comparison core/includes/install.core.inc @ 0:c75dbcec494b

Initial commit from drush-created site

+<?php
+
+/**
+ * @file
+ * API functions for installing Drupal.
+ */
+
+use Drupal\Component\Utility\UrlHelper;
+use Drupal\Core\DrupalKernel;
+use Drupal\Core\Database\Database;
+use Drupal\Core\Database\DatabaseExceptionWrapper;
+use Drupal\Core\Form\FormState;
+use Drupal\Core\Installer\Exception\AlreadyInstalledException;
+use Drupal\Core\Installer\Exception\InstallerException;
+use Drupal\Core\Installer\Exception\InstallProfileMismatchException;
+use Drupal\Core\Installer\Exception\NoProfilesException;
+use Drupal\Core\Installer\InstallerKernel;
+use Drupal\Core\Language\Language;
+use Drupal\Core\Language\LanguageManager;
+use Drupal\Core\Logger\LoggerChannelFactory;
+use Drupal\Core\Site\Settings;
+use Drupal\Core\StringTranslation\Translator\FileTranslation;
+use Drupal\Core\StackMiddleware\ReverseProxyMiddleware;
+use Drupal\Core\StreamWrapper\PublicStream;
+use Drupal\Core\Extension\ExtensionDiscovery;
+use Drupal\Core\DependencyInjection\ContainerBuilder;
+use Drupal\Core\Url;
+use Drupal\language\Entity\ConfigurableLanguage;
+use Symfony\Cmf\Component\Routing\RouteObjectInterface;
+use Symfony\Component\DependencyInjection\Reference;
+use Symfony\Component\HttpFoundation\Request;
+use Symfony\Component\HttpFoundation\Response;
+use Symfony\Component\Routing\Route;
+use Drupal\user\Entity\User;
+use GuzzleHttp\Exception\RequestException;
+
+/**
+ * Do not run the task during the current installation request.
+ *
+ * This can be used to skip running an installation task when certain
+ * conditions are met, even though the task may still show on the list of
+ * installation tasks presented to the user. For example, the Drupal installer
+ * uses this flag to skip over the database configuration form when valid
+ * database connection information is already available from settings.php. It
+ * also uses this flag to skip language import tasks when the installation is
+ * being performed in English.
+ */
+const INSTALL_TASK_SKIP = 1;
+
+/**
+ * Run the task on each installation request that reaches it.
+ *
+ * This is primarily used by the Drupal installer for bootstrap-related tasks.
+ */
+const INSTALL_TASK_RUN_IF_REACHED = 2;
+
+/**
+ * Run the task on each installation request until the database is set up.
+ *
+ * This is the default method for running tasks and should be used for most
+ * tasks that occur after the database is set up; these tasks will then run
+ * once and be marked complete once they are successfully finished. For
+ * example, the Drupal installer uses this flag for the batch installation of
+ * modules on the new site, and also for the configuration form that collects
+ * basic site information and sets up the site maintenance account.
+ */
+const INSTALL_TASK_RUN_IF_NOT_COMPLETED = 3;
+
+/**
+ * Installs Drupal either interactively or via an array of passed-in settings.
+ *
+ * The Drupal installation happens in a series of steps, which may be spread
+ * out over multiple page requests. Each request begins by trying to determine
+ * the last completed installation step (also known as a "task"), if one is
+ * available from a previous request. Control is then passed to the task
+ * handler, which processes the remaining tasks that need to be run until (a)
+ * an error is thrown, (b) a new page needs to be displayed, or (c) the
+ * installation finishes (whichever happens first).
+ *
+ * @param $class_loader
+ *   The class loader. Normally Composer's ClassLoader, as included by the
+ *   front controller, but may also be decorated; e.g.,
+ *   \Symfony\Component\ClassLoader\ApcClassLoader.
+ * @param $settings
+ *   An optional array of installation settings. Leave this empty for a normal,
+ *   interactive, browser-based installation intended to occur over multiple
+ *   page requests. Alternatively, if an array of settings is passed in, the
+ *   installer will attempt to use it to perform the installation in a single
+ *   page request (optimized for the command line) and not send any output
+ *   intended for the web browser. See install_state_defaults() for a list of
+ *   elements that are allowed to appear in this array.
+ *
+ * @see install_state_defaults()
+ */
+function install_drupal($class_loader, $settings = []) {
+  // Support the old way of calling this function with just a settings array.
+  // @todo Remove this when Drush is updated in the Drupal testing
+  //   infrastructure in https://www.drupal.org/node/2389243
+  if (is_array($class_loader) && $settings === []) {
+    $settings = $class_loader;
+    $class_loader = require __DIR__ . '/../../autoload.php';
+  }
+
+  global $install_state;
+  // Initialize the installation state with the settings that were passed in,
+  // as well as a boolean indicating whether or not this is an interactive
+  // installation.
+  $interactive = empty($settings);
+  $install_state = $settings + ['interactive' => $interactive] + install_state_defaults();
+
+  try {
+    // Begin the page request. This adds information about the current state of
+    // the Drupal installation to the passed-in array.
+    install_begin_request($class_loader, $install_state);
+    // Based on the installation state, run the remaining tasks for this page
+    // request, and collect any output.
+    $output = install_run_tasks($install_state);
+  }
+  catch (InstallerException $e) {
+    // In the non-interactive installer, exceptions are always thrown directly.
+    if (!$install_state['interactive']) {
+      throw $e;
+    }
+    $output = [
+      '#title' => $e->getTitle(),
+      '#markup' => $e->getMessage(),
+    ];
+  }
+
+  // After execution, all tasks might be complete, in which case
+  // $install_state['installation_finished'] is TRUE. In case the last task
+  // has been processed, remove the global $install_state, so other code can
+  // reliably check whether it is running during the installer.
+  // @see drupal_installation_attempted()
+  $state = $install_state;
+  if (!empty($install_state['installation_finished'])) {
+    unset($GLOBALS['install_state']);
+  }
+
+  // All available tasks for this page request are now complete. Interactive
+  // installations can send output to the browser or redirect the user to the
+  // next page.
+  if ($state['interactive']) {
+    // If a session has been initiated in this request, make sure to save it.
+    if ($session = \Drupal::request()->getSession()) {
+      $session->save();
+    }
+    if ($state['parameters_changed']) {
+      // Redirect to the correct page if the URL parameters have changed.
+      install_goto(install_redirect_url($state));
+    }
+    elseif (isset($output)) {
+      // Display a page only if some output is available. Otherwise it is
+      // possible that we are printing a JSON page and theme output should
+      // not be shown.
+      install_display_output($output, $state);
+    }
+    elseif ($state['installation_finished']) {
+      // Redirect to the newly installed site.
+      install_goto('');
+    }
+  }
+}
+
+/**
+ * Returns an array of default settings for the global installation state.
+ *
+ * The installation state is initialized with these settings at the beginning
+ * of each page request. They may evolve during the page request, but they are
+ * initialized again once the next request begins.
+ *
+ * Non-interactive Drupal installations can override some of these default
+ * settings by passing in an array to the installation script, most notably
+ * 'parameters' (which contains one-time parameters such as 'profile' and
+ * 'langcode' that are normally passed in via the URL) and 'forms' (which can
+ * be used to programmatically submit forms during the installation; the keys
+ * of each element indicate the name of the installation task that the form
+ * submission is for, and the values are used as the $form_state->getValues()
+ * array that is passed on to the form submission via
+ * \Drupal::formBuilder()->submitForm()).
+ *
+ * @see \Drupal\Core\Form\FormBuilderInterface::submitForm()
+ */
+function install_state_defaults() {
+  $defaults = [
+    // The current task being processed.
+    'active_task' => NULL,
+    // The last task that was completed during the previous installation
+    // request.
+    'completed_task' => NULL,
+    // TRUE when there are valid config directories.
+    'config_verified' => FALSE,
+    // TRUE when there is a valid database connection.
+    'database_verified' => FALSE,
+    // TRUE if database is empty & ready to install.
+    'database_ready' => FALSE,
+    // TRUE when a valid settings.php exists (containing both database
+    // connection information and config directory names).
+    'settings_verified' => FALSE,
+    // TRUE when the base system has been installed and is ready to operate.
+    'base_system_verified' => FALSE,
+    // Whether a translation file for the selected language will be downloaded
+    // from the translation server.
+    'download_translation' => FALSE,
+    // An array of forms to be programmatically submitted during the
+    // installation. The keys of each element indicate the name of the
+    // installation task that the form submission is for, and the values are
+    // used as the $form_state->getValues() array that is passed on to the form
+    // submission via \Drupal::formBuilder()->submitForm().
+    'forms' => [],
+    // This becomes TRUE only at the end of the installation process, after
+    // all available tasks have been completed and Drupal is fully installed.
+    // It is used by the installer to store correct information in the database
+    // about the completed installation, as well as to inform theme functions
+    // that all tasks are finished (so that the task list can be displayed
+    // correctly).
+    'installation_finished' => FALSE,
+    // Whether or not this installation is interactive. By default this will
+    // be set to FALSE if settings are passed in to install_drupal().
+    'interactive' => TRUE,
+    // An array of parameters for the installation, pre-populated by the URL
+    // or by the settings passed in to install_drupal(). This is primarily
+    // used to store 'profile' (the name of the chosen installation profile)
+    // and 'langcode' (the code of the chosen installation language), since
+    // these settings need to persist from page request to page request before
+    // the database is available for storage.
+    'parameters' => [],
+    // Whether or not the parameters have changed during the current page
+    // request. For interactive installations, this will trigger a page
+    // redirect.
+    'parameters_changed' => FALSE,
+    // An array of information about the chosen installation profile. This will
+    // be filled in based on the profile's .info.yml file.
+    'profile_info' => [],
+    // An array of available installation profiles.
+    'profiles' => [],
+    // The name of the theme to use during installation.
+    'theme' => 'seven',
+    // The server URL where the interface translation files can be downloaded.
+    // Tokens in the pattern will be replaced by appropriate values for the
+    // required translation file.
+    'server_pattern' => 'http://ftp.drupal.org/files/translations/%core/%project/%project-%version.%language.po',
+    // Installation tasks can set this to TRUE to force the page request to
+    // end (even if there is no themable output), in the case of an interactive
+    // installation. This is needed only rarely; for example, it would be used
+    // by an installation task that prints JSON output rather than returning a
+    // themed page. The most common example of this is during batch processing,
+    // but the Drupal installer automatically takes care of setting this
+    // parameter properly in that case, so that individual installation tasks
+    // which implement the batch API do not need to set it themselves.
+    'stop_page_request' => FALSE,
+    // Installation tasks can set this to TRUE to indicate that the task should
+    // be run again, even if it normally wouldn't be. This can be used, for
+    // example, if a single task needs to be spread out over multiple page
+    // requests, or if it needs to perform some validation before allowing
+    // itself to be marked complete. The most common examples of this are batch
+    // processing and form submissions, but the Drupal installer automatically
+    // takes care of setting this parameter properly in those cases, so that
+    // individual installation tasks which implement the batch API or form API
+    // do not need to set it themselves.
