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');
    }

}