class InstallerServiceProvider

class InstallerServiceProvider extends NormalInstallerServiceProvider implements ServiceProviderInterface, ServiceModifierInterface {
    
    /**
     * {@inheritdoc}
     */
    public function register(ContainerBuilder $container) {
        // Inject the special configuration storage for the installer.
        // This special implementation MUST NOT be used anywhere else than the early
        // installer environment.
        $container->register('config.storage', 'Drupal\\Core\\Config\\InstallStorage');
        // Replace services with in-memory implementations.
        $container->register('keyvalue', 'Drupal\\Core\\KeyValueStore\\KeyValueMemoryFactory');
        $container->register('keyvalue.expirable', 'Drupal\\Core\\KeyValueStore\\KeyValueNullExpirableFactory');
        // Replace services with no-op implementations.
        $container->register('url_generator', 'Drupal\\Core\\Routing\\NullGenerator')
            ->addArgument(new Reference('request_stack'));
        $container->register('path_processor_manager', 'Drupal\\Core\\PathProcessor\\NullPathProcessorManager');
        $container->register('router.dumper', 'Drupal\\Core\\Routing\\NullMatcherDumper');
        // Replace the route builder with an empty implementation.
        // @todo Convert installer steps into routes; add an installer.routing.yml.
        $definition = $container->getDefinition('router.builder');
        $definition->setClass('Drupal\\Core\\Installer\\InstallerRouteBuilder')
            ->setLazy(FALSE);
        parent::register($container);
    }
    
    /**
     * {@inheritdoc}
     */
    public function alter(ContainerBuilder $container) {
        // Disable Twig cache (php storage does not exist yet).
        $twig_config = $container->getParameter('twig.config');
        $twig_config['cache'] = FALSE;
        $container->setParameter('twig.config', $twig_config);
        // No service may persist when the early installer kernel is rebooted into
        // the production environment.
        // @todo The DrupalKernel reboot performed by drupal_install_system() is
        //   actually not a "regular" reboot (like ModuleInstaller::install()), so
        //   services are not actually persisted.
        foreach ($container->findTaggedServiceIds('persist') as $id => $tags) {
            $definition = $container->getDefinition($id);
            $definition->clearTag('persist');
        }
    }

}