+    'task_not_complete' => FALSE,
+    // A list of installation tasks which have already been performed during
+    // the current page request.
+    'tasks_performed' => [],
+    // An array of translation files URIs available for the installation. Keyed
+    // by the translation language code.
+    'translations' => [],
+  ];
+  return $defaults;
+}
+
+/**
+ * Begins an installation request, modifying the installation state as needed.
+ *
+ * This function performs commands that must run at the beginning of every page
+ * request. It throws an exception if the installation should not proceed.
+ *
+ * @param $class_loader
+ *   The class loader. Normally Composer's ClassLoader, as included by the
+ *   front controller, but may also be decorated; e.g.,
+ *   \Symfony\Component\ClassLoader\ApcClassLoader.
+ * @param $install_state
+ *   An array of information about the current installation state. This is
+ *   modified with information gleaned from the beginning of the page request.
+ */
+function install_begin_request($class_loader, &$install_state) {
+  $request = Request::createFromGlobals();
+
+  // Add any installation parameters passed in via the URL.
+  if ($install_state['interactive']) {
+    $install_state['parameters'] += $request->query->all();
+  }
+
+  // Validate certain core settings that are used throughout the installation.
+  if (!empty($install_state['parameters']['profile'])) {
+    $install_state['parameters']['profile'] = preg_replace('/[^a-zA-Z_0-9]/', '', $install_state['parameters']['profile']);
+  }
+  if (!empty($install_state['parameters']['langcode'])) {
+    $install_state['parameters']['langcode'] = preg_replace('/[^a-zA-Z_0-9\-]/', '', $install_state['parameters']['langcode']);
+  }
+
+  // Allow command line scripts to override server variables used by Drupal.
+  require_once __DIR__ . '/bootstrap.inc';
+
+  // Before having installed the system module and being able to do a module
+  // rebuild, prime the drupal_get_filename() static cache with the module's
+  // exact location.
+  // @todo Remove as part of https://www.drupal.org/node/2186491
+  drupal_get_filename('module', 'system', 'core/modules/system/system.info.yml');
+
+  // If the hash salt leaks, it becomes possible to forge a valid testing user
+  // agent, install a new copy of Drupal, and take over the original site.
+  // The user agent header is used to pass a database prefix in the request when
+  // running tests. However, for security reasons, it is imperative that no
+  // installation be permitted using such a prefix.
+  $user_agent = $request->cookies->get('SIMPLETEST_USER_AGENT') ?: $request->server->get('HTTP_USER_AGENT');
+  if ($install_state['interactive'] && strpos($user_agent, 'simpletest') !== FALSE && !drupal_valid_test_ua()) {
+    header($request->server->get('SERVER_PROTOCOL') . ' 403 Forbidden');
+    exit;
+  }
+  if ($install_state['interactive'] && drupal_valid_test_ua()) {
+    // Set the default timezone. While this doesn't cause any tests to fail, PHP
+    // complains if 'date.timezone' is not set in php.ini. The Australia/Sydney
+    // timezone is chosen so all tests are run using an edge case scenario
+    // (UTC+10  and DST). This choice is made to prevent timezone related
+    // regressions and reduce the fragility of the testing system in general.
+    date_default_timezone_set('Australia/Sydney');
+  }
+
+  $site_path = DrupalKernel::findSitePath($request, FALSE);
+  Settings::initialize(dirname(dirname(__DIR__)), $site_path, $class_loader);
+
+  // Ensure that procedural dependencies are loaded as early as possible,
+  // since the error/exception handlers depend on them.
+  require_once __DIR__ . '/../modules/system/system.install';
+  require_once __DIR__ . '/common.inc';
+  require_once __DIR__ . '/file.inc';
+  require_once __DIR__ . '/install.inc';
+  require_once __DIR__ . '/schema.inc';
+  require_once __DIR__ . '/database.inc';
+  require_once __DIR__ . '/form.inc';
+  require_once __DIR__ . '/batch.inc';
+
+  // Load module basics (needed for hook invokes).
+  include_once __DIR__ . '/module.inc';
+  require_once __DIR__ . '/entity.inc';
+
+  // Create a minimal mocked container to support calls to t() in the pre-kernel
+  // base system verification code paths below. The strings are not actually
+  // used or output for these calls.
+  // @todo Separate API level checks from UI-facing error messages.
+  $container = new ContainerBuilder();
+  $container->setParameter('language.default_values', Language::$defaultValues);
+  $container
+    ->register('language.default', 'Drupal\Core\Language\LanguageDefault')
+    ->addArgument('%language.default_values%');
+  $container
+    ->register('string_translation', 'Drupal\Core\StringTranslation\TranslationManager')
+    ->addArgument(new Reference('language.default'));
+
+  // Register the stream wrapper manager.
+  $container
+    ->register('stream_wrapper_manager', 'Drupal\Core\StreamWrapper\StreamWrapperManager')
+    ->addMethodCall('setContainer', [new Reference('service_container')]);
+  $container
+    ->register('file_system', 'Drupal\Core\File\FileSystem')
+    ->addArgument(new Reference('stream_wrapper_manager'))
+    ->addArgument(Settings::getInstance())
+    ->addArgument((new LoggerChannelFactory())->get('file'));
+
+  \Drupal::setContainer($container);
+
+  // Determine whether base system services are ready to operate.
+  try {
+    $sync_directory = config_get_config_directory(CONFIG_SYNC_DIRECTORY);
+    $install_state['config_verified'] = file_exists($sync_directory);
+  }
+  catch (Exception $e) {
+    $install_state['config_verified'] = FALSE;
+  }
+  $install_state['database_verified'] = install_verify_database_settings($site_path);
+  // A valid settings.php has database settings and a hash_salt value. Other
+  // settings like config_directories will be checked by system_requirements().
+  $install_state['settings_verified'] = $install_state['database_verified'] && (bool) Settings::get('hash_salt', FALSE);
+
+  // Install factory tables only after checking the database.
+  if ($install_state['database_verified'] && $install_state['database_ready']) {
+    $container
+      ->register('path.matcher', 'Drupal\Core\Path\PathMatcher')
+      ->addArgument(new Reference('config.factory'));
+  }
+
+  if ($install_state['settings_verified']) {
+    try {
+      $system_schema = system_schema();
+      end($system_schema);
+      $table = key($system_schema);
+      $install_state['base_system_verified'] = Database::getConnection()->schema()->tableExists($table);
+    }
+    catch (DatabaseExceptionWrapper $e) {
+      // The last defined table of the base system_schema() does not exist yet.
+      // $install_state['base_system_verified'] defaults to FALSE, so the code
+      // following below will use the minimal installer service container.
+      // As soon as the base system is verified here, the installer operates in
+      // a full and regular Drupal environment, without any kind of exceptions.
+    }
+  }
+
+  // Replace services with in-memory and null implementations. This kernel is
+  // replaced with a regular one in drupal_install_system().
+  if (!$install_state['base_system_verified']) {
+    $environment = 'install';
+    $GLOBALS['conf']['container_service_providers']['InstallerServiceProvider'] = 'Drupal\Core\Installer\InstallerServiceProvider';
+  }
+  else {
+    $environment = 'prod';
+  }
+  $GLOBALS['conf']['container_service_providers']['InstallerConfigOverride'] = 'Drupal\Core\Installer\ConfigOverride';
+
+  // Only allow dumping the container once the hash salt has been created.
+  $kernel = InstallerKernel::createFromRequest($request, $class_loader, $environment, (bool) Settings::get('hash_salt', FALSE));
+  $kernel->setSitePath($site_path);
+  $kernel->boot();
+  $container = $kernel->getContainer();
+  // If Drupal is being installed behind a proxy, configure the request.
+  ReverseProxyMiddleware::setSettingsOnRequest($request, Settings::getInstance());
+
+  // Register the file translation service.
+  if (isset($GLOBALS['config']['locale.settings']['translation']['path'])) {
+    $directory = $GLOBALS['config']['locale.settings']['translation']['path'];
+  }
+  else {
+    $directory = $site_path . '/files/translations';
+  }
+  $container->set('string_translator.file_translation', new FileTranslation($directory));
+  $container->get('string_translation')
+    ->addTranslator($container->get('string_translator.file_translation'));
+
+  // Add list of all available profiles to the installation state.
+  $listing = new ExtensionDiscovery($container->get('app.root'));
+  $listing->setProfileDirectories([]);
+  $install_state['profiles'] += $listing->scan('profile');
+
+  // Prime drupal_get_filename()'s static cache.
+  foreach ($install_state['profiles'] as $name => $profile) {
+    drupal_get_filename('profile', $name, $profile->getPathname());
+  }
+
+  if ($profile = _install_select_profile($install_state)) {
+    $install_state['parameters']['profile'] = $profile;
+    install_load_profile($install_state);
+    if (isset($install_state['profile_info']['distribution']['install']['theme'])) {
+      $install_state['theme'] = $install_state['profile_info']['distribution']['install']['theme'];
+    }
+  }
+
+  // Use the language from the profile configuration, if available, to override
+  // the language previously set in the parameters.
+  if (isset($install_state['profile_info']['distribution']['langcode'])) {
+    $install_state['parameters']['langcode'] = $install_state['profile_info']['distribution']['langcode'];
+  }
+
+  // Set the default language to the selected language, if any.
+  if (isset($install_state['parameters']['langcode'])) {
+    $default_language = new Language(['id' => $install_state['parameters']['langcode']]);
+    $container->get('language.default')->set($default_language);
+    \Drupal::translation()->setDefaultLangcode($install_state['parameters']['langcode']);
+  }
+
+  // Override the module list with a minimal set of modules.
+  $module_handler = \Drupal::moduleHandler();
+  if (!$module_handler->moduleExists('system')) {
+    $module_handler->addModule('system', 'core/modules/system');
+  }
+  if ($profile && !$module_handler->moduleExists($profile)) {
+    $module_handler->addProfile($profile, $install_state['profiles'][$profile]->getPath());
+  }
+
+  // Load all modules and perform request related initialization.
+  $kernel->preHandle($request);
+
+  // Initialize a route on this legacy request similar to
+  // \Drupal\Core\DrupalKernel::prepareLegacyRequest() since normal routing
+  // will not happen.
+  $request->attributes->set(RouteObjectInterface::ROUTE_OBJECT, new Route('<none>'));
+  $request->attributes->set(RouteObjectInterface::ROUTE_NAME, '<none>');
+
+  // Prepare for themed output. We need to run this at the beginning of the
+  // page request to avoid a different theme accidentally getting set. (We also
+  // need to run it even in the case of command-line installations, to prevent
+  // any code in the installer that happens to initialize the theme system from
+  // accessing the database before it is set up yet.)
+  drupal_maintenance_theme();
+
+  if ($install_state['database_verified']) {
+    // Verify the last completed task in the database, if there is one.
+    $task = install_verify_completed_task();
+  }
+  else {
+    $task = NULL;
+
+    // Do not install over a configured settings.php.
