core/AssetManager/UIAssetCacheBuster.php

<?php

/**
 * Matomo - free/libre analytics platform
 *
 * @link    https://matomo.org
 * @license https://www.gnu.org/licenses/gpl-3.0.html GPL v3 or later
 *
 * @method static \Piwik\AssetManager\UIAssetCacheBuster getInstance()
 */

namespace Piwik\AssetManager;

use Piwik\Plugin\Manager;
use Piwik\Singleton;
use Piwik\Version;

class UIAssetCacheBuster extends Singleton
{
    /**
     * Cache buster based on
     *  - Piwik version
     *  - PHP version
     *  - Loaded plugins (name and version)
     *  - Latest git hash of the master branch (if available)
     *
     * @param string[]|false $pluginNames
     * @return string
     */
    public function piwikVersionBasedCacheBuster($pluginNames = false)
    {
        static $cachedCacheBuster = null;

        if (empty($cachedCacheBuster) || $pluginNames !== false) {
            $masterFile     = PIWIK_INCLUDE_PATH . '/.git/refs/heads/master';
            $currentGitHash = file_exists($masterFile) ? @file_get_contents($masterFile) : '';
            $manager = Manager::getInstance();

            $plugins = !$pluginNames ? $manager->getActivatedPlugins() : $pluginNames;
            sort($plugins);

            $pluginsInfo = '';
            foreach ($plugins as $pluginName) {
                if ($manager->isPluginLoaded($pluginName)) {
                    $plugin      = $manager->getLoadedPlugin($pluginName);
                    $pluginsInfo .= $plugin->getPluginName() . $plugin->getVersion() . ',';
                }
            }

            $cacheBuster = md5($pluginsInfo . PHP_VERSION . Version::VERSION . trim($currentGitHash ?: ''));

            if ($pluginNames !== false) {
                return $cacheBuster;
            }

            $cachedCacheBuster = $cacheBuster;
        }

        return $cachedCacheBuster;
    }

    /**
     * @param string $content
     * @return string
     */
    public function md5BasedCacheBuster($content)
    {
        return md5($content);
    }
}