PathParentCacheContext.php

<?php

namespace Drupal\Core\Cache\Context;

use Drupal\Core\Cache\CacheableMetadata;

/**
 * Defines a cache context service for path parents.
 *
 * Cache context ID: 'url.path.parent'.
 *
 * This allows for caching based on the path, excluding everything after the
 * last forward slash.
 */
class PathParentCacheContext extends RequestStackCacheContextBase implements CacheContextInterface {
    
    /**
     * {@inheritdoc}
     */
    public static function getLabel() {
        return t('Parent path');
    }
    
    /**
     * {@inheritdoc}
     */
    public function getContext() {
        $request = $this->requestStack
            ->getCurrentRequest();
        $path_elements = explode('/', trim($request->getPathInfo(), '/'));
        array_pop($path_elements);
        return implode('/', $path_elements);
    }
    
    /**
     * {@inheritdoc}
     */
    public function getCacheableMetadata() {
        return new CacheableMetadata();
    }

}