FieldStorageConfigAccessControlHandler.php

<?php

namespace Drupal\field;

use Drupal\Core\Access\AccessResult;
use Drupal\Core\Entity\EntityAccessControlHandler;
use Drupal\Core\Entity\EntityInterface;
use Drupal\Core\Session\AccountInterface;

/**
 * Defines the access control handler for the field storage config entity type.
 *
 * @see \Drupal\field\Entity\FieldStorageConfig
 */
class FieldStorageConfigAccessControlHandler extends EntityAccessControlHandler {
  
  /**
   * {@inheritdoc}
   */
  protected function checkAccess(EntityInterface $entity, $operation, AccountInterface $account) {
    /** \Drupal\field\FieldStorageConfigInterface $entity */
    if ($operation === 'delete') {
      if ($entity->isLocked()) {
        return AccessResult::forbidden()->addCacheableDependency($entity);
      }
      else {
        return AccessResult::allowedIfHasPermission($account, 'administer ' . $entity->getTargetEntityTypeId() . ' fields')
          ->addCacheableDependency($entity);
      }
    }
    return AccessResult::allowedIfHasPermission($account, 'administer ' . $entity->getTargetEntityTypeId() . ' fields');
  }

}