+    if (Database::getConnectionInfo()) {
+      throw new AlreadyInstalledException($container->get('string_translation'));
+    }
+  }
+
+  // Ensure that the active configuration is empty before installation starts.
+  if ($install_state['config_verified'] && empty($task)) {
+    if (count($kernel->getConfigStorage()->listAll())) {
+      $task = NULL;
+      throw new AlreadyInstalledException($container->get('string_translation'));
+    }
+  }
+
+  // Modify the installation state as appropriate.
+  $install_state['completed_task'] = $task;
+}
+
+/**
+ * Runs all tasks for the current installation request.
+ *
+ * In the case of an interactive installation, all tasks will be attempted
+ * until one is reached that has output which needs to be displayed to the
+ * user, or until a page redirect is required. Otherwise, tasks will be
+ * attempted until the installation is finished.
+ *
+ * @param $install_state
+ *   An array of information about the current installation state. This is
+ *   passed along to each task, so it can be modified if necessary.
+ *
+ * @return
+ *   HTML output from the last completed task.
+ */
+function install_run_tasks(&$install_state) {
+  do {
+    // Obtain a list of tasks to perform. The list of tasks itself can be
+    // dynamic (e.g., some might be defined by the installation profile,
+    // which is not necessarily known until the earlier tasks have run),
+    // so we regenerate the remaining tasks based on the installation state,
+    // each time through the loop.
+    $tasks_to_perform = install_tasks_to_perform($install_state);
+    // Run the first task on the list.
+    reset($tasks_to_perform);
+    $task_name = key($tasks_to_perform);
+    $task = array_shift($tasks_to_perform);
+    $install_state['active_task'] = $task_name;
+    $original_parameters = $install_state['parameters'];
+    $output = install_run_task($task, $install_state);
+    // Ensure the maintenance theme is initialized. If the install task has
+    // rebuilt the container the active theme will not be set. This can occur if
+    // the task has installed a module.
+    drupal_maintenance_theme();
+
+    $install_state['parameters_changed'] = ($install_state['parameters'] != $original_parameters);
+    // Store this task as having been performed during the current request,
+    // and save it to the database as completed, if we need to and if the
+    // database is in a state that allows us to do so. Also mark the
+    // installation as 'done' when we have run out of tasks.
+    if (!$install_state['task_not_complete']) {
+      $install_state['tasks_performed'][] = $task_name;
+      $install_state['installation_finished'] = empty($tasks_to_perform);
+      if ($task['run'] == INSTALL_TASK_RUN_IF_NOT_COMPLETED || $install_state['installation_finished']) {
+        \Drupal::state()->set('install_task', $install_state['installation_finished'] ? 'done' : $task_name);
+      }
+    }
+    // Stop when there are no tasks left. In the case of an interactive
+    // installation, also stop if we have some output to send to the browser,
+    // the URL parameters have changed, or an end to the page request was
+    // specifically called for.
+    $finished = empty($tasks_to_perform) || ($install_state['interactive'] && (isset($output) || $install_state['parameters_changed'] || $install_state['stop_page_request']));
+  } while (!$finished);
+  return $output;
+}
+
+/**
+ * Runs an individual installation task.
+ *
+ * @param $task
+ *   An array of information about the task to be run as returned by
+ *   hook_install_tasks().
+ * @param $install_state
+ *   An array of information about the current installation state. This is
+ *   passed in by reference so that it can be modified by the task.
+ *
+ * @return
+ *   The output of the task function, if there is any.
+ */
+function install_run_task($task, &$install_state) {
+  $function = $task['function'];
+
+  if ($task['type'] == 'form') {
+    return install_get_form($function, $install_state);
+  }
+  elseif ($task['type'] == 'batch') {
+    // Start a new batch based on the task function, if one is not running
+    // already.
+    $current_batch = \Drupal::state()->get('install_current_batch');
+    if (!$install_state['interactive'] || !$current_batch) {
+      $batches = $function($install_state);
+      if (empty($batches)) {
+        // If the task did some processing and decided no batch was necessary,
+        // there is nothing more to do here.
+        return;
+      }
+      // Create a one item list of batches if only one batch was provided.
+      if (isset($batches['operations'])) {
+        $batches = [$batches];
+      }
+      foreach ($batches as $batch) {
+        batch_set($batch);
+        // For interactive batches, we need to store the fact that this batch
+        // task is currently running. Otherwise, we need to make sure the batch
+        // will complete in one page request.
+        if ($install_state['interactive']) {
+          \Drupal::state()->set('install_current_batch', $function);
+        }
+        else {
+          $batch =& batch_get();
+          $batch['progressive'] = FALSE;
+        }
+      }
+      // Process the batch. For progressive batches, this will redirect.
+      // Otherwise, the batch will complete.
+      // Disable the default script for the URL and clone the object, as
+      // batch_process() will add additional options to the batch URL.
+      $url = Url::fromUri('base:install.php', ['query' => $install_state['parameters'], 'script' => '']);
+      $response = batch_process($url, clone $url);
+      if ($response instanceof Response) {
+        if ($session = \Drupal::request()->getSession()) {
+          $session->save();
+        }
+        // Send the response.
+        $response->send();
+        exit;
+      }
+    }
+    // If we are in the middle of processing this batch, keep sending back
+    // any output from the batch process, until the task is complete.
+    elseif ($current_batch == $function) {
+      $output = _batch_page(\Drupal::request());
+      // Because Batch API now returns a JSON response for intermediary steps,
+      // but the installer doesn't handle Response objects yet, just send the
+      // output here and emulate the old model.
+      // @todo Replace this when we refactor the installer to use a request-
+      //   response workflow.
+      if ($output instanceof Response) {
+        $output->send();
+        $output = NULL;
+      }
+      // The task is complete when we try to access the batch page and receive
+      // FALSE in return, since this means we are at a URL where we are no
+      // longer requesting a batch ID.
+      if ($output === FALSE) {
+        // Return nothing so the next task will run in the same request.
+        \Drupal::state()->delete('install_current_batch');
+        return;
+      }
+      else {
+        // We need to force the page request to end if the task is not
+        // complete, since the batch API sometimes prints JSON output
+        // rather than returning a themed page.
+        $install_state['task_not_complete'] = $install_state['stop_page_request'] = TRUE;
+        return $output;
+      }
+    }
+  }
+
+  else {
+    // For normal tasks, just return the function result, whatever it is.
+    return $function($install_state);
+  }
+}
+
+/**
+ * Returns a list of tasks to perform during the current installation request.
+ *
+ * Note that the list of tasks can change based on the installation state as
+ * the page request evolves (for example, if an installation profile hasn't
+ * been selected yet, we don't yet know which profile tasks need to be run).
+ *
+ * @param $install_state
+ *   An array of information about the current installation state.
+ *
+ * @return
+ *   A list of tasks to be performed, with associated metadata.
+ */
+function install_tasks_to_perform($install_state) {
+  // Start with a list of all currently available tasks.
+  $tasks = install_tasks($install_state);
+  foreach ($tasks as $name => $task) {
+    // Remove any tasks that were already performed or that never should run.
+    // Also, if we started this page request with an indication of the last
+    // task that was completed, skip that task and all those that come before
+    // it, unless they are marked as always needing to run.
+    if ($task['run'] == INSTALL_TASK_SKIP || in_array($name, $install_state['tasks_performed']) || (!empty($install_state['completed_task']) && empty($completed_task_found) && $task['run'] != INSTALL_TASK_RUN_IF_REACHED)) {
+      unset($tasks[$name]);
+    }
+    if (!empty($install_state['completed_task']) && $name == $install_state['completed_task']) {
+      $completed_task_found = TRUE;
+    }
+  }
+  return $tasks;
+}
+
+/**
+ * Returns a list of all tasks the installer currently knows about.
+ *
+ * This function will return tasks regardless of whether or not they are
+ * intended to run on the current page request. However, the list can change
+ * based on the installation state (for example, if an installation profile
+ * hasn't been selected yet, we don't yet know which profile tasks will be
+ * available).
+ *
+ * You can override this using hook_install_tasks() or
+ * hook_install_tasks_alter().
+ *
+ * @param $install_state
+ *   An array of information about the current installation state.
+ *
+ * @return
+ *   A list of tasks, with associated metadata as returned by
+ *   hook_install_tasks().
+ */
+function install_tasks($install_state) {
+  // Determine whether a translation file must be imported during the
+  // 'install_import_translations' task. Import when a non-English language is
+  // available and selected. Also we will need translations even if the
+  // installer language is English but there are other languages on the system.
+  $needs_translations = (count($install_state['translations']) > 1 && !empty($install_state['parameters']['langcode']) && $install_state['parameters']['langcode'] != 'en') || \Drupal::languageManager()->isMultilingual();
+  // Determine whether a translation file must be downloaded during the
+  // 'install_download_translation' task. Download when a non-English language
+  // is selected, but no translation is yet in the translations directory.
+  $needs_download = isset($install_state['parameters']['langcode']) && !isset($install_state['translations'][$install_state['parameters']['langcode']]) && $install_state['parameters']['langcode'] != 'en';
+
+  // Start with the core installation tasks that run before handing control
+  // to the installation profile.
+  $tasks = [
+    'install_select_language' => [
+      'display_name' => t('Choose language'),
+      'run' => INSTALL_TASK_RUN_IF_REACHED,
+    ],
+    'install_download_translation' => [
+      'run' => $needs_download ? INSTALL_TASK_RUN_IF_REACHED : INSTALL_TASK_SKIP,
+    ],
+    'install_select_profile' => [
+      'display_name' => t('Choose profile'),
+      'display' => empty($install_state['profile_info']['distribution']['name']) && count($install_state['profiles']) != 1,
+      'run' => INSTALL_TASK_RUN_IF_REACHED,
+    ],
+    'install_load_profile' => [
+      'run' => INSTALL_TASK_RUN_IF_REACHED,
+    ],
+    'install_verify_requirements' => [
+      'display_name' => t('Verify requirements'),
+    ],
+    'install_settings_form' => [
+      'display_name' => t('Set up database'),
+      'type' => 'form',
+      // Even though the form only allows the user to enter database settings,
+      // we still need to display it if settings.php is invalid in any way,
+      // since the form submit handler is where settings.php is rewritten.
+      'run' => $install_state['settings_verified'] ? INSTALL_TASK_SKIP : INSTALL_TASK_RUN_IF_NOT_COMPLETED,
+      'function' => 'Drupal\Core\Installer\Form\SiteSettingsForm',
+    ],
+    'install_write_profile' => [],
+    'install_verify_database_ready' => [
+      'run' => $install_state['database_ready'] ? INSTALL_TASK_SKIP : INSTALL_TASK_RUN_IF_NOT_COMPLETED,
+    ],
+    'install_base_system' => [
+      'run' => $install_state['base_system_verified'] ? INSTALL_TASK_SKIP : INSTALL_TASK_RUN_IF_NOT_COMPLETED,
+    ],
+    // All tasks below are executed in a regular, full Drupal environment.
