GraphQL\Validator\Rules\NoUndefinedVariables::__invoke PHP Метод

    public function __invoke(ValidationContext $context)
    {
        $variableNameDefined = [];
        return [NodeKind::OPERATION_DEFINITION => ['enter' => function () use(&$variableNameDefined) {
            $variableNameDefined = [];
        }, 'leave' => function (OperationDefinitionNode $operation) use(&$variableNameDefined, $context) {
            $usages = $context->getRecursiveVariableUsages($operation);
            foreach ($usages as $usage) {
                $node = $usage['node'];
                $varName = $node->name->value;
                if (empty($variableNameDefined[$varName])) {
                    $context->reportError(new Error(self::undefinedVarMessage($varName, $operation->name ? $operation->name->value : null), [$node, $operation]));
                }
            }
        }], NodeKind::VARIABLE_DEFINITION => function (VariableDefinitionNode $def) use(&$variableNameDefined) {
            $variableNameDefined[$def->variable->name->value] = true;
        }];
    }