editor_node.h"
@@ -48,6 +49,101 @@ EditorPropertyNil::EditorPropertyNil() {
 	add_child(label);
 }
 
+///////////////////// GENERIC /////////////////////////
+
+void EditorPropertyGeneric::update_property() {
+	Object *object = get_edited_object();
+	StringName edited_prop = get_edited_property();
+	Variant value = object->get(edited_prop);
+	Variant::Type value_type = value.get_type();
+
+	// remove previous controls
+	while (hbox->get_child_count() > 0) {
+		Node *child = hbox->get_child(0);
+		child->queue_delete();
+		hbox->remove_child(child);
+	}
+
+	EditorProperty *prop = nullptr;
+	if (value_type == Variant::NIL) {
+		prop = memnew(EditorPropertyNil);
+	} else if (value_type == Variant::OBJECT && Object::cast_to<EncodedObjectAsID>(value)) {
+		EditorPropertyObjectID *editor = memnew(EditorPropertyObjectID);
+		editor->setup("Object");
+		prop = editor;
+	} else {
+		prop = EditorInspector::instantiate_property_editor(nullptr, value_type, "", PROPERTY_HINT_NONE, "", 0);
+	}
+
+	prop->set_object_and_property(object, edited_prop);
+	prop->set_name_split_ratio(0.0);
+	prop->set_selectable(false);
+	prop->connect("property_changed", callable_mp(this, &EditorPropertyGeneric::_property_changed));
+	prop->connect("object_id_selected", callable_mp(this, &EditorPropertyGeneric::_object_id_selected));
+	prop->set_h_size_flags(SIZE_EXPAND_FILL);
+
+	hbox->add_child(prop);
+
+	Button *edit_button = memnew(Button);
+	edit_button->set_icon(get_theme_icon("Edit", "EditorIcons"));
+	edit_button->connect("pressed", callable_mp(this, &EditorPropertyGeneric::_change_type), varray(edit_button));
+	hbox->add_child(edit_button);
+
+	prop->update_property();
+}
+
+void EditorPropertyGeneric::_property_changed(const String &p_prop, Variant p_value, const String &p_name, bool changing) {
+	emit_changed(get_edited_property(), p_value, p_name, changing);
+}
+
+void EditorPropertyGeneric::_object_id_selected(const String &p_property, ObjectID p_id) {
+	emit_signal("object_id_selected", p_property, p_id);
+}
+
+void EditorPropertyGeneric::_change_type(Object *p_button) {
+	Button *button = Object::cast_to<Button>(p_button);
+	Rect2 rect = button->get_global_rect();
+	change_type->set_as_minsize();
+	change_type->set_position(rect.position + rect.size - Vector2(change_type->get_contents_minimum_size().x, 0));
+	change_type->popup();
+}
+
+void EditorPropertyGeneric::_change_type_menu(int p_index) {
+	Object *object = get_edited_object();
+	StringName edited_prop = get_edited_property();
+	Variant value = object->get(edited_prop);
+	Variant::Type value_type = value.get_type();
+
+	Variant::Type new_value_type = Variant::Type(p_index);
+	if (new_value_type == value_type) {
+		return;
+	}
+
+	Callable::CallError ce;
+	Variant new_value = Variant::construct(new_value_type, nullptr, 0, ce);
+
+	emit_changed(edited_prop, new_value, "", true);
+	update_property();
+}
+
+EditorPropertyGeneric::EditorPropertyGeneric() {
+	hbox = memnew(HBoxContainer);
+	hbox->set_h_size_flags(SIZE_EXPAND_FILL);
+	add_child(hbox);
+
+	change_type = memnew(PopupMenu);
+	add_child(change_type);
+	change_type->connect("id_pressed", callable_mp(this, &EditorPropertyGeneric::_change_type_menu));
+
+	for (int i = 0; i < Variant::VARIANT_MAX; i++) {
+		String type = Variant::get_type_name(Variant::Type(i));
+		change_type->add_item(type, i);
+	}
+}
+
+void EditorPropertyGeneric::_bind_methods() {
+}
+
 ///////////////////// TEXT /////////////////////////
 
