getModuleFileNames example

      // database settings are available. None of this is required when the       // installer is running because the installer has its own kernel and       // manages the addition of its own service providers.       // @see install_begin_request()       if ($extensions === FALSE && !InstallerKernel::installationAttempted()) {
        $this->allowDumping = FALSE;
        $this->containerNeedsDumping = FALSE;
        $GLOBALS['conf']['container_service_providers']['InstallerServiceProvider'] = 'Drupal\Core\Installer\InstallerServiceProvider';
      }
      $this->moduleList = $extensions['module'] ?? [];
    }
    $module_filenames = $this->getModuleFileNames();
    $this->classLoaderAddMultiplePsr4($this->getModuleNamespacesPsr4($module_filenames));

    // Load each module's serviceProvider class.     foreach ($module_filenames as $module => $filename) {
      $camelized = ContainerBuilder::camelize($module);
      $name = "{$camelized}ServiceProvider";
      $class = "Drupal\\{$module}\\{$name}";
      if (class_exists($class)) {
        $this->serviceProviderClasses['app'][$module] = $class;
      }
      $filename = dirname($filename) . "/$module.services.yml";