install.core.inc

<?php

use Drupal\Component\Utility\Crypt;

use Drupal\Core\Config\FileStorage;
use Drupal\Core\DrupalKernel;
use Drupal\Core\CoreServiceProvider;
use Drupal\Core\Database\Database;
use Drupal\Core\Database\Install\TaskException;
use Drupal\Core\Language\Language;
use Drupal\Core\Language\LanguageManager;
use Drupal\Core\StringTranslation\Translator\FileTranslation;

use Drupal\Core\DependencyInjection\ContainerBuilder;
use Symfony\Component\DependencyInjection\Reference;
use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\HttpFoundation\Response;

use Guzzle\Http\Exception\RequestException;

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

/**
 * 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 $settings
 *   An optional array of installation settings. Leave this empty for a normal,
 *   interactive, browser-based installation intended to occur over multiple
 *   page requests. Alternatively, if an array of settings is passed in, the
 *   installer will attempt to use it to perform the installation in a single
 *   page request (optimized for the command line) and not send any output
 *   intended for the web browser. See install_state_defaults() for a list of
 *   elements that are allowed to appear in this array.
 *
 * @see install_state_defaults()
 */
function install_drupal($settings = array()) {
  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 + array('interactive' => $interactive) + install_state_defaults();
  try {
    // Begin the page request. This adds information about the current state of
    // the Drupal installation to the passed-in array.
    install_begin_request($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 (Exception $e) {
    // When an installation error occurs, either send the error to the web
    // browser or pass on the exception so the calling script can use it.
    if ($install_state['interactive']) {
      install_display_output($e->getMessage(), $install_state);
    }
    else {
      throw $e;
    }
  }
  // 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 ($state['interactive']) {
    if ($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);
    }
  }
}

/**
 * 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['values']
 * array that is passed on to the form submission via drupal_form_submit()).
 *
 * @see drupal_form_submit()
 */
function install_state_defaults() {
  $defaults = array(
    // The current task being processed.
    'active_task' => NULL,
    // The last task that was completed during the previous installation
    // request.
    'completed_task' => NULL,
    // This becomes TRUE only when a valid config directory is created or
    // detected.
    'config_verified' => FALSE,
    // This becomes TRUE only when Drupal's system module is installed.
    'database_tables_exist' => FALSE,
    // This becomes TRUE only when a valid database connection can be
    // established.
    'database_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['values'] array that is passed on to the form
    // submission via drupal_form_submit().
    'forms' => array(),
    // 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' => array(),
    // 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' => array(),
    // An array of available installation profiles.
    'profiles' => array(),
    // An array of server variables that will be substituted into the global
    // $_SERVER array via drupal_override_server_variables(). Used by
    // non-interactive installations only.
    'server' => array(),
    // 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',
    // This becomes TRUE only when a valid settings.php file is written
    // (containing both valid database connection information and a valid
    // config directory).
    'settings_verified' => FALSE,
    // 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' => array(),
    // An array of translation files URIs available for the installation. Keyed
    // by the translation language code.
    'translations' => array(),
  );
  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 $install_state
 *   An array of information about the current installation state. This is
 *   modified with information gleaned from the beginning of the page request.
 */
function install_begin_request(&$install_state) {
  // Add any installation parameters passed in via the URL.
  if ($install_state['interactive']) {
    $install_state['parameters'] += $_GET;
  }

  // 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 (!$install_state['interactive']) {
    drupal_override_server_variables($install_state['server']);
  }

  // Initialize conf_path().
  // This primes the site path to be used during installation. By not requiring
  // settings.php, a bare site folder can be prepared in the /sites directory,
  // which will be used for installing Drupal.
  conf_path(FALSE);

  drupal_bootstrap(DRUPAL_BOOTSTRAP_CONFIGURATION);

