update_get_update_list

update_get_update_list()

function update_get_update_list() {
  // Make sure that the system module is first in the list of updates.
  $ret = array('system' => array());

  $modules = drupal_get_installed_schema_version(NULL, FALSE, TRUE);
  foreach ($modules as $module => $schema_version) {
    // Skip uninstalled and incompatible modules.
    if ($schema_version == SCHEMA_UNINSTALLED || update_check_incompatibility($module)) {
      continue;
    }
    // Display a requirements error if the user somehow has a schema version
    // from the previous Drupal major version.
    if ($schema_version < \Drupal::CORE_MINIMUM_SCHEMA_VERSION) {
      $ret[$module]['warning'] = '<em>' . $module . '</em> module cannot be updated. Its schema version is ' . $schema_version . ', which is from an earlier major release of Drupal. You will need to <a href="https://www.drupal.org/node/2127611">migrate the data for this module</a> instead.';
      continue;
    }
    // Otherwise, get the list of updates defined by this module.
    $updates = drupal_get_schema_versions($module);
    if ($updates !== FALSE) {
      // \Drupal::moduleHandler()->invoke() returns NULL for non-existing hooks,
      // so if no updates are removed, it will == 0.
      $last_removed = \Drupal::moduleHandler()->invoke($module, 'update_last_removed');
      if ($schema_version < $last_removed) {
        $ret[$module]['warning'] = '<em>' . $module . '</em> module cannot be updated. Its schema version is ' . $schema_version . '. Updates up to and including ' . $last_removed . ' have been removed in this release. In order to update <em>' . $module . '</em> module, you will first <a href="https://www.drupal.org/upgrade">need to upgrade</a> to the last version in which these updates were available.';
        continue;
      }

      $updates = array_combine($updates, $updates);
      foreach (array_keys($updates) as $update) {
        if ($update == \Drupal::CORE_MINIMUM_SCHEMA_VERSION) {
          $ret[$module]['warning'] = '<em>' . $module . '</em> module cannot be updated. It contains an update numbered as ' . \Drupal::CORE_MINIMUM_SCHEMA_VERSION . ' which is reserved for the earliest installation of a module in Drupal ' . \Drupal::CORE_COMPATIBILITY . ', before any updates. In order to update <em>' . $module . '</em> module, you will need to install a version of the module with valid updates.';
          continue 2;
        }
        if ($update > $schema_version) {
          // The description for an update comes from its Doxygen.
          $func = new ReflectionFunction($module . '_update_' . $update);
          $description = str_replace(array("\n", '*', '/'), '', $func->getDocComment());
          $ret[$module]['pending'][$update] = "$update - $description";
          if (!isset($ret[$module]['start'])) {
            $ret[$module]['start'] = $update;
          }
        }
      }
      if (!isset($ret[$module]['start']) && isset($ret[$module]['pending'])) {
        $ret[$module]['start'] = $schema_version;
      }
    }
  }

  if (empty($ret['system'])) {
    unset($ret['system']);
  }
  return $ret;
}