PromotionExpressionValidator.php

<?php

class PromotionExpressionValidator extends ConstraintValidator
{
    private $expressionLanguage;
    private $loadDummyOrder;

    public function __construct(
        ExpressionLanguage $expressionLanguage,
        LoadDummyOrder $loadDummyOrder
    )
    {

        $this->expressionLanguage = $expressionLanguage;
        $this->loadDummyOrder = $loadDummyOrder;
    }

    public function validate($value, Constraint $constraint)
    {
        try {
            $this->expressionLanguage->parse(
                $value['expression'],
                [$value['itemBased'] ? 'item' : 'order']
            );
        } catch (SyntaxError $e) {
            return $this->context->addViolationAt(
                'expression',
                $e->getMessage()
            );
        }

        if ($value['itemBased']) {
            $process = $this->runOnDummyOrderItem($value['expression']);
        } else {
            $process = $this->runOnDummyOrder($value['expression']);
        }
        if (0 !== $process->getExitCode() || null !== $process->getOutput()) {
            return $this->context->addViolationAt(
                'expression',
                null === $process->getOutput() ? $constraint->message : trim($process->getOutput())
            );
        }
    }

    private function runOnDummyOrder($expression)
    {
        return $this->runOnObject(
            'order',
            $this->loadDummyOrder->load(),
            $expression
        );
    }

    private function runOnDummyOrderItem($expression)
    {
        return $this->runOnObject(
            'item',
            $this->loadDummyOrder->load()->getItems()->first(),
            $expression
        );
    }

    private function runOnObject($key, $value, $expression)
    {
        $process = new PhpProcess(sprintf("<?php
                require __DIR__.'/../vendor/autoload.php';

                ini_set('display_errors', 1);

                (new %s())->evaluate(
                    \"%s\",
                    ['%s' => unserialize('%s')]
                );
            ",
            get_class($this->expressionLanguage),
            $expression,
            $key,
            serialize($value)
        ));

        $process->run();

        return $process;
    }
}