+    'install_bootstrap_full' => [
+      'run' => INSTALL_TASK_RUN_IF_REACHED,
+    ],
+    'install_profile_modules' => [
+      'display_name' => t('Install site'),
+      'type' => 'batch',
+    ],
+    'install_profile_themes' => [],
+    'install_install_profile' => [],
+    'install_import_translations' => [
+      'display_name' => t('Set up translations'),
+      'display' => $needs_translations,
+      'type' => 'batch',
+      'run' => $needs_translations ? INSTALL_TASK_RUN_IF_NOT_COMPLETED : INSTALL_TASK_SKIP,
+    ],
+    'install_configure_form' => [
+      'display_name' => t('Configure site'),
+      'type' => 'form',
+      'function' => 'Drupal\Core\Installer\Form\SiteConfigureForm',
+    ],
+  ];
+
+  // Now add any tasks defined by the installation profile.
+  if (!empty($install_state['parameters']['profile'])) {
+    // Load the profile install file, because it is not always loaded when
+    // hook_install_tasks() is invoked (e.g. batch processing).
+    $profile = $install_state['parameters']['profile'];
+    $profile_install_file = $install_state['profiles'][$profile]->getPath() . '/' . $profile . '.install';
+    if (file_exists($profile_install_file)) {
+      include_once \Drupal::root() . '/' . $profile_install_file;
+    }
+    $function = $install_state['parameters']['profile'] . '_install_tasks';
+    if (function_exists($function)) {
+      $result = $function($install_state);
+      if (is_array($result)) {
+        $tasks += $result;
+      }
+    }
+  }
+
+  // Finish by adding the remaining core tasks.
+  $tasks += [
+    'install_finish_translations' => [
+      'display_name' => t('Finish translations'),
+      'display' => $needs_translations,
+      'type' => 'batch',
+      'run' => $needs_translations ? INSTALL_TASK_RUN_IF_NOT_COMPLETED : INSTALL_TASK_SKIP,
+    ],
+    'install_finished' => [],
+  ];
+
+  // Allow the installation profile to modify the full list of tasks.
+  if (!empty($install_state['parameters']['profile'])) {
+    $profile = $install_state['parameters']['profile'];
+    if ($install_state['profiles'][$profile]->load()) {
+      $function = $install_state['parameters']['profile'] . '_install_tasks_alter';
+      if (function_exists($function)) {
+        $function($tasks, $install_state);
+      }
+    }
+  }
+
+  // Fill in default parameters for each task before returning the list.
+  foreach ($tasks as $task_name => &$task) {
+    $task += [
+      'display_name' => NULL,
+      'display' => !empty($task['display_name']),
+      'type' => 'normal',
+      'run' => INSTALL_TASK_RUN_IF_NOT_COMPLETED,
+      'function' => $task_name,
+    ];
+  }
+  return $tasks;
+}
+
+/**
+ * Returns a list of tasks that should be displayed to the end user.
+ *
+ * The output of this function is a list suitable for sending to
+ * maintenance-task-list.html.twig.
+ *
+ * @param $install_state
+ *   An array of information about the current installation state.
+ *
+ * @return
+ *   A list of tasks, with keys equal to the machine-readable task name and
+ *   values equal to the name that should be displayed.
+ *
+ * @see maintenance-task-list.html.twig
+ */
+function install_tasks_to_display($install_state) {
+  $displayed_tasks = [];
+  foreach (install_tasks($install_state) as $name => $task) {
+    if ($task['display']) {
+      $displayed_tasks[$name] = $task['display_name'];
+    }
+  }
+  return $displayed_tasks;
+}
+
+/**
+ * Builds and processes a form for the installer environment.
+ *
+ * Ensures that FormBuilder does not redirect after submitting a form, since the
+ * installer uses a custom step/flow logic via install_run_tasks().
+ *
+ * @param string|array $form_id
+ *   The form ID to build and process.
+ * @param array $install_state
+ *   The current state of the installation.
+ *
+ * @return array|null
+ *   A render array containing the form to render, or NULL in case the form was
+ *   successfully submitted.
+ *
+ * @throws \Drupal\Core\Installer\Exception\InstallerException
+ */
+function install_get_form($form_id, array &$install_state) {
+  // Ensure the form will not redirect, since install_run_tasks() uses a custom
+  // redirection logic.
+  $form_state = (new FormState())
+    ->addBuildInfo('args', [&$install_state])
+    ->disableRedirect();
+  $form_builder = \Drupal::formBuilder();
+  if ($install_state['interactive']) {
+    $form = $form_builder->buildForm($form_id, $form_state);
+    // If the form submission was not successful, the form needs to be rendered,
+    // which means the task is not complete yet.
+    if (!$form_state->isExecuted()) {
+      $install_state['task_not_complete'] = TRUE;
+      return $form;
+    }
+  }
+  else {
+    // For non-interactive installs, submit the form programmatically with the
+    // values taken from the installation state.
+    $install_form_id = $form_builder->getFormId($form_id, $form_state);
+    if (!empty($install_state['forms'][$install_form_id])) {
+      $form_state->setValues($install_state['forms'][$install_form_id]);
+    }
+    $form_builder->submitForm($form_id, $form_state);
+
+    // Throw an exception in case of any form validation error.
+    if ($errors = $form_state->getErrors()) {
+      throw new InstallerException(implode("\n", $errors));
+    }
+  }
+}
+
+/**
+ * Returns the URL that should be redirected to during an installation request.
+ *
+ * The output of this function is suitable for sending to install_goto().
+ *
+ * @param $install_state
+ *   An array of information about the current installation state.
+ *
+ * @return
+ *   The URL to redirect to.
+ *
+ * @see install_full_redirect_url()
+ */
+function install_redirect_url($install_state) {
+  return 'core/install.php?' . UrlHelper::buildQuery($install_state['parameters']);
+}
+
+/**
+ * Returns the complete URL redirected to during an installation request.
+ *
+ * @param $install_state
+ *   An array of information about the current installation state.
+ *
+ * @return
+ *   The complete URL to redirect to.
+ *
+ * @see install_redirect_url()
+ */
+function install_full_redirect_url($install_state) {
+  global $base_url;
+  return $base_url . '/' . install_redirect_url($install_state);
+}
+
+/**
+ * Displays themed installer output and ends the page request.
+ *
+ * Installation tasks should use #title to set the desired page
+ * title, but otherwise this function takes care of theming the overall page
+ * output during every step of the installation.
+ *
+ * @param $output
+ *   The content to display on the main part of the page.
+ * @param $install_state
+ *   An array of information about the current installation state.
+ */
+function install_display_output($output, $install_state) {
+  // Ensure the maintenance theme is initialized.
+  // The regular initialization call in install_begin_request() may not be
+  // reached in case of an early installer error.
+  drupal_maintenance_theme();
+
+  // Prevent install.php from being indexed when installed in a sub folder.
+  // robots.txt rules are not read if the site is within domain.com/subfolder
+  // resulting in /subfolder/install.php being found through search engines.
+  // When settings.php is writeable this can be used via an external database
+  // leading a malicious user to gain php access to the server.
+  $noindex_meta_tag = [
+    '#tag' => 'meta',
+    '#attributes' => [
+      'name' => 'robots',
+      'content' => 'noindex, nofollow',
+    ],
+  ];
+  $output['#attached']['html_head'][] = [$noindex_meta_tag, 'install_meta_robots'];
+
+  // Only show the task list if there is an active task; otherwise, the page
+  // request has ended before tasks have even been started, so there is nothing
+  // meaningful to show.
+  $regions = [];
+  if (isset($install_state['active_task'])) {
+    // Let the theming function know when every step of the installation has
+    // been completed.
+    $active_task = $install_state['installation_finished'] ? NULL : $install_state['active_task'];
+    $task_list = [
+      '#theme' => 'maintenance_task_list',
+      '#items' => install_tasks_to_display($install_state),
+      '#active' => $active_task,
+    ];
+    $regions['sidebar_first'] = $task_list;
+  }
+
+  $bare_html_page_renderer = \Drupal::service('bare_html_page_renderer');
+  $response = $bare_html_page_renderer->renderBarePage($output, $output['#title'], 'install_page', $regions);
+  $default_headers = [
+    'Expires' => 'Sun, 19 Nov 1978 05:00:00 GMT',
+    'Last-Modified' => gmdate(DATE_RFC1123, REQUEST_TIME),
+    'Cache-Control' => 'no-cache, must-revalidate',
+    'ETag' => '"' . REQUEST_TIME . '"',
+  ];
+  $response->headers->add($default_headers);
+  $response->send();
+  exit;
+}
+
+/**
+ * Verifies the requirements for installing Drupal.
+ *
+ * @param $install_state
+ *   An array of information about the current installation state.
+ *
+ * @return
+ *   A themed status report, or an exception if there are requirement errors.
+ */
+function install_verify_requirements(&$install_state) {
+  // Check the installation requirements for Drupal and this profile.
+  $requirements = install_check_requirements($install_state);
+
+  // Verify existence of all required modules.
+  $requirements += drupal_verify_profile($install_state);
+
+  return install_display_requirements($install_state, $requirements);
+}
+
+/**
+ * Installation task; install the base functionality Drupal needs to bootstrap.
+ *
+ * @param $install_state
+ *   An array of information about the current installation state.
+ */
+function install_base_system(&$install_state) {
+  // Install system.module.
+  drupal_install_system($install_state);
+
+  // Prevent the installer from using the system temporary directory after the
+  // system module has been installed.
+  if (drupal_valid_test_ua()) {
+    // While the temporary directory could be preset/enforced in settings.php
+    // like the public files directory, some tests expect it to be configurable
+    // in the UI. If declared in settings.php, they would no longer be
+    // configurable. The temporary directory needs to match what is set in each
+    // test types ::prepareEnvironment() step.
+    $temporary_directory = dirname(PublicStream::basePath()) . '/temp';
+    file_prepare_directory($temporary_directory, FILE_MODIFY_PERMISSIONS | FILE_CREATE_DIRECTORY);
+    \Drupal::configFactory()->getEditable('system.file')
+      ->set('path.temporary', $temporary_directory)
+      ->save();
+  }
+
+  // Call file_ensure_htaccess() to ensure that all of Drupal's standard
+  // directories (e.g., the public files directory and config directory) have
+  // appropriate .htaccess files. These directories will have already been
+  // created by this point in the installer, since Drupal creates them during
+  // the install_verify_requirements() task. Note that we cannot call
+  // file_ensure_access() any earlier than this, since it relies on
+  // system.module in order to work.
+  file_ensure_htaccess();
+
+  // Prime the drupal_get_filename() static cache with the user module's
+  // exact location.
+  // @todo Remove as part of https://www.drupal.org/node/2186491
+  drupal_get_filename('module', 'user', 'core/modules/user/user.info.yml');
+
+  // Enable the user module so that sessions can be recorded during the
+  // upcoming bootstrap step.
+  \Drupal::service('module_installer')->install(['user'], FALSE);
+
+  // Save the list of other modules to install for the upcoming tasks.