  // 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. To
  // avoid this yet allow for automated testing of the installer, make sure
  // there is also a special test-specific settings.php overriding conf_path().
  // _drupal_load_test_overrides() sets the simpletest_conf_path in-memory
  // setting in this case.
  if ($install_state['interactive'] && drupal_valid_test_ua() && !settings()->get('simpletest_conf_path')) {
    header($_SERVER['SERVER_PROTOCOL'] . ' 403 Forbidden');
    exit;
  }

  // A request object from the HTTPFoundation to tell us about the request.
  $request = Request::createFromGlobals();

  // This must go after drupal_bootstrap(), which unsets globals!
  global $conf;

  // If we have a language selected and it is not yet saved in the system
  // (eg. pre-database data screens we are unable to persistently store
  // the default language), we should set language_default so the proper
  // language is used to display installer pages as early as possible.
  // The language list is stored in configuration and cannot be saved either
  // until later in the process. Language negotiation bootstrapping needs
  // the new default language to be in the list though, so inject it in.
  if (!empty($install_state['parameters']['langcode']) && language_default()->id != $install_state['parameters']['langcode']) {
    $GLOBALS['conf']['language_default'] = array('id' => $install_state['parameters']['langcode']);

    $languages = &drupal_static('language_list');
    $languages[$install_state['parameters']['langcode']] = new Language($GLOBALS['conf']['language_default']);
  }

  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__ . '/../../' . settings()->get('path_inc', 'core/includes/path.inc');

  // Load module basics (needed for hook invokes).
  include_once __DIR__ . '/module.inc';
  include_once __DIR__ . '/session.inc';
  require_once __DIR__ . '/entity.inc';

  // Determine whether the configuration system is ready to operate.
  $install_state['config_verified'] = install_verify_config_directory(CONFIG_ACTIVE_DIRECTORY) && install_verify_config_directory(CONFIG_STAGING_DIRECTORY);

  // Create a minimal container for t() to work.
  // This container will be overriden but it needed for the very early
  // installation process when database tasks run.
  $container = new ContainerBuilder();
  // Register the translation services.
  install_register_translation_service($container);
  Drupal::setContainer($container);

  // Check existing settings.php.
  $install_state['database_verified'] = install_verify_database_settings();
  $install_state['settings_verified'] = $install_state['config_verified'] && $install_state['database_verified'];

  // If it is not, replace the configuration storage with the InstallStorage
  // implementation, for the following reasons:
  // - The first call into drupal_container() will try to set up the regular
  //   runtime configuration storage, using the CachedStorage by default. It
  //   calls config_get_config_directory() to retrieve the config directory to
  //   use, but that throws an exception, since $config_directories is not
  //   defined since there is no settings.php yet. If there is a prepared
  //   settings.php already, then the returned directory still cannot be used,
  //   because it does not necessarily exist. The installer ensures that it
  //   exists and is writeable in a later step.
  // - The installer outputs maintenance theme pages and performs many other
  //   operations, which try to load configuration. Since there is no active
  //   configuration yet, and because the configuration system does not have a
  //   notion of default values at runtime, data is missing in many places. The
  //   lack of data does not trigger errors, but results in a broken user
  //   interface (e.g., missing page title, etc).
  // - The actual configuration data to read during installation is essentially
  //   the default configuration provided by the installation profile and
  //   modules (most notably System module). The InstallStorage therefore reads
  //   from the default configuration directories of extensions.
  // This override is reverted as soon as the config directory and the
  // database has been set up successfully.
  // @see drupal_install_config_directories()
  // @see install_settings_form_submit()
  if ($install_state['settings_verified']) {
    $kernel = new DrupalKernel('install', drupal_classloader(), FALSE);
    $kernel->boot();
    $container = $kernel->getContainer();
    // Add the file translation service to the container.
    $container->set('string_translator.file_translation', install_file_translation_service());
    $container->get('string_translation')->addTranslator($container->get('string_translator.file_translation'));
    // Set the request in the kernel to the new created Request above
    // so it is available to the rest of the installation process.
    $container->set('request', $request);
  }
  else {
    // @todo Move into a proper Drupal\Core\DependencyInjection\InstallContainerBuilder.
    $container = new ContainerBuilder();

