magento2/app/code/Magento/CustomerGraphQl/Model/Resolver/Customer.php

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

namespace Magento\CustomerGraphQl\Model\Resolver;

use Magento\CustomerGraphQl\Model\Customer\GetCustomer;
use Magento\Framework\GraphQl\Exception\GraphQlAuthorizationException;
use Magento\Framework\GraphQl\Schema\Type\ResolveInfo;
use Magento\CustomerGraphQl\Model\Customer\ExtractCustomerData;
use Magento\Framework\GraphQl\Config\Element\Field;
use Magento\Framework\GraphQl\Query\ResolverInterface;
use Magento\GraphQl\Model\Query\ContextInterface;

/**
 * Customers field resolver, used for GraphQL request processing.
 */
class Customer implements ResolverInterface
{
    /**
     * @var GetCustomer
     */
    private $getCustomer;

    /**
     * @var ExtractCustomerData
     */
    private $extractCustomerData;

    /**
     * @param GetCustomer $getCustomer
     * @param ExtractCustomerData $extractCustomerData
     */
    public function __construct(
        GetCustomer $getCustomer,
        ExtractCustomerData $extractCustomerData
    ) {
        $this->getCustomer = $getCustomer;
        $this->extractCustomerData = $extractCustomerData;
    }

    /**
     * @inheritdoc
     */
    public function resolve(
        Field $field,
        $context,
        ResolveInfo $info,
        array $value = null,
        array $args = null
    ) {
        /** @var ContextInterface $context */
        if (false === $context->getExtensionAttributes()->getIsCustomer()) {
            throw new GraphQlAuthorizationException(__('The current customer isn\'t authorized.'));
        }

        $customer = $this->getCustomer->execute($context);
        return $this->extractCustomerData->execute($customer);
    }
}