install.core.inc

<?php

/**
 * @file
 * API functions for installing Drupal.
 */

use Drupal\Component\Utility\UrlHelper;
use Drupal\Core\Batch\BatchBuilder;
use Drupal\Core\Config\ConfigImporter;
use Drupal\Core\Config\ConfigImporterException;
use Drupal\Core\Config\Importer\ConfigImporterBatch;
use Drupal\Core\Config\FileStorage;
use Drupal\Core\Config\StorageComparer;
use Drupal\Core\DrupalKernel;
use Drupal\Core\Database\Database;
use Drupal\Core\Database\DatabaseExceptionWrapper;
use Drupal\Core\File\FileSystemInterface;
use Drupal\Core\Form\FormState;
use Drupal\Core\Installer\Exception\AlreadyInstalledException;
use Drupal\Core\Installer\Exception\InstallerException;
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\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.
 * @param callable $callback
 *   (optional) A callback to allow command line processes to update a progress
 *   bar. The callback is passed the $install_state variable.
 *
 * @see install_state_defaults()
 */
function install_drupal($class_loader, $settings = [], callable $callback = NULL) {
  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, $callback);
  }
  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($GLOBALS['install_state']);
    // If installation is finished ensure any further container rebuilds do not
    // use the installer's service provider.
    unset($GLOBALS['conf']['container_service_providers']['InstallerServiceProvider']);
  }

  // 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 ($state['interactive']) {
    // If a session has been initiated in this request, make sure to save it.
    if (\Drupal::request()->hasSession()) {
      \Drupal::request()->getSession()->save();
    }
    if ($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.
      $finish_url = '';
      if (isset($install_state['profile_info']['distribution']['install']['finish_url'])) {
        $finish_url = $install_state['profile_info']['distribution']['install']['finish_url'];
      }
      install_goto($finish_url);
    }
  }
}

/**
 * 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,
    // Partial configuration cached during an installation from existing config.
    'config' => NULL,
    // The path to the configuration to install when installing from config.
    'config_install_path' => 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 $install_state
 *   An array of information about the current installation state. This is
 *   modified with information gleaned from the beginning of the page request.
 *
 * @see install_drupal()
 */
function install_begin_request($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';

  // 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');
  }

  $site_path = empty($install_state['site_path']) ? DrupalKernel::findSitePath($request, FALSE) : $install_state['site_path'];
  Settings::initialize(dirname(__DIR__, 2), $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__ . '/form.inc';
  require_once __DIR__ . '/batch.inc';

  // Load module basics (needed for hook invokes).
  include_once __DIR__ . '/module.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'));

  // Register the class loader so contrib and custom database drivers can be
  // autoloaded.
  // @see drupal_get_database_types()
  $container->set('class_loader', $class_loader);

  \Drupal::setContainer($container);

  // Determine whether base system services are ready to operate.
  try {
    $sync_directory = Settings::get('config_sync_directory', FALSE);
    $install_state['config_verified'] = file_exists($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 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']['InstallerServiceProvider'] = 'Drupal\Core\Installer\NormalInstallerServiceProvider';
  }
  $GLOBALS['conf']['container_service_providers']['InstallerConfigOverride'] = 'Drupal\Core\Installer\ConfigOverride';

  // Note, InstallerKernel::createFromRequest() is not used because Settings is
  // already initialized.
  $kernel = new InstallerKernel($environment, $class_loader, FALSE);
  $kernel::bootEnvironment();
  $kernel->setSitePath($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';
  }
  /** @var \Drupal\Core\File\FileSystemInterface $file_system */
  $file_system = $container->get('file_system');
  $container->set('string_translator.file_translation', new FileTranslation($directory, $file_system));
  $container->get('string_translation')
    ->addTranslator($container->get('string_translator.file_translation'));

  // Add list of all available profiles to the installation state.
  $listing = new ExtensionDiscovery($container->getParameter('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());
    // drupal_get_filename() is called both with 'module' and 'profile', see
    // \Drupal\Core\Config\ConfigInstaller::getProfileStorages for example.
    drupal_get_filename('module', $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'];
    }
  }

  // Before having installed the system module and being able to do a module
  // rebuild, prime the drupal_get_filename() static cache with the system
  // module's location.
  // @todo Remove as part of https://www.drupal.org/node/2186491
  drupal_get_filename('module', 'system', 'core/modules/system/system.info.yml');

  // Use the language from profile configuration if available.
  if (!empty($install_state['config_install_path']) && $install_state['config']['system.site']) {
    $install_state['parameters']['langcode'] = $install_state['config']['system.site']['default_langcode'];
  }
  elseif (isset($install_state['profile_info']['distribution']['langcode'])) {
    // Otherwise, Use the language from the profile configuration, if available,
    // to override the language previously set in the parameters.
    $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.
 * @param callable $callback
 *   (optional) A callback to allow command line processes to update a progress
 *   bar. The callback is passed the $install_state variable.
 *
 * @return
 *   HTML output from the last completed task.
 */
function install_run_tasks(&$install_state, callable $callback = NULL) {
  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' : $task_name);
      }
    }
    if ($callback) {
      $callback($install_state);
    }
    // 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 (\Drupal::request()->hasSession()) {
          \Drupal::request()->getSession()->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.
  $locale_module_installed = \Drupal::moduleHandler()->moduleExists('locale');
  $needs_translations = $locale_module_installed && ((count($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_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',
    ],
  ];

  if (!empty($install_state['config_install_path'])) {
    // The chosen profile indicates that rather than installing a new site, an
    // instance of the same site should be installed from the given
    // configuration.
    // That means we need to remove the steps installing the extensions and
    // replace them with a configuration synchronization step.
    unset($tasks['install_download_translation']);
    $key = array_search('install_profile_modules', array_keys($tasks), TRUE);
    unset($tasks['install_profile_modules']);
    unset($tasks['install_profile_themes']);
    unset($tasks['install_install_profile']);
    $config_tasks = [
      'install_config_import_batch' => [
        'display_name' => t('Install configuration'),
        'type' => 'batch',
      ],
      'install_config_download_translations' => [],
      'install_config_revert_install_changes' => [],
    ];
    $tasks = array_slice($tasks, 0, $key, TRUE) +
      $config_tasks +
      array_slice($tasks, $key, NULL, TRUE);
  }

  // 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;
}