Webform multi-page submit handler fires on every page

Question

I have created a couple of webform submit handlers before, but my new one fires on every page submit rather than when the last page is submitted.

How do I get the webform handler to only fire after the full form is submitted?

Below is what I have at the moment, which fires on each page:

namespace Drupal\the_api\Plugin\WebformHandler;

use Drupal\Core\Form\FormStateInterface;
use Drupal\webform\Plugin\WebformHandlerBase;
use Drupal\webform\WebformSubmissionInterface;

/**
 * Webform submission remote post handler.
 *
 * @WebformHandler(
 *   id = "membership_api_post",
 *   label = @Translation("New Membership to API"),
 *   category = @Translation("External"),
 *   description = @Translation("Posts a new membership through to the API."),
 *   cardinality = \Drupal\webform\Plugin\WebformHandlerInterface::CARDINALITY_UNLIMITED,
 *   results = \Drupal\webform\Plugin\WebformHandlerInterface::RESULTS_PROCESSED,
 *   submission = \Drupal\webform\Plugin\WebformHandlerInterface::SUBMISSION_REQUIRED,
 * )
 */
class NewMembershipWebformHandler extends WebformHandlerBase {

  /**
   * @param array $form
   * @param \Drupal\Core\Form\FormStateInterface $form_state
   * @param \Drupal\webform\WebformSubmissionInterface $webform_submission
   */
  public function submitForm(array &$form, FormStateInterface $form_state, WebformSubmissionInterface $webform_submission) {
    parent::submitForm($form, $form_state, $webform_submission);

    kint($form_state);

  }
}

Answer 1

You can use $webform_submission->getState() to determine if the submission is completed. The EmailWebformHandler includes decent examples on how to the submission state. I recommend trying to use WebformHandler::postSave() instead of WebformHandler::formSubmit().