+  // State can be set to the database now that system.module is installed.
+  $modules = $install_state['profile_info']['dependencies'];
+
+  \Drupal::state()->set('install_profile_modules', array_diff($modules, ['system']));
+  $install_state['base_system_verified'] = TRUE;
+}
+
+/**
+ * Verifies and returns the last installation task that was completed.
+ *
+ * @return
+ *   The last completed task, if there is one. An exception is thrown if Drupal
+ *   is already installed.
+ */
+function install_verify_completed_task() {
+  try {
+    $task = \Drupal::state()->get('install_task');
+  }
+  // Do not trigger an error if the database query fails, since the database
+  // might not be set up yet.
+  catch (\Exception $e) {
+  }
+  if (isset($task)) {
+    if ($task == 'done') {
+      throw new AlreadyInstalledException(\Drupal::service('string_translation'));
+    }
+    return $task;
+  }
+}
+
+/**
+ * Verifies that settings.php specifies a valid database connection.
+ *
+ * @param string $site_path
+ *   The site path.
+ *
+ * @return bool
+ *   TRUE if there are no database errors.
+ */
+function install_verify_database_settings($site_path) {
+  if ($database = Database::getConnectionInfo()) {
+    $database = $database['default'];
+    $settings_file = './' . $site_path . '/settings.php';
+    $errors = install_database_errors($database, $settings_file);
+    if (empty($errors)) {
+      return TRUE;
+    }
+  }
+  return FALSE;
+}
+
+/**
+ * Verify that the database is ready (no existing Drupal installation).
+ */
+function install_verify_database_ready() {
+  $system_schema = system_schema();
+  end($system_schema);
+  $table = key($system_schema);
+
+  if ($database = Database::getConnectionInfo()) {
+    if (Database::getConnection()->schema()->tableExists($table)) {
+      throw new AlreadyInstalledException(\Drupal::service('string_translation'));
+    }
+  }
+}
+
+/**
+ * Checks a database connection and returns any errors.
+ */
+function install_database_errors($database, $settings_file) {
+  $errors = [];
+
+  // Check database type.
+  $database_types = drupal_get_database_types();
+  $driver = $database['driver'];
+  if (!isset($database_types[$driver])) {
+    $errors['driver'] = t("In your %settings_file file you have configured @drupal to use a %driver server, however your PHP installation currently does not support this database type.", ['%settings_file' => $settings_file, '@drupal' => drupal_install_profile_distribution_name(), '%driver' => $driver]);
+  }
+  else {
+    // Run driver specific validation
+    $errors += $database_types[$driver]->validateDatabaseSettings($database);
+    if (!empty($errors)) {
+      // No point to try further.
+      return $errors;
+    }
+    // Run tasks associated with the database type. Any errors are caught in the
+    // calling function.
+    Database::addConnectionInfo('default', 'default', $database);
+
+    $errors = db_installer_object($driver)->runTasks();
+  }
+  return $errors;
+}
+
+/**
+ * Selects which profile to install.
+ *
+ * @param $install_state
+ *   An array of information about the current installation state. The chosen
+ *   profile will be added here, if it was not already selected previously, as
+ *   will a list of all available profiles.
+ *
+ * @return
+ *   For interactive installations, a form allowing the profile to be selected,
+ *   if the user has a choice that needs to be made. Otherwise, an exception is
+ *   thrown if a profile cannot be chosen automatically.
+ */
+function install_select_profile(&$install_state) {
+  if (empty($install_state['parameters']['profile'])) {
+    // If there are no profiles at all, installation cannot proceed.
+    if (empty($install_state['profiles'])) {
+      throw new NoProfilesException(\Drupal::service('string_translation'));
+    }
+    // Try to automatically select a profile.
+    if ($profile = _install_select_profile($install_state)) {
+      $install_state['parameters']['profile'] = $profile;
+    }
+    else {
+      // The non-interactive installer requires a profile parameter.
+      if (!$install_state['interactive']) {
+        throw new InstallerException(t('Missing profile parameter.'));
+      }
+      // Otherwise, display a form to select a profile.
+      return install_get_form('Drupal\Core\Installer\Form\SelectProfileForm', $install_state);
+    }
+  }
+}
+
+/**
+ * Determines the installation profile to use in the installer.
+ *
+ * A profile will be selected in the following order of conditions:
+ * - Only one profile is available.
+ * - A specific profile name is requested in installation parameters:
+ *   - For interactive installations via request query parameters.
+ *   - For non-interactive installations via install_drupal() settings.
+ * - A discovered profile that is a distribution. If multiple profiles are
+ *   distributions, then the first discovered profile will be selected.
+ * - Only one visible profile is available.
+ *
+ * @param array $install_state
+ *   The current installer state, containing a 'profiles' key, which is an
+ *   associative array of profiles with the machine-readable names as keys.
+ *
+ * @return
+ *   The machine-readable name of the selected profile or NULL if no profile was
+ *   selected.
+ */
+function _install_select_profile(&$install_state) {
+  // Don't need to choose profile if only one available.
+  if (count($install_state['profiles']) == 1) {
+    return key($install_state['profiles']);
+  }
+  if (!empty($install_state['parameters']['profile'])) {
+    $profile = $install_state['parameters']['profile'];
+    if (isset($install_state['profiles'][$profile])) {
+      return $profile;
+    }
+  }
+  // Check for a distribution profile.
+  foreach ($install_state['profiles'] as $profile) {
+    $profile_info = install_profile_info($profile->getName());
+    if (!empty($profile_info['distribution'])) {
+      return $profile->getName();
+    }
+  }
+
+  // Get all visible (not hidden) profiles.
+  $visible_profiles = array_filter($install_state['profiles'], function ($profile) {
+    $profile_info = install_profile_info($profile->getName());
+    return !isset($profile_info['hidden']) || !$profile_info['hidden'];
+  });
+
+  if (count($visible_profiles) == 1) {
+    return (key($visible_profiles));
+  }
+}
+
+/**
+ * Finds all .po files that are useful to the installer.
+ *
+ * @return
+ *   An associative array of file URIs keyed by language code. URIs as
+ *   returned by file_scan_directory().
+ *
+ * @see file_scan_directory()
+ */
+function install_find_translations() {
+  $translations = [];
+  $files = \Drupal::service('string_translator.file_translation')->findTranslationFiles();
+  // English does not need a translation file.
+  array_unshift($files, (object) ['name' => 'en']);
+  foreach ($files as $uri => $file) {
+    // Strip off the file name component before the language code.
+    $langcode = preg_replace('!^(.+\.)?([^\.]+)$!', '\2', $file->name);
+    // Language codes cannot exceed 12 characters to fit into the {language}
+    // table.
+    if (strlen($langcode) <= 12) {
+      $translations[$langcode] = $uri;
+    }
+  }
+  return $translations;
+}
+
+/**
+ * Selects which language to use during installation.
+ *
+ * @param $install_state
+ *   An array of information about the current installation state. The chosen
+ *   langcode will be added here, if it was not already selected previously, as
+ *   will a list of all available languages.
+ *
+ * @return
+ *   For interactive installations, a form or other page output allowing the
+ *   language to be selected or providing information about language selection,
+ *   if a language has not been chosen. Otherwise, an exception is thrown if a
+ *   language cannot be chosen automatically.
+ */
+function install_select_language(&$install_state) {
+  // Find all available translation files.
+  $files = install_find_translations();
+  $install_state['translations'] += $files;
+
+  // If a valid language code is set, continue with the next installation step.
+  // When translations from the localization server are used, any language code
+  // is accepted because the standard language list is kept in sync with the
+  // languages available at http://localize.drupal.org.
+  // When files from the translation directory are used, we only accept
+  // languages for which a file is available.
+  if (!empty($install_state['parameters']['langcode'])) {
+    $standard_languages = LanguageManager::getStandardLanguageList();
+    $langcode = $install_state['parameters']['langcode'];
+    if ($langcode == 'en' || isset($files[$langcode]) || isset($standard_languages[$langcode])) {
+      $install_state['parameters']['langcode'] = $langcode;
+      return;
+    }
+  }
+
+  if (empty($install_state['parameters']['langcode'])) {
+    // If we are performing an interactive installation, we display a form to
+    // select a right language. If no translation files were found in the
+    // translations directory, the form shows a list of standard languages. If
+    // translation files were found the form shows a select list of the
+    // corresponding languages to choose from.
+    if ($install_state['interactive']) {
+      return install_get_form('Drupal\Core\Installer\Form\SelectLanguageForm', $install_state);
+    }
+    // If we are performing a non-interactive installation. If only one language
+    // (English) is available, assume the user knows what he is doing. Otherwise
+    // throw an error.
+    else {
+      if (count($files) == 1) {
+        $install_state['parameters']['langcode'] = current(array_keys($files));
+        return;
+      }
+      else {
+        throw new InstallerException(t('You must select a language to continue the installation.'));
+      }
+    }
+  }
+}
+
+/**
+ * Download a translation file for the selected language.
+ *
+ * @param array $install_state
+ *   An array of information about the current installation state.
+ *
+ * @return string
+ *   A themed status report, or an exception if there are requirement errors.
+ *   Upon successful download the page is reloaded and no output is returned.
+ */
+function install_download_translation(&$install_state) {
+  // Check whether all conditions are met to download. Download the translation
+  // if possible.
+  $requirements = install_check_translations($install_state['parameters']['langcode'], $install_state['server_pattern']);
+  if ($output = install_display_requirements($install_state, $requirements)) {
+    return $output;
+  }
+
+  // The download was successful, reload the page in the new language.
+  $install_state['translations'][$install_state['parameters']['langcode']] = TRUE;
+  if ($install_state['interactive']) {
+    install_goto(install_redirect_url($install_state));
+  }
+}
+
+/**
+ * Attempts to get a file using a HTTP request and to store it locally.
+ *
+ * @param string $uri
+ *   The URI of the file to grab.
+ * @param string $destination
+ *   Stream wrapper URI specifying where the file should be placed. If a
+ *   directory path is provided, the file is saved into that directory under its
+ *   original name. If the path contains a filename as well, that one will be
+ *   used instead.
+ *
+ * @return bool
+ *   TRUE on success, FALSE on failure.
+ */
+function install_retrieve_file($uri, $destination) {
+  $parsed_url = parse_url($uri);
+  if (is_dir(\Drupal::service('file_system')->realpath($destination))) {
+    // Prevent URIs with triple slashes when gluing parts together.
+    $path = str_replace('///', '//', "$destination/") . drupal_basename($parsed_url['path']);
+  }
+  else {
+    $path = $destination;
+  }
+
+  try {
+    $response = \Drupal::httpClient()->get($uri, ['headers' => ['Accept' => 'text/plain']]);
+    $data = (string) $response->getBody();
+    if (empty($data)) {
+      return FALSE;
+    }
+  }
+  catch (RequestException $e) {
+    return FALSE;
+  }
+  return file_put_contents($path, $data) !== FALSE;
+}
+
+/**
+ * Checks if the localization server can be contacted.
