code: public function actionList()
      {
          foreach ($this->getCommandDescriptions() as $command => $description) {
              $result = Yii::$app->createController($command);
              if ($result === false || !($result[0] instanceof Controller)) {
                  continue;
              }
              /** @var $controller Controller */
              list($controller, $actionID) = $result;
              $actions = $this->getActions($controller);
              if (!empty($actions)) {
                  $prefix = $controller->getUniqueId();
                  $this->stdout("$prefix\n");
                  foreach ($actions as $action) {
                      $this->stdout("$prefix/$action\n");
                  }
              }
          }
      }
docs: List all available controllers and actions in machine readable format.
  This is used for shell completion.
  @since 2.0.11