DbUpdateController::selection

protected DbUpdateController::selection(Request $request)

protected function selection(Request $request) {
  // Make sure there is no stale theme registry.
  $this->cache->deleteAll();

  $count = 0;
  $incompatible_count = 0;
  $build['start'] = array(
    '#tree' => TRUE,
    '#type' => 'details',
  );

  // Ensure system.module's updates appear first.
  $build['start']['system'] = array();

  $starting_updates = array();
  $incompatible_updates_exist = FALSE;
  $updates_per_module = [];
  foreach (['update', 'post_update'] as $update_type) {
    switch ($update_type) {
      case 'update':
        $updates = update_get_update_list();
        break;
      case 'post_update':
        $updates = $this->postUpdateRegistry->getPendingUpdateInformation();
        break;
    }
    foreach ($updates as $module => $update) {
      if (!isset($update['start'])) {
        $build['start'][$module] = array(
          '#type' => 'item',
          '#title' => $module . ' module',
          '#markup' => $update['warning'],
          '#prefix' => '<div class="messages messages--warning">',
          '#suffix' => '</div>',
        );
        $incompatible_updates_exist = TRUE;
        continue;
      }
      if (!empty($update['pending'])) {
        $updates_per_module += [$module => []];
        $updates_per_module[$module] = array_merge($updates_per_module[$module], $update['pending']);
        $build['start'][$module] = array(
          '#type' => 'hidden',
          '#value' => $update['start'],
        );
        // Store the previous items in order to merge normal updates and
        // post_update functions together.
        $build['start'][$module] = array(
          '#theme' => 'item_list',
          '#items' => $updates_per_module[$module],
          '#title' => $module . ' module',
        );

        if ($update_type === 'update') {
          $starting_updates[$module] = $update['start'];
        }
      }
      if (isset($update['pending'])) {
        $count = $count + count($update['pending']);
      }
    }
  }

  // Find and label any incompatible updates.
  foreach (update_resolve_dependencies($starting_updates) as $data) {
    if (!$data['allowed']) {
      $incompatible_updates_exist = TRUE;
      $incompatible_count++;
      $module_update_key = $data['module'] . '_updates';
      if (isset($build['start'][$module_update_key]['#items'][$data['number']])) {
        if ($data['missing_dependencies']) {
          $text = $this->t('This update will been skipped due to the following missing dependencies:') . '<em>' . implode(', ', $data['missing_dependencies']) . '</em>';
        }
        else {
          $text = $this->t("This update will be skipped due to an error in the module's code.");
        }
        $build['start'][$module_update_key]['#items'][$data['number']] .= '<div class="warning">' . $text . '</div>';
      }
      // Move the module containing this update to the top of the list.
      $build['start'] = array($module_update_key => $build['start'][$module_update_key]) + $build['start'];
    }
  }

  // Warn the user if any updates were incompatible.
  if ($incompatible_updates_exist) {
    drupal_set_message($this->t('Some of the pending updates cannot be applied because their dependencies were not met.'), 'warning');
  }

  if (empty($count)) {
    drupal_set_message($this->t('No pending updates.'));
    unset($build);
    $build['links'] = array(
      '#theme' => 'links',
      '#links' => $this->helpfulLinks($request),
    );

    // No updates to run, so caches won't get flushed later.  Clear them now.
    drupal_flush_all_caches();
  }
  else {
    $build['help'] = array(
      '#markup' => '<p>' . $this->t('The version of Drupal you are updating from has been automatically detected.') . '</p>',
      '#weight' => -5,
    );
    if ($incompatible_count) {
      $build['start']['#title'] = $this->formatPlural(
      $count, 
      '1 pending update (@number_applied to be applied, @number_incompatible skipped)', 
      '@count pending updates (@number_applied to be applied, @number_incompatible skipped)', 
      array('@number_applied' => $count - $incompatible_count, '@number_incompatible' => $incompatible_count)
      );
    }
    else {
      $build['start']['#title'] = $this->formatPlural($count, '1 pending update', '@count pending updates');
    }
    // @todo Simplify with https://www.drupal.org/node/2548095
    $base_url = str_replace('/update.php', '', $request->getBaseUrl());
    $url = (new Url('system.db_update', array('op' => 'run')))->setOption('base_url', $base_url);
    $build['link'] = array(
      '#type' => 'link',
      '#title' => $this->t('Apply pending updates'),
      '#attributes' => array('class' => array('button', 'button--primary')),
      '#weight' => 5,
      '#url' => $url,
      '#access' => $url->access($this->currentUser()),
    );
  }

  return $build;
}