+ *
+ * @param string $uri
+ *   The URI to contact.
+ *
+ * @return string
+ *   TRUE if the URI was contacted successfully, FALSE if not.
+ */
+function install_check_localization_server($uri) {
+  try {
+    \Drupal::httpClient()->head($uri);
+    return TRUE;
+  }
+  catch (RequestException $e) {
+    return FALSE;
+  }
+}
+
+/**
+ * Extracts version information from a drupal core version string.
+ *
+ * @param string $version
+ *   Version info string (e.g., 8.0.0, 8.1.0, 8.0.0-dev, 8.0.0-unstable1,
+ *   8.0.0-alpha2, 8.0.0-beta3, 8.6.x, and 8.0.0-rc4).
+ *
+ * @return array
+ *   Associative array of version info:
+ *   - major: Major version (e.g., "8").
+ *   - minor: Minor version (e.g., "0").
+ *   - patch: Patch version (e.g., "0").
+ *   - extra: Extra version info (e.g., "alpha2").
+ *   - extra_text: The text part of "extra" (e.g., "alpha").
+ *   - extra_number: The number part of "extra" (e.g., "2").
+ */
+function _install_get_version_info($version) {
+  preg_match('/
+    (
+      (?P<major>[0-9]+)    # Major release number.
+      \.          # .
+      (?P<minor>[0-9]+)    # Minor release number.
+      \.          # .
+      (?P<patch>[0-9]+|x)  # Patch release number.
+    )             #
+    (             #
+      -           # - separator for "extra" version information.
+      (?P<extra>   #
+        (?P<extra_text>[a-z]+)  # Release extra text (e.g., "alpha").
+        (?P<extra_number>[0-9]*)  # Release extra number (no separator between text and number).
+      )           #
+      |           # OR no "extra" information.
+    )
+    /sx', $version, $matches);
+
+  return $matches;
+}
+
+/**
+ * Loads information about the chosen profile during installation.
+ *
+ * @param $install_state
+ *   An array of information about the current installation state. The loaded
+ *   profile information will be added here.
+ */
+function install_load_profile(&$install_state) {
+  $profile = $install_state['parameters']['profile'];
+  $install_state['profiles'][$profile]->load();
+  $install_state['profile_info'] = install_profile_info($profile, isset($install_state['parameters']['langcode']) ? $install_state['parameters']['langcode'] : 'en');
+}
+
+/**
+ * Performs a full bootstrap of Drupal during installation.
+ */
+function install_bootstrap_full() {
+  // Store the session on the request object and start it.
+  /** @var \Symfony\Component\HttpFoundation\Session\SessionInterface $session */
+  $session = \Drupal::service('session');
+  \Drupal::request()->setSession($session);
+  $session->start();
+}
+
+/**
+ * Installs required modules via a batch process.
+ *
+ * @param $install_state
+ *   An array of information about the current installation state.
+ *
+ * @return
+ *   The batch definition.
+ */
+function install_profile_modules(&$install_state) {
+  // We need to manually trigger the installation of core-provided entity types,
+  // as those will not be handled by the module installer.
+  install_core_entity_type_definitions();
+
+  $modules = \Drupal::state()->get('install_profile_modules') ?: [];
+  $files = system_rebuild_module_data();
+  \Drupal::state()->delete('install_profile_modules');
+
+  // Always install required modules first. Respect the dependencies between
+  // the modules.
+  $required = [];
+  $non_required = [];
+
+  // Add modules that other modules depend on.
+  foreach ($modules as $module) {
+    if ($files[$module]->requires) {
+      $modules = array_merge($modules, array_keys($files[$module]->requires));
+    }
+  }
+  $modules = array_unique($modules);
+  foreach ($modules as $module) {
+    if (!empty($files[$module]->info['required'])) {
+      $required[$module] = $files[$module]->sort;
+    }
+    else {
+      $non_required[$module] = $files[$module]->sort;
+    }
+  }
+  arsort($required);
+  arsort($non_required);
+
+  $operations = [];
+  foreach ($required + $non_required as $module => $weight) {
+    $operations[] = ['_install_module_batch', [$module, $files[$module]->info['name']]];
+  }
+  $batch = [
+    'operations' => $operations,
+    'title' => t('Installing @drupal', ['@drupal' => drupal_install_profile_distribution_name()]),
+    'error_message' => t('The installation has encountered an error.'),
+  ];
+  return $batch;
+}
+
+/**
+ * Installs entity type definitions provided by core.
+ */
+function install_core_entity_type_definitions() {
+  $update_manager = \Drupal::entityDefinitionUpdateManager();
+  foreach (\Drupal::entityManager()->getDefinitions() as $entity_type) {
+    if ($entity_type->getProvider() == 'core') {
+      $update_manager->installEntityType($entity_type);
+    }
+  }
+}
+
+/**
+ * Installs themes.
+ *
+ * This does not use a batch, since installing themes is faster than modules and
+ * because an installation profile typically installs 1-3 themes only (default
+ * theme, base theme, admin theme).
+ *
+ * @param $install_state
+ *   An array of information about the current installation state.
+ */
+function install_profile_themes(&$install_state) {
+  // Install the themes specified by the installation profile.
+  $themes = $install_state['profile_info']['themes'];
+  \Drupal::service('theme_handler')->install($themes);
+
+  // Ensure that the install profile's theme is used.
+  // @see _drupal_maintenance_theme()
+  \Drupal::theme()->resetActiveTheme();
+}
+
+/**
+ * Installs the install profile.
+ *
+ * @param $install_state
+ *   An array of information about the current installation state.
+ */
+function install_install_profile(&$install_state) {
+  \Drupal::service('module_installer')->install([drupal_get_profile()], FALSE);
+  // Install all available optional config. During installation the module order
+  // is determined by dependencies. If there are no dependencies between modules
+  // then the order in which they are installed is dependent on random factors
+  // like PHP version. Optional configuration therefore might or might not be
+  // created depending on this order. Ensuring that we have installed all of the
+  // optional configuration whose dependencies can be met at this point removes
+  // any disparities that this creates.
+  \Drupal::service('config.installer')->installOptionalConfig();
+
+  // Ensure that the install profile's theme is used.
+  // @see _drupal_maintenance_theme()
+  \Drupal::theme()->resetActiveTheme();
+}
+
+/**
+ * Prepares the system for import and downloads additional translations.
+ *
+ * @param $install_state
+ *   An array of information about the current installation state.
+ *
+ * @return
+ *   The batch definition, if there are language files to download.
+ */
+function install_download_additional_translations_operations(&$install_state) {
+  \Drupal::moduleHandler()->loadInclude('locale', 'bulk.inc');
+
+  $langcode = $install_state['parameters']['langcode'];
+  if (!($language = ConfigurableLanguage::load($langcode))) {
+    // Create the language if not already shipped with a profile.
+    $language = ConfigurableLanguage::createFromLangcode($langcode);
+  }
+  $language->save();
+
+  // If a non-English language was selected, change the default language and
+  // remove English.
+  if ($langcode != 'en') {
+    \Drupal::configFactory()->getEditable('system.site')
+      ->set('langcode', $langcode)
+      ->set('default_langcode', $langcode)
+      ->save();
+    \Drupal::service('language.default')->set($language);
+    if (empty($install_state['profile_info']['keep_english'])) {
+      entity_delete_multiple('configurable_language', ['en']);
+    }
+  }
+
+  // If there is more than one language or the single one is not English, we
+  // should download/import translations.
+  $languages = \Drupal::languageManager()->getLanguages();
+  $operations = [];
+  foreach ($languages as $langcode => $language) {
+    // The installer language was already downloaded. Check downloads for the
+    // other languages if any. Ignore any download errors here, since we
+    // are in the middle of an install process and there is no way back. We
+    // will not import what we cannot download.
+    if ($langcode != 'en' && $langcode != $install_state['parameters']['langcode']) {
+      $operations[] = ['install_check_translations', [$langcode, $install_state['server_pattern']]];
+    }
+  }
+  return $operations;
+}
+
+/**
+ * Imports languages via a batch process during installation.
+ *
+ * @param $install_state
+ *   An array of information about the current installation state.
+ *
+ * @return
+ *   The batch definition, if there are language files to import.
+ */
+function install_import_translations(&$install_state) {
+  \Drupal::moduleHandler()->loadInclude('locale', 'translation.inc');
+
+  // If there is more than one language or the single one is not English, we
+  // should import translations.
+  $operations = install_download_additional_translations_operations($install_state);
+  $languages = \Drupal::languageManager()->getLanguages();
+  if (count($languages) > 1 || !isset($languages['en'])) {
+    $operations[] = ['_install_prepare_import', [array_keys($languages), $install_state['server_pattern']]];
+
+    // Set up a batch to import translations for drupal core. Translation import
+    // for contrib modules happens in install_import_translations_remaining.
+    foreach ($languages as $language) {
+      if (locale_translation_use_remote_source()) {
+        $operations[] = ['locale_translation_batch_fetch_download', ['drupal', $language->getId()]];
+      }
+      $operations[] = ['locale_translation_batch_fetch_import', ['drupal', $language->getId(), []]];
+    }
+
+    module_load_include('fetch.inc', 'locale');
+    $batch = [
+      'operations' => $operations,
+      'title' => t('Updating translations.'),
+      'progress_message' => '',
+      'error_message' => t('Error importing translation files'),
+      'finished' => 'locale_translation_batch_fetch_finished',
+      'file' => drupal_get_path('module', 'locale') . '/locale.batch.inc',
+    ];
+    return $batch;
+  }
+}
+
+/**
+ * Tells the translation import process that Drupal core is installed.
+ *
+ * @param array $langcodes
+ *   Language codes used for the translations.
+ * @param string $server_pattern
+ *   Server access pattern (to replace language code, version number, etc. in).
+ */
+function _install_prepare_import($langcodes, $server_pattern) {
+  \Drupal::moduleHandler()->loadInclude('locale', 'bulk.inc');
+  $matches = [];
+
+  foreach ($langcodes as $langcode) {
+    // Get the translation files located in the translations directory.
+    $files = locale_translate_get_interface_translation_files(['drupal'], [$langcode]);
+    // Pick the first file which matches the language, if any.
+    $file = reset($files);
+    if (is_object($file)) {
+      $filename = $file->filename;
+      preg_match('/drupal-([0-9a-z\.-]+)\.' . $langcode . '\.po/', $filename, $matches);
+      // Get the version information.
+      if ($version = $matches[1]) {
+        $info = _install_get_version_info($version);
+        // Picking the first file does not necessarily result in the right file. So
+        // we check if at least the major version number is available.
+        if ($info['major']) {
+          $core = $info['major'] . '.x';
+          $data = [
+            'name' => 'drupal',
+            'project_type' => 'module',
+            'core' => $core,
+            'version' => $version,
+            'server_pattern' => $server_pattern,
+            'status' => 1,
+          ];
+          \Drupal::service('locale.project')->set($data['name'], $data);
+          module_load_include('compare.inc', 'locale');
+          // Reset project information static cache so that it uses the data
+          // set above.