 void EditorPropertyText::_text_entered(const String &p_string) {
@@ -3121,8 +3217,13 @@ bool EditorInspectorDefaultPlugin::parse_property(Object *p_object, Variant::Typ
 	switch (p_type) {
 		// atomic types
 		case Variant::NIL: {
-			EditorPropertyNil *editor = memnew(EditorPropertyNil);
-			add_property_editor(p_path, editor);
+			if (p_usage & PROPERTY_USAGE_NIL_IS_VARIANT) {
+				EditorPropertyGeneric *editor = memnew(EditorPropertyGeneric);
+				add_property_editor(p_path, editor);
+			} else {
+				EditorPropertyNil *editor = memnew(EditorPropertyNil);
+				add_property_editor(p_path, editor);
+			}
 		} break;
 		case Variant::BOOL: {
 			EditorPropertyCheck *editor = memnew(EditorPropertyCheck);

editor/editor_properties.h

@@ -41,13 +41,30 @@
 
 class EditorPropertyNil : public EditorProperty {
 	GDCLASS(EditorPropertyNil, EditorProperty);
-	LineEdit *text;
 
 public:
 	virtual void update_property();
 	EditorPropertyNil();
 };
 
+class EditorPropertyGeneric : public EditorProperty {
+	GDCLASS(EditorPropertyGeneric, EditorProperty);
+	HBoxContainer *hbox;
+	PopupMenu *change_type;
+
+	void _property_changed(const String &p_prop, Variant p_value, const String &p_name = String(), bool changing = false);
+	void _object_id_selected(const String &p_property, ObjectID p_id);
+	void _change_type(Object *p_button);
+	void _change_type_menu(int p_index);
+
+protected:
+	static void _bind_methods();
+
+public:
+	virtual void update_property();
+	EditorPropertyGeneric();
+};
+
 class EditorPropertyText : public EditorProperty {
 	GDCLASS(EditorPropertyText, EditorProperty);
 	LineEdit *text;

modules/gdscript/gdscript.cpp

@@ -434,7 +434,9 @@ bool GDScript::_update_exports(bool *r_err, bool p_recursive_call) {
 
 			for (int i = 0; i < c->variables.size(); i++) {
 				if (c->variables[i]._export.type == Variant::NIL) {
-					continue;
+					if (!(c->variables[i]._export.usage & PROPERTY_USAGE_NIL_IS_VARIANT)) {
+						continue;
+					}
 				}
 
 				members_cache.push_back(c->variables[i]._export);

modules/gdscript/gdscript_compiler.cpp

@@ -1942,7 +1942,7 @@ Error GDScriptCompiler::_parse_class_level(GDScript *p_script, const GDScriptPar
 		prop_info.name = name;
 		PropertyInfo export_info = p_class->variables[i]._export;
 
-		if (export_info.type != Variant::NIL) {
+		if (export_info.type != Variant::NIL || export_info.usage & PROPERTY_USAGE_NIL_IS_VARIANT) {
 			if (!minfo.data_type.has_type) {
 				prop_info.type = export_info.type;
 				prop_info.class_name = export_info.class_name;

modules/gdscript/gdscript_parser.cpp

@@ -4604,7 +4604,11 @@ void GDScriptParser::_parse_class(ClassNode *p_class) {
 								} break;
 							}
 						}
-
+					} else if (tokenizer->get_token() == GDScriptTokenizer::TK_IDENTIFIER && tokenizer->get_token_identifier() == "Variant") {
+						current_export.type = Variant::Type::NIL;
+						current_export.usage |= PROPERTY_USAGE_SCRIPT_VARIABLE;
+						current_export.usage |= PROPERTY_USAGE_NIL_IS_VARIANT;
+						tokenizer->advance();
 					} else {
 						parenthesis++;
 						Node *subexpr = _parse_and_reduce_expression(p_class, true, true);
@@ -4832,7 +4836,7 @@ void GDScriptParser::_parse_class(ClassNode *p_class) {
 				ClassNode::Member member;
 
 				bool autoexport = tokenizer->get_token(-1) == GDScriptTokenizer::TK_PR_EXPORT;
-				if (current_export.type != Variant::NIL) {
+				if (current_export.type != Variant::NIL || current_export.usage & PROPERTY_USAGE_NIL_IS_VARIANT) {
 					member._export = current_export;
 					current_export = PropertyInfo();
 				}