Add a const call mode to Object, Variant and Script.

For this to work safely (user not call queue_free or something in the expression), a const call mode was added to Object and Variant (and optionally Script).

This mode ensures only const functions can be called, making it safe to use from the editor.

Co-Authored-By: reduz <reduzio@gmail.com>

4 files changed, 57 insertions, 0 deletions

diff --git a/core/object/object.cpp b/core/object/object.cpp
index 6585c3fa79..440da00c17 100644
--- a/core/object/object.cpp
+++ b/core/object/object.cpp
@@ -669,6 +669,7 @@ Variant Object::callp(const StringName &p_method, const Variant **p_args, int p_
 			case Callable::CallError::CALL_ERROR_INVALID_ARGUMENT:
 			case Callable::CallError::CALL_ERROR_TOO_MANY_ARGUMENTS:
 			case Callable::CallError::CALL_ERROR_TOO_FEW_ARGUMENTS:
+			case Callable::CallError::CALL_ERROR_METHOD_NOT_CONST:
 				return ret;
 			case Callable::CallError::CALL_ERROR_INSTANCE_IS_NULL: {
 			}
@@ -688,6 +689,54 @@ Variant Object::callp(const StringName &p_method, const Variant **p_args, int p_
 	return ret;
 }
 
+Variant Object::call_const(const StringName &p_method, const Variant **p_args, int p_argcount, Callable::CallError &r_error) {
+	r_error.error = Callable::CallError::CALL_OK;
+
+	if (p_method == CoreStringNames::get_singleton()->_free) {
+		// Free is not const, so fail.
+		r_error.error = Callable::CallError::CALL_ERROR_METHOD_NOT_CONST;
+		return Variant();
+	}
+
+	Variant ret;
+	OBJ_DEBUG_LOCK
+
+	if (script_instance) {
+		ret = script_instance->call_const(p_method, p_args, p_argcount, r_error);
+		//force jumptable
+		switch (r_error.error) {
+			case Callable::CallError::CALL_OK:
+				return ret;
+			case Callable::CallError::CALL_ERROR_INVALID_METHOD:
+				break;
+			case Callable::CallError::CALL_ERROR_METHOD_NOT_CONST:
+				break;
+			case Callable::CallError::CALL_ERROR_INVALID_ARGUMENT:
+			case Callable::CallError::CALL_ERROR_TOO_MANY_ARGUMENTS:
+			case Callable::CallError::CALL_ERROR_TOO_FEW_ARGUMENTS:
+				return ret;
+			case Callable::CallError::CALL_ERROR_INSTANCE_IS_NULL: {
+			}
+		}
+	}
+
+	//extension does not need this, because all methods are registered in MethodBind
+
+	MethodBind *method = ClassDB::get_method(get_class_name(), p_method);
+
+	if (method) {
+		if (!method->is_const()) {
+			r_error.error = Callable::CallError::CALL_ERROR_METHOD_NOT_CONST;
+			return ret;
+		}
+		ret = method->call(this, p_args, p_argcount, r_error);
+	} else {
+		r_error.error = Callable::CallError::CALL_ERROR_INVALID_METHOD;
+	}
+
+	return ret;
+}
+
 void Object::notification(int p_notification, bool p_reversed) {
 	_notificationv(p_notification, p_reversed);
 
diff --git a/core/object/object.h b/core/object/object.h
index 7dac96bc2b..e065634000 100644
--- a/core/object/object.h
+++ b/core/object/object.h
@@ -67,6 +67,7 @@ enum PropertyHint {
 	PROPERTY_HINT_GLOBAL_DIR, ///< a directory path must be passed
 	PROPERTY_HINT_RESOURCE_TYPE, ///< a resource object type
 	PROPERTY_HINT_MULTILINE_TEXT, ///< used for string properties that can contain multiple lines
+	PROPERTY_HINT_EXPRESSION, ///< used for string properties that can contain multiple lines
 	PROPERTY_HINT_PLACEHOLDER_TEXT, ///< used to set a placeholder text for string properties
 	PROPERTY_HINT_COLOR_NO_ALPHA, ///< used for ignoring alpha component when editing a color
 	PROPERTY_HINT_IMAGE_COMPRESS_LOSSY,
@@ -759,6 +760,7 @@ public:
 	void get_method_list(List<MethodInfo> *p_list) const;
 	Variant callv(const StringName &p_method, const Array &p_args);
 	virtual Variant callp(const StringName &p_method, const Variant **p_args, int p_argcount, Callable::CallError &r_error);
+	virtual Variant call_const(const StringName &p_method, const Variant **p_args, int p_argcount, Callable::CallError &r_error);
 
 	template <typename... VarArgs>
 	Variant call(const StringName &p_method, VarArgs... p_args) {
diff --git a/core/object/script_language.cpp b/core/object/script_language.cpp
index 66c9a80193..4623d0e525 100644
--- a/core/object/script_language.cpp
+++ b/core/object/script_language.cpp
@@ -295,6 +295,11 @@ void ScriptServer::save_global_classes() {
 }
 
 ////////////////////
+
+Variant ScriptInstance::call_const(const StringName &p_method, const Variant **p_args, int p_argcount, Callable::CallError &r_error) {
+	return callp(p_method, p_args, p_argcount, r_error);
+}
+
 void ScriptInstance::get_property_state(List<Pair<StringName, Variant>> &state) {
 	List<PropertyInfo> pinfo;
 	get_property_list(&pinfo);
diff --git a/core/object/script_language.h b/core/object/script_language.h
index 0a8e79a24e..776a9bfaab 100644
--- a/core/object/script_language.h
+++ b/core/object/script_language.h
@@ -190,6 +190,7 @@ public:
 		return callp(p_method, sizeof...(p_args) == 0 ? nullptr : (const Variant **)argptrs, sizeof...(p_args), cerr);
 	}
 
+	virtual Variant call_const(const StringName &p_method, const Variant **p_args, int p_argcount, Callable::CallError &r_error); // implement if language supports const functions
 	virtual void notification(int p_notification) = 0;
 	virtual String to_string(bool *r_valid) {
 		if (r_valid) {