webform_product.module

<?php

use Drupal\Component\Plugin\Factory\DefaultFactory;
use Drupal\Core\Form\FormStateInterface;
use Drupal\webform_product\WebFormProductFormHelper;

/**
 * Implements hook_element_info_alter().
 */
function webform_product_element_info_alter(array &$info) {
  $definitions = \Drupal::service('plugin.manager.webform_product')->getDefinitions();
  foreach ($definitions as $id => $definition) {
    /** @var \Drupal\Component\Plugin\PluginManagerInterface $pluginManager */
    if (isset($info[$id])) {
      $info[$id]['#process'][] = [DefaultFactory::getPluginClass($id, $definition), 'process'];
    }
  }
}

/**
 * Implements hook_form_FORM_ID_alter().
 */
function webform_product_form_webform_ui_element_form_alter(&$form, FormStateInterface $form_state, $form_id) {
  $form['properties']['element']['#process'][] = [WebFormProductFormHelper::class, 'processElementForm'];
}

/**
 * Implements hook_webform_submission_form_alter().
 */
function webform_product_webform_submission_form_alter(array &$form, FormStateInterface $form_state, $form_id) {
  $form['actions']['submit']['#submit'][] = [WebFormProductFormHelper::class, 'submissionToCart'];
}