The RequiredOrderCheck component, which appears in the Order Check stage of an order processing pipeline, ensures that the OrderForm's items list is not empty. If the list is empty, RequiredOrderCheck retrieves the message associated with the pur_noitems error from the MessageManager, and writes this message to the OrderForm’s _Purchase_Errors list.
If you are not running the Pipeline Editor in expert mode, the RequiredOrderCheck component is automatically inserted into the Order Check stage, but is not displayed in the Pipeline Editor user interface. This component appears in the user interface only if you run the Pipeline Editor in expert mode.