AssetGroupSetHashTrait.php

<?php

namespace Drupal\Core\Asset;

use Drupal\Component\Utility\Crypt;
use Drupal\Core\Site\Settings;

/**
 * Provides a method to generate a normalized hash of a given asset group set.
 */
trait AssetGroupSetHashTrait {
    
    /**
     * Generates a hash for an array of asset groups.
     *
     * @param array $group
     *   An asset group.
     *
     * @return string
     *   A hash to uniquely identify the groups.
     */
    protected function generateHash(array $group) : string {
        $normalized = [];
        $group_keys = [
            'type' => NULL,
            'group' => NULL,
            'media' => NULL,
            'browsers' => NULL,
        ];
        $normalized['asset_group'] = array_intersect_key($group, $group_keys);
        $normalized['asset_group']['items'] = [];
        // Remove some keys to make the hash more stable.
        $omit_keys = [
            'weight' => NULL,
        ];
        foreach ($group['items'] as $key => $asset) {
            $normalized['asset_group']['items'][$key] = array_diff_key($asset, $group_keys, $omit_keys);
            // If the version is set to -1, this means there is no version in the
            // library definition. To ensure unique hashes when unversioned files
            // change, replace the version with a hash of the file contents.
            if ($asset['version'] === -1) {
                $normalized['asset_group']['items'][$key]['version'] = hash('xxh64', file_get_contents($asset['data']));
            }
        }
        // The asset array ensures that a valid hash can only be generated via the
        // same code base. Additionally use the hash salt to ensure that hashes are
        // not re-usable between different installations.
        return Crypt::hmacBase64(serialize($normalized), Settings::getHashSalt());
    }

}