    $container->register('event_dispatcher', 'Symfony\Component\EventDispatcher\EventDispatcher');

    $container->register('config.storage', 'Drupal\Core\Config\InstallStorage');
    $container->register('config.context.factory', 'Drupal\Core\Config\Context\ConfigContextFactory')
      ->addArgument(new Reference('event_dispatcher'));

    $container->register('config.context', 'Drupal\Core\Config\Context\ContextInterface')
      ->setFactoryService(new Reference('config.context.factory'))
      ->setFactoryMethod('get');

    $container->register('config.factory', 'Drupal\Core\Config\ConfigFactory')
      ->addArgument(new Reference('config.storage'))
      ->addArgument(new Reference('config.context'));

    // Register the 'language_manager' service.
    $container->register('language_manager', 'Drupal\Core\Language\LanguageManager');

    // Register the translation services.
    install_register_translation_service($container);

    foreach (array('bootstrap', 'config', 'cache', 'menu', 'page', 'path') as $bin) {
      $container
        ->register("cache.$bin", 'Drupal\Core\Cache\MemoryBackend')
        ->addArgument($bin);
    }

    // The install process cannot use the database lock backend since the database
    // is not fully up, so we use a null backend implementation during the
    // installation process. This will also speed up the installation process.
    // The site being installed will use the real lock backend when doing AJAX
    // requests but, except for a WSOD, there is no chance for a a lock to stall
    // (as opposed to the cache backend) so we can afford having a null
    // implementation here.
    $container->register('lock', 'Drupal\Core\Lock\NullLockBackend');

    // Register a module handler for managing enabled modules.
    $container
      ->register('module_handler', 'Drupal\Core\Extension\ModuleHandler');

    // Register the Guzzle HTTP client for fetching translation files from a
    // remote translation server such as localization.drupal.org.
    $container->register('http_default_client', 'Guzzle\Http\Client')
      ->addArgument(NULL)
      ->addArgument(array(
        'curl.CURLOPT_TIMEOUT' => 30.0,
        'curl.CURLOPT_MAXREDIRS' => 3,
      ))
      ->addMethodCall('setUserAgent', array('Drupal (+http://drupal.org/)'));

    // Register the expirable key value store used by form cache.
    $container
      ->register('keyvalue.expirable', 'Drupal\Core\KeyValueStore\KeyValueExpirableFactory')
      ->addArgument(new Reference('service_container'));
    $container
      ->register('keyvalue.expirable.null', 'Drupal\Core\KeyValueStore\KeyValueNullExpirableFactory');
    $conf['keyvalue_expirable_default'] = 'keyvalue.expirable.null';

    // Register Twig template engine for use during install.
    CoreServiceProvider::registerTwig($container);

    $container->register('url_generator', 'Drupal\Core\Routing\NullGenerator');

    Drupal::setContainer($container);
  }

  // Set up $language, so t() caller functions will still work.
  drupal_language_initialize();
  // Add in installation language if present.
  if (isset($install_state['parameters']['langcode'])) {
    Drupal::translation()->setDefaultLangcode($install_state['parameters']['langcode']);
  }

  require_once __DIR__ . '/ajax.inc';

  $module_handler = Drupal::moduleHandler();
  if (!$module_handler->moduleExists('system')) {
    // Override the module list with a minimal set of modules.
    $module_handler->setModuleList(array('system' => 'core/modules/system/system.module'));
  }
  $module_handler->load('system');

  require_once __DIR__ . '/cache.inc';

  // 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']) {
    // Initialize the database system. Note that the connection
    // won't be initialized until it is actually requested.
    require_once __DIR__ . '/database.inc';

    // 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 (!empty($GLOBALS['databases'])) {
      throw new Exception(install_already_done_error());
    }
  }

  // Ensure that the active configuration directory is empty before installation
  // starts.
  if ($install_state['config_verified'] && empty($task)) {
    $config = glob(config_get_config_directory(CONFIG_ACTIVE_DIRECTORY) . '/*.' . FileStorage::getFileExtension());
    if (!empty($config)) {
      $task = NULL;
      throw new Exception(install_already_done_error());
    }
  }