+          locale_translation_clear_cache_projects();
+          locale_translation_check_projects_local(['drupal'], [$langcode]);
+        }
+      }
+    }
+  }
+}
+
+/**
+ * Finishes importing files at end of installation.
+ *
+ * If other projects besides Drupal core have been installed, their translation
+ * will be imported here.
+ *
+ * @param $install_state
+ *   An array of information about the current installation state.
+ *
+ * @return array
+ *   An array of batch definitions.
+ */
+function install_finish_translations(&$install_state) {
+  \Drupal::moduleHandler()->loadInclude('locale', 'fetch.inc');
+  \Drupal::moduleHandler()->loadInclude('locale', 'compare.inc');
+  \Drupal::moduleHandler()->loadInclude('locale', 'bulk.inc');
+
+  // Build a fresh list of installed projects. When more projects than core are
+  // installed, their translations will be downloaded (if required) and imported
+  // using a batch.
+  $projects = locale_translation_build_projects();
+  $languages = \Drupal::languageManager()->getLanguages();
+  $batches = [];
+  if (count($projects) > 1) {
+    $options = _locale_translation_default_update_options();
+    if ($batch = locale_translation_batch_update_build([], array_keys($languages), $options)) {
+      $batches[] = $batch;
+    }
+  }
+
+  // Creates configuration translations.
+  $batches[] = locale_config_batch_update_components([], array_keys($languages));
+  return $batches;
+}
+
+/**
+ * Performs final installation steps and displays a 'finished' page.
+ *
+ * @param $install_state
+ *   An array of information about the current installation state.
+ *
+ * @return
+ *   A message informing the user that the installation is complete.
+ */
+function install_finished(&$install_state) {
+  $profile = drupal_get_profile();
+
+  // Installation profiles are always loaded last.
+  module_set_weight($profile, 1000);
+
+  // Build the router once after installing all modules.
+  // This would normally happen upon KernelEvents::TERMINATE, but since the
+  // installer does not use an HttpKernel, that event is never triggered.
+  \Drupal::service('router.builder')->rebuild();
+
+  // Run cron to populate update status tables (if available) so that users
+  // will be warned if they've installed an out of date Drupal version.
+  // Will also trigger indexing of profile-supplied content or feeds.
+  \Drupal::service('cron')->run();
+
+  if ($install_state['interactive']) {
+    // Load current user and perform final login tasks.
+    // This has to be done after drupal_flush_all_caches()
+    // to avoid session regeneration.
+    $account = User::load(1);
+    user_login_finalize($account);
+  }
+
+  $success_message = t('Congratulations, you installed @drupal!', [
+    '@drupal' => drupal_install_profile_distribution_name(),
+  ]);
+  drupal_set_message($success_message);
+}
+
+/**
+ * Implements callback_batch_operation().
+ *
+ * Performs batch installation of modules.
+ */
+function _install_module_batch($module, $module_name, &$context) {
+  \Drupal::service('module_installer')->install([$module], FALSE);
+  $context['results'][] = $module;
+  $context['message'] = t('Installed %module module.', ['%module' => $module_name]);
+}
+
+/**
+ * Checks installation requirements and reports any errors.
+ *
+ * @param string $langcode
+ *   Language code to check for download.
+ * @param string $server_pattern
+ *   Server access pattern (to replace language code, version number, etc. in).
+ *
+ * @return array|null
+ *   Requirements compliance array. If the translation was downloaded
+ *   successfully then an empty array is returned. Otherwise the requirements
+ *   error with detailed information. NULL if the file already exists for this
+ *   language code.
+ */
+function install_check_translations($langcode, $server_pattern) {
+  $requirements = [];
+
+  $readable = FALSE;
+  $writable = FALSE;
+  // @todo: Make this configurable.
+  $site_path = \Drupal::service('site.path');
+  $files_directory = $site_path . '/files';
+  $translations_directory = $site_path . '/files/translations';
+  $translations_directory_exists = FALSE;
+  $online = FALSE;
+
+  // First attempt to create or make writable the files directory.
+  file_prepare_directory($files_directory, FILE_CREATE_DIRECTORY | FILE_MODIFY_PERMISSIONS);
+  // Then, attempt to create or make writable the translations directory.
+  file_prepare_directory($translations_directory, FILE_CREATE_DIRECTORY | FILE_MODIFY_PERMISSIONS);
+
+  // Get values so the requirements errors can be specific.
+  if (drupal_verify_install_file($translations_directory, FILE_EXIST, 'dir')) {
+    $readable = is_readable($translations_directory);
+    $writable = is_writable($translations_directory);
+    $translations_directory_exists = TRUE;
+  }
+
+  // The file already exists, no need to attempt to download.
+  if ($existing_file = glob($translations_directory . '/drupal-*.' . $langcode . '.po')) {
+    return;
+  }
+
+  $version = \Drupal::VERSION;
+  // For dev releases, remove the '-dev' part and trust the translation server
+  // to fall back to the latest stable release for that branch.
+  // @see locale_translation_build_projects()
+  if (preg_match("/^(\d+\.\d+\.).*-dev$/", $version, $matches)) {
+    // Example match: 8.0.0-dev => 8.0.x (Drupal core)
+    $version = $matches[1] . 'x';
+  }
+
+  // Build URL for the translation file and the translation server.
+  $variables = [
+    '%project' => 'drupal',
+    '%version' => $version,
+    '%core' => \Drupal::CORE_COMPATIBILITY,
+    '%language' => $langcode,
+  ];
+  $translation_url = strtr($server_pattern, $variables);
+
+  $elements = parse_url($translation_url);
+  $server_url = $elements['scheme'] . '://' . $elements['host'];
+
+  // Build the language name for display.
+  $languages = LanguageManager::getStandardLanguageList();
+  $language = isset($languages[$langcode]) ? $languages[$langcode][0] : $langcode;
+
+  // Check if any of the desired translation files are available or if the
+  // translation server can be reached. In other words, check if we are online
+  // and have an internet connection.
+  if ($translation_available = install_check_localization_server($translation_url)) {
+    $online = TRUE;
+  }
+  if (!$translation_available) {
+    if (install_check_localization_server($server_url)) {
+      $online = TRUE;
+    }
+  }
+
+  // If the translations directory does not exists, throw an error.
+  if (!$translations_directory_exists) {
+    $requirements['translations directory exists'] = [
+      'title'       => t('Translations directory'),
+      'value'       => t('The translations directory does not exist.'),
+      'severity'    => REQUIREMENT_ERROR,
+      'description' => t('The installer requires that you create a translations directory as part of the installation process. Create the directory %translations_directory . More details about installing Drupal are available in <a href=":install_txt">INSTALL.txt</a>.', ['%translations_directory' => $translations_directory, ':install_txt' => base_path() . 'core/INSTALL.txt']),
+    ];
+  }
+  else {
+    $requirements['translations directory exists'] = [
+      'title'       => t('Translations directory'),
+      'value'       => t('The directory %translations_directory exists.', ['%translations_directory' => $translations_directory]),
+    ];
+    // If the translations directory is not readable, throw an error.
+    if (!$readable) {
+      $requirements['translations directory readable'] = [
+        'title'       => t('Translations directory'),
+        'value'       => t('The translations directory is not readable.'),
+        'severity'    => REQUIREMENT_ERROR,
+        'description' => t('The installer requires read permissions to %translations_directory at all times. The <a href=":handbook_url">webhosting issues</a> documentation section offers help on this and other topics.', ['%translations_directory' => $translations_directory, ':handbook_url' => 'https://www.drupal.org/server-permissions']),
+      ];
+    }
+    // If translations directory is not writable, throw an error.
+    if (!$writable) {
+      $requirements['translations directory writable'] = [
+        'title'       => t('Translations directory'),
+        'value'       => t('The translations directory is not writable.'),
+        'severity'    => REQUIREMENT_ERROR,
+        'description' => t('The installer requires write permissions to %translations_directory during the installation process. The <a href=":handbook_url">webhosting issues</a> documentation section offers help on this and other topics.', ['%translations_directory' => $translations_directory, ':handbook_url' => 'https://www.drupal.org/server-permissions']),
+      ];
+    }
+    else {
+      $requirements['translations directory writable'] = [
+        'title'       => t('Translations directory'),
+        'value'       => t('The translations directory is writable.'),
+      ];
+    }
+  }
+
+  // If the translations server can not be contacted, throw an error.
+  if (!$online) {
+    $requirements['online'] = [
+      'title'       => t('Internet'),
+      'value'       => t('The translation server is offline.'),
+      'severity'    => REQUIREMENT_ERROR,
+      'description' => t('The installer requires to contact the translation server to download a translation file. Check your internet connection and verify that your website can reach the translation server at <a href=":server_url">@server_url</a>.', [':server_url' => $server_url, '@server_url' => $server_url]),
+    ];
+  }
+  else {
+    $requirements['online'] = [
+      'title'       => t('Internet'),
+      'value'       => t('The translation server is online.'),
+    ];
+    // If translation file is not found at the translation server, throw an
+    // error.
+    if (!$translation_available) {
+      $requirements['translation available'] = [
+        'title'       => t('Translation'),
+        'value'       => t('The %language translation is not available.', ['%language' => $language]),
+        'severity'    => REQUIREMENT_ERROR,
+        'description' => t('The %language translation file is not available at the translation server. <a href=":url">Choose a different language</a> or select English and translate your website later.', ['%language' => $language, ':url' => $_SERVER['SCRIPT_NAME']]),
+      ];
+    }
+    else {
+      $requirements['translation available'] = [
+        'title'       => t('Translation'),
+        'value'       => t('The %language translation is available.', ['%language' => $language]),
+      ];
+    }
+  }
+
+  if ($translations_directory_exists && $readable && $writable && $translation_available) {
+    $translation_downloaded = install_retrieve_file($translation_url, $translations_directory);
+
+    if (!$translation_downloaded) {
+      $requirements['translation downloaded'] = [
+        'title'       => t('Translation'),
+        'value'       => t('The %language translation could not be downloaded.', ['%language' => $language]),
+        'severity'    => REQUIREMENT_ERROR,
+        'description' => t('The %language translation file could not be downloaded. <a href=":url">Choose a different language</a> or select English and translate your website later.', ['%language' => $language, ':url' => $_SERVER['SCRIPT_NAME']]),
+      ];
+    }
+  }
+
+  return $requirements;
+}
+
+/**
+ * Checks installation requirements and reports any errors.
+ */
+function install_check_requirements($install_state) {
+  $profile = $install_state['parameters']['profile'];
+
+  // Check the profile requirements.
+  $requirements = drupal_check_profile($profile);
+
+  if ($install_state['settings_verified']) {
+    return $requirements;
+  }
+
+  // If Drupal is not set up already, we need to try to create the default
+  // settings and services files.
