class FieldConfigDeleteForm

class FieldConfigDeleteForm extends EntityDeleteForm {
    
    /**
     * The entity type bundle info service.
     *
     * @var \Drupal\Core\Entity\EntityTypeBundleInfoInterface
     */
    protected $entityTypeBundleInfo;
    
    /**
     * Constructs a new FieldConfigDeleteForm object.
     *
     * @param \Drupal\Core\Entity\EntityTypeBundleInfoInterface $entity_type_bundle_info
     *   The entity type bundle info service.
     */
    public function __construct(EntityTypeBundleInfoInterface $entity_type_bundle_info) {
        $this->entityTypeBundleInfo = $entity_type_bundle_info;
    }
    
    /**
     * {@inheritdoc}
     */
    public static function create(ContainerInterface $container) {
        return new static($container->get('entity_type.bundle.info'));
    }
    
    /**
     * {@inheritdoc}
     */
    public function buildForm(array $form, FormStateInterface $form_state) {
        $form = parent::buildForm($form, $form_state);
        // If we are adding the field storage as a dependency to delete, then that
        // will list the field as a dependency. That is confusing, so remove it.
        // Also remove the entity type and the whole entity deletions details
        // element if nothing else is in there.
        if (isset($form['entity_deletes']['field_config']['#items']) && isset($form['entity_deletes']['field_config']['#items'][$this->entity
            ->id()])) {
            unset($form['entity_deletes']['field_config']['#items'][$this->entity
                ->id()]);
            if (empty($form['entity_deletes']['field_config']['#items'])) {
                unset($form['entity_deletes']['field_config']);
                if (!Element::children($form['entity_deletes'])) {
                    $form['entity_deletes']['#access'] = FALSE;
                }
            }
        }
        return $form;
    }
    
    /**
     * {@inheritdoc}
     */
    protected function getConfigNamesToDelete(ConfigEntityInterface $entity) {
        
        /** @var \Drupal\field\FieldStorageConfigInterface $field_storage */
        $field_storage = $entity->getFieldStorageDefinition();
        $config_names = [
            $entity->getConfigDependencyName(),
        ];
        // If there is only one bundle left for this field storage, it will be
        // deleted too, notify the user about dependencies.
        if (count($field_storage->getBundles()) <= 1) {
            $config_names[] = $field_storage->getConfigDependencyName();
        }
        return $config_names;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getCancelUrl() {
        return FieldUI::getOverviewRouteInfo($this->entity
            ->getTargetEntityTypeId(), $this->entity
            ->getTargetBundle());
    }
    
    /**
     * {@inheritdoc}
     */
    public function submitForm(array &$form, FormStateInterface $form_state) {
        $field_storage = $this->entity
            ->getFieldStorageDefinition();
        $bundles = $this->entityTypeBundleInfo
            ->getBundleInfo($this->entity
            ->getTargetEntityTypeId());
        $bundle_label = $bundles[$this->entity
            ->getTargetBundle()]['label'];
        if ($field_storage && !$field_storage->isLocked()) {
            $this->entity
                ->delete();
            $this->messenger()
                ->addStatus($this->t('The field %field has been deleted from the %type content type.', [
                '%field' => $this->entity
                    ->label(),
                '%type' => $bundle_label,
            ]));
        }
        else {
            $this->messenger()
                ->addError($this->t('There was a problem removing the %field from the %type content type.', [
                '%field' => $this->entity
                    ->label(),
                '%type' => $bundle_label,
            ]));
        }
        $form_state->setRedirectUrl($this->getCancelUrl());
        // Fields are purged on cron. However field module prevents disabling modules
        // when field types they provided are used in a field until it is fully
        // purged. In the case that a field has minimal or no content, a single call
        // to field_purge_batch() will remove it from the system. Call this with a
        // low batch limit to avoid administrators having to wait for cron runs when
        // removing fields that meet this criteria.
        field_purge_batch(10);
    }

}