  // Modify the installation state as appropriate.
  $install_state['completed_task'] = $task;
  $install_state['database_tables_exist'] = !empty($task);

  // Add the list of available profiles to the installation state.
  $install_state['profiles'] += drupal_system_listing('/^' . DRUPAL_PHP_FUNCTION_PATTERN . '\.profile$/', 'profiles');
}

/**
 * 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);
    $install_state['parameters_changed'] = ($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 ($install_state['database_tables_exist'] && ($task['run'] == INSTALL_TASK_RUN_IF_NOT_COMPLETED || $install_state['installation_finished'])) {
        variable_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.
 * @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 ($task['type'] == 'form') {
    require_once __DIR__ . '/form.inc';
    if ($install_state['interactive']) {
      // For interactive forms, build the form and ensure that it will not
      // redirect, since the installer handles its own redirection only after
      // marking the form submission task complete.
      $form_state = array(
        // We need to pass $install_state by reference in order for forms to
        // modify it, since the form API will use it in call_user_func_array(),
        // which requires that referenced variables be passed explicitly.
        'build_info' => array('args' => array(&$install_state)),
        'no_redirect' => TRUE,
      );
      $form = drupal_build_form($function, $form_state);
      // If a successful form submission did not occur, the form needs to be
      // rendered, which means the task is not complete yet.
      if (empty($form_state['executed'])) {
        $install_state['task_not_complete'] = TRUE;
        return drupal_render($form);
      }
      // Otherwise, return nothing so the next task will run in the same
      // request.
      return;
    }
    else {
      // For non-interactive forms, submit the form programmatically with the
      // values taken from the installation state. Throw an exception if any
      // errors were encountered.
      $form_state = array(
        'values' => !empty($install_state['forms'][$function]) ? $install_state['forms'][$function] : array(),
        // We need to pass $install_state by reference in order for forms to
        // modify it, since the form API will use it in call_user_func_array(),
        // which requires that referenced variables be passed explicitly.
        'build_info' => array('args' => array(&$install_state)),
      );
      drupal_form_submit($function, $form_state);
      $errors = form_get_errors();
      if (!empty($errors)) {
        throw new Exception(implode("\n", $errors));
      }
    }
  }

  elseif ($task['type'] == 'batch') {
    // Start a new batch based on the task function, if one is not running
    // already.
    $current_batch = variable_get('install_current_batch');
    if (!$install_state['interactive'] || !$current_batch) {
      $batch = $function($install_state);
      if (empty($batch)) {
        // If the task did some processing and decided no batch was necessary,
        // there is nothing more to do here.
        return;
      }
      batch_set($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']) {
        variable_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.
      $response = batch_process(install_redirect_url($install_state), install_full_redirect_url($install_state));
      if ($response instanceof Response) {
        // Save $_SESSION data from batch.
        drupal_session_commit();
        // 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) {
      include_once __DIR__ . '/batch.inc';
      $output = _batch_page();
      // Because Batch API now returns a JSON response for intermediary steps,
      // but the installer doesn't handle Response objects yet, just send the
      // output here and emulate the old model.
      // @todo Replace this when we refactor the installer to use a request-
      //   response workflow.
      if ($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.
        variable_del('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).
 *
 * @param $install_state
 *   An array of information about the current installation state.
 *
 * @return
 *   A list of tasks, with associated metadata.
 */
function install_tasks($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.
  $needs_translations = count($install_state['translations']) > 1 && !empty($install_state['parameters']['langcode']) && $install_state['parameters']['langcode'] != 'en';
  // 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 = array(
    'install_select_language' => array(
      'display_name' => t('Choose language'),
      'run' => INSTALL_TASK_RUN_IF_REACHED,
    ),
    'install_download_translation' => array(
      'run' => $needs_download ? INSTALL_TASK_RUN_IF_REACHED : INSTALL_TASK_SKIP,
    ),
    'install_select_profile' => array(
      'display_name' => t('Choose profile'),
      'display' => count($install_state['profiles']) != 1,
      'run' => INSTALL_TASK_RUN_IF_REACHED,
    ),
    'install_load_profile' => array(
      'run' => INSTALL_TASK_RUN_IF_REACHED,
    ),
    'install_verify_requirements' => array(
      'display_name' => t('Verify requirements'),
    ),
    'install_settings_form' => array(
      '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' => $install_state['settings_verified'] ? INSTALL_TASK_SKIP : INSTALL_TASK_RUN_IF_NOT_COMPLETED,
    ),
    'install_base_system' => array(
    ),
    'install_bootstrap_full' => array(
      'run' => INSTALL_TASK_RUN_IF_REACHED,
    ),
    'install_profile_modules' => array(
      'display_name' => count($install_state['profiles']) == 1 ? t('Install site') : t('Installation profile'),
      'type' => 'batch',
    ),
    'install_import_translations' => array(
      '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' => array(
      'display_name' => t('Configure site'),
      'type' => 'form',
    ),
  );

