RequestFormatCacheContext.php

<?php

namespace Drupal\Core\Cache\Context;

use Drupal\Core\Cache\CacheableMetadata;

/**
 * Defines the RequestFormatCacheContext service, for "per format" caching.
 *
 * Cache context ID: 'request_format'.
 */
class RequestFormatCacheContext extends RequestStackCacheContextBase {
    
    /**
     * {@inheritdoc}
     */
    public static function getLabel() {
        return t('Request format');
    }
    
    /**
     * {@inheritdoc}
     */
    public function getContext() {
        return $this->requestStack
            ->getCurrentRequest()
            ->getRequestFormat();
    }
    
    /**
     * {@inheritdoc}
     */
    public function getCacheableMetadata() {
        return new CacheableMetadata();
    }

}