+  $default_files = [];
+  $default_files['settings.php'] = [
+    'file' => 'settings.php',
+    'file_default' => 'default.settings.php',
+    'title_default' => t('Default settings file'),
+    'description_default' => t('The default settings file does not exist.'),
+    'title' => t('Settings file'),
+  ];
+
+  foreach ($default_files as $default_file_info) {
+    $readable = FALSE;
+    $writable = FALSE;
+    $site_path = './' . \Drupal::service('site.path');
+    $file = $site_path . "/{$default_file_info['file']}";
+    $default_file = "./sites/default/{$default_file_info['file_default']}";
+    $exists = FALSE;
+    // Verify that the directory exists.
+    if (drupal_verify_install_file($site_path, FILE_EXIST, 'dir')) {
+      if (drupal_verify_install_file($file, FILE_EXIST)) {
+        // If it does, make sure it is writable.
+        $readable = drupal_verify_install_file($file, FILE_READABLE);
+        $writable = drupal_verify_install_file($file, FILE_WRITABLE);
+        $exists = TRUE;
+      }
+    }
+
+    // If the default $default_file does not exist, or is not readable,
+    // report an error.
+    if (!drupal_verify_install_file($default_file, FILE_EXIST | FILE_READABLE)) {
+      $requirements["default $file file exists"] = [
+        'title' => $default_file_info['title_default'],
+        'value' => $default_file_info['description_default'],
+        'severity' => REQUIREMENT_ERROR,
+        'description' => t('The @drupal installer requires that the %default-file file not be modified in any way from the original download.', [
+            '@drupal' => drupal_install_profile_distribution_name(),
+            '%default-file' => $default_file
+          ]),
+      ];
+    }
+    // Otherwise, if $file does not exist yet, we can try to copy
+    // $default_file to create it.
+    elseif (!$exists) {
+      $copied = drupal_verify_install_file($site_path, FILE_EXIST | FILE_WRITABLE, 'dir') && @copy($default_file, $file);
+      if ($copied) {
+        // If the new $file file has the same owner as $default_file this means
+        // $default_file is owned by the webserver user. This is an inherent
+        // security weakness because it allows a malicious webserver process to
+        // append arbitrary PHP code and then execute it. However, it is also a
+        // common configuration on shared hosting, and there is nothing Drupal
+        // can do to prevent it. In this situation, having $file also owned by
+        // the webserver does not introduce any additional security risk, so we
+        // keep the file in place. Additionally, this situation also occurs when
+        // the test runner is being run be different user than the webserver.
+        if (fileowner($default_file) === fileowner($file) || DRUPAL_TEST_IN_CHILD_SITE) {
+          $readable = drupal_verify_install_file($file, FILE_READABLE);
+          $writable = drupal_verify_install_file($file, FILE_WRITABLE);
+          $exists = TRUE;
+        }
+        // If $file and $default_file have different owners, this probably means
+        // the server is set up "securely" (with the webserver running as its
+        // own user, distinct from the user who owns all the Drupal PHP files),
+        // although with either a group or world writable sites directory.
+        // Keeping $file owned by the webserver would therefore introduce a
+        // security risk. It would also cause a usability problem, since site
+        // owners who do not have root access to the file system would be unable
+        // to edit their settings file later on. We therefore must delete the
+        // file we just created and force the administrator to log on to the
+        // server and create it manually.
+        else {
+          $deleted = @drupal_unlink($file);
+          // We expect deleting the file to be successful (since we just
+          // created it ourselves above), but if it fails somehow, we set a
+          // variable so we can display a one-time error message to the
+          // administrator at the bottom of the requirements list. We also try
+          // to make the file writable, to eliminate any conflicting error
+          // messages in the requirements list.
+          $exists = !$deleted;
+          if ($exists) {
+            $settings_file_ownership_error = TRUE;
+            $readable = drupal_verify_install_file($file, FILE_READABLE);
+            $writable = drupal_verify_install_file($file, FILE_WRITABLE);
+          }
+        }
+      }
+    }
+
+    // If the $file does not exist, throw an error.
+    if (!$exists) {
+      $requirements["$file file exists"] = [
+        'title' => $default_file_info['title'],
+        'value' => t('The %file does not exist.', ['%file' => $default_file_info['title']]),
+        'severity' => REQUIREMENT_ERROR,
+        'description' => t('The @drupal installer requires that you create a %file as part of the installation process. Copy the %default_file file to %file. More details about installing Drupal are available in <a href=":install_txt">INSTALL.txt</a>.', [
+            '@drupal' => drupal_install_profile_distribution_name(),
+            '%file' => $file,
+            '%default_file' => $default_file,
+            ':install_txt' => base_path() . 'core/INSTALL.txt'
+          ]),
+      ];
+    }
+    else {
+      $requirements["$file file exists"] = [
+        'title' => $default_file_info['title'],
+        'value' => t('The %file exists.', ['%file' => $file]),
+      ];
+      // If the $file is not readable, throw an error.
+      if (!$readable) {
+        $requirements["$file file readable"] = [
+          'title' => $default_file_info['title'],
+          'value' => t('The %file is not readable.', ['%file' => $default_file_info['title']]),
+          'severity' => REQUIREMENT_ERROR,
+          'description' => t('@drupal requires read permissions to %file at all times. The <a href=":handbook_url">webhosting issues</a> documentation section offers help on this and other topics.', [
+              '@drupal' => drupal_install_profile_distribution_name(),
+              '%file' => $file,
+              ':handbook_url' => 'https://www.drupal.org/server-permissions'
+            ]),
+        ];
+      }
+      // If the $file is not writable, throw an error.
+      if (!$writable) {
+        $requirements["$file file writeable"] = [
+          'title' => $default_file_info['title'],
+          'value' => t('The %file is not writable.', ['%file' => $default_file_info['title']]),
+          'severity' => REQUIREMENT_ERROR,
+          'description' => t('The @drupal installer requires write permissions to %file during the installation process. The <a href=":handbook_url">webhosting issues</a> documentation section offers help on this and other topics.', [
+              '@drupal' => drupal_install_profile_distribution_name(),
+              '%file' => $file,
+              ':handbook_url' => 'https://www.drupal.org/server-permissions'
+            ]),
+        ];
+      }
+      else {
+        $requirements["$file file"] = [
+          'title' => $default_file_info['title'],
+          'value' => t('The @file is writable.', ['@file' => $default_file_info['title']]),
+        ];
+      }
+      if (!empty($settings_file_ownership_error)) {
+        $requirements["$file file ownership"] = [
+          'title' => $default_file_info['title'],
+          'value' => t('The @file is owned by the web server.', ['@file' => $default_file_info['title']]),
+          'severity' => REQUIREMENT_ERROR,
+          'description' => t('The @drupal installer failed to create a %file file with proper file ownership. Log on to your web server, remove the existing %file file, and create a new one by copying the %default_file file to %file. More details about installing Drupal are available in <a href=":install_txt">INSTALL.txt</a>. The <a href=":handbook_url">webhosting issues</a> documentation section offers help on this and other topics.', [
+              '@drupal' => drupal_install_profile_distribution_name(),
+              '%file' => $file,
+              '%default_file' => $default_file,
+              ':install_txt' => base_path() . 'core/INSTALL.txt',
+              ':handbook_url' => 'https://www.drupal.org/server-permissions'
+            ]),
+        ];
+      }
+    }
+  }
+  return $requirements;
+}
+
+/**
+ * Displays installation requirements.
+ *
+ * @param array $install_state
+ *   An array of information about the current installation state.
+ * @param array $requirements
+ *   An array of requirements, in the same format as is returned by
+ *   hook_requirements().
+ *
+ * @return
+ *   A themed status report, or an exception if there are requirement errors.
+ *   If there are only requirement warnings, a themed status report is shown
+ *   initially, but the user is allowed to bypass it by providing 'continue=1'
+ *   in the URL. Otherwise, no output is returned, so that the next task can be
+ *   run in the same page request.
+ *
+ * @throws \Drupal\Core\Installer\Exception\InstallerException
+ */
+function install_display_requirements($install_state, $requirements) {
+  // Check the severity of the requirements reported.
+  $severity = drupal_requirements_severity($requirements);
+
+  // If there are errors, always display them. If there are only warnings, skip
+  // them if the user has provided a URL parameter acknowledging the warnings
+  // and indicating a desire to continue anyway. See drupal_requirements_url().
+  if ($severity == REQUIREMENT_ERROR || ($severity == REQUIREMENT_WARNING && empty($install_state['parameters']['continue']))) {
+    if ($install_state['interactive']) {
+      $build['report']['#type'] = 'status_report';
+      $build['report']['#requirements'] = $requirements;
+      if ($severity == REQUIREMENT_WARNING) {
+        $build['#title'] = t('Requirements review');
+        $build['#suffix'] = t('Check the messages and <a href=":retry">retry</a>, or you may choose to <a href=":cont">continue anyway</a>.', [':retry' => drupal_requirements_url(REQUIREMENT_ERROR), ':cont' => drupal_requirements_url($severity)]);
+      }
+      else {
+        $build['#title'] = t('Requirements problem');
+        $build['#suffix'] = t('Check the messages and <a href=":url">try again</a>.', [':url' => drupal_requirements_url($severity)]);
+      }
+      return $build;
+    }
+    else {
+      // Throw an exception showing any unmet requirements.
+      $failures = [];
+      foreach ($requirements as $requirement) {
+        // Skip warnings altogether for non-interactive installations; these
+        // proceed in a single request so there is no good opportunity (and no
+        // good method) to warn the user anyway.
+        if (isset($requirement['severity']) && $requirement['severity'] == REQUIREMENT_ERROR) {
+          $failures[] = $requirement['title'] . ': ' . $requirement['value'] . "\n\n" . $requirement['description'];
+        }
+      }
+      if (!empty($failures)) {
+        throw new InstallerException(implode("\n\n", $failures));
+      }
+    }
+  }
+}
+
+/**
+ * Installation task; writes profile to settings.php if possible.
+ *
+ * @param array $install_state
+ *   An array of information about the current installation state.
+ *
+ * @see _install_select_profile()
+ *
+ * @throws \Drupal\Core\Installer\Exception\InstallProfileMismatchException
+ *
+ * @deprecated in Drupal 8.3.0 and will be removed before Drupal 9.0.0. The
+ *    install profile is written to core.extension.
+ */
+function install_write_profile($install_state) {
+  // Only need to write to settings.php if it is possible. The primary storage
+  // for the install profile is the core.extension configuration.
+  $settings_path = \Drupal::service('site.path') . '/settings.php';
+  if (is_writable($settings_path)) {
+    // Remember the profile which was used.
+    $settings['settings']['install_profile'] = (object) [
+      'value' => $install_state['parameters']['profile'],
+      'required' => TRUE,
+    ];
+    drupal_rewrite_settings($settings);
+  }
+  elseif (($settings_profile = Settings::get('install_profile')) && $settings_profile !== $install_state['parameters']['profile']) {
+    throw new InstallProfileMismatchException($install_state['parameters']['profile'], $settings_profile, $settings_path, \Drupal::translation());
+  }
+}