  // 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'];
    $profile_install_file = dirname($install_state['profiles'][$profile]->uri) . '/' . $profile . '.install';
    if (file_exists($profile_install_file)) {
      include_once $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 += array(
    'install_import_translations_remaining' => array(
      'display_name' => t('Finish translations'),
      'display' => $needs_translations,
      'type' => 'batch',
      'run' => $needs_translations ? INSTALL_TASK_RUN_IF_NOT_COMPLETED : INSTALL_TASK_SKIP,
    ),
    'install_update_configuration_translations' => array(
      'display_name' => t('Translate configuration'),
      'display' => $needs_translations,
      'type' => 'batch',
      'run' => $needs_translations ? INSTALL_TASK_RUN_IF_NOT_COMPLETED : INSTALL_TASK_SKIP,
    ),
    'install_finished' => array(
      'display_name' => t('Finished'),
    ),
  );

  // Allow the installation profile to modify the full list of tasks.
  if (!empty($install_state['parameters']['profile'])) {
    $profile = $install_state['parameters']['profile'];
    $profile_file = $install_state['profiles'][$profile]->uri;
    if (file_exists($profile_file)) {
      include_once $profile_file;
      $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) {
    $task += array(
      'display_name' => NULL,
      'display' => !empty($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
 * theme_task_list().
 *
 * @param $install_state
 *   An array of information about the current installation state.
 *
 * @return
 *   A list of tasks, with keys equal to the machine-readable task name and
 *   values equal to the name that should be displayed.
 *
 * @see theme_task_list()
 */
function install_tasks_to_display($install_state) {
  $displayed_tasks = array();
  foreach (install_tasks($install_state) as $name => $task) {
    if ($task['display']) {
      $displayed_tasks[$name] = $task['display_name'];
    }
  }
  return $displayed_tasks;
}

/**
 * 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?' . drupal_http_build_query($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 drupal_set_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) {
  drupal_page_header();

  // 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.
  $noindex_meta_tag = array(
    '#tag' => 'meta',
    '#attributes' => array(
      'name' => 'robots',
      'content' => 'noindex, nofollow',
    ),
  );
  drupal_add_html_head($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.
  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 : $install_state['active_task'];
    drupal_add_region_content('sidebar_first', theme('task_list', array('items' => install_tasks_to_display($install_state), 'active' => $active_task, 'variant' => 'install')));
  }
  print theme('install_page', array('content' => $output));
  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();

  // 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();

  // Enable the user module so that sessions can be recorded during the
  // upcoming bootstrap step.
  module_enable(array('user'), FALSE);

  // Save the list of other modules to install for the upcoming tasks.
  // variable_set() can be used now that system.module is installed.
  $modules = $install_state['profile_info']['dependencies'];

  // The installation profile is also a module, which needs to be installed
  // after all the dependencies have been installed.
  $modules[] = drupal_get_profile();