OrderState.php

<?php
/**
 * Copyright © Magento, Inc. All rights reserved.
 * See COPYING.txt for license details.
 */
declare(strict_types=1);

namespace Magento\SalesGraphQlAux\Model\Resolver;

use Magento\Framework\Exception\LocalizedException;
use Magento\Framework\GraphQl\Config\Element\Field;
use Magento\Framework\GraphQl\Query\ResolverInterface;
use Magento\Framework\GraphQl\Schema\Type\ResolveInfo;
use Magento\Sales\Api\Data\OrderInterface;

/**
 * @inheritdoc
 */
class OrderState implements ResolverInterface
{
    /**
     * @inheritDoc
     */
    public function resolve(
        Field $field,
        $context,
        ResolveInfo $info,
        array $value = null,
        array $args = null
    ) {
        if (!(($value['model'] ?? null) instanceof OrderInterface)) {
            throw new LocalizedException(__('"model" value should be specified, use customer query.'));
        }

        /** @var OrderInterface $order */
        $order = $value['model'];

        return $order->getState();
    }
}