class ConfigWithFieldEntityClone

class ConfigWithFieldEntityClone extends ConfigEntityCloneBase {
    
    /**
     * {@inheritdoc}
     */
    public function cloneEntity(EntityInterface $entity, EntityInterface $cloned_entity, array $properties = []) {
        $cloned_entity = parent::cloneEntity($entity, $cloned_entity, $properties);
        $bundle_of = $cloned_entity->getEntityType()
            ->getBundleOf();
        if ($bundle_of) {
            $this->cloneFields($entity->id(), $cloned_entity->id(), $bundle_of);
        }
        $view_displays = \Drupal::service('entity_display.repository')->getFormModes($bundle_of);
        $view_displays = array_merge($view_displays, [
            'default' => 'default',
        ]);
        if (!empty($view_displays)) {
            $this->cloneDisplays('form', $entity->id(), $cloned_entity->id(), $view_displays, $bundle_of);
        }
        $view_displays = \Drupal::service('entity_display.repository')->getViewModes($bundle_of);
        $view_displays = array_merge($view_displays, [
            'default' => 'default',
        ]);
        if (!empty($view_displays)) {
            $this->cloneDisplays('view', $entity->id(), $cloned_entity->id(), $view_displays, $bundle_of);
        }
        return $cloned_entity;
    }
    
    /**
     * Clone all fields. Each field re-use existing field storage.
     *
     * @param string $entity_id
     *   The base entity ID.
     * @param string $cloned_entity_id
     *   The cloned entity ID.
     * @param string $bundle_of
     *   The bundle of the cloned entity.
     */
    protected function cloneFields($entity_id, $cloned_entity_id, $bundle_of) {
        
        /** @var \Drupal\Core\Entity\EntityFieldManager $field_manager */
        $field_manager = \Drupal::service('entity_field.manager');
        $fields = $field_manager->getFieldDefinitions($bundle_of, $entity_id);
        foreach ($fields as $field_definition) {
            if ($field_definition instanceof FieldConfigInterface) {
                if ($this->entityTypeManager
                    ->hasHandler($this->entityTypeManager
                    ->getDefinition($field_definition->getEntityTypeId())
                    ->id(), 'entity_clone')) {
                    
                    /** @var \Drupal\entity_clone\EntityClone\EntityCloneInterface $field_config_clone_handler */
                    $field_config_clone_handler = $this->entityTypeManager
                        ->getHandler($this->entityTypeManager
                        ->getDefinition($field_definition->getEntityTypeId())
                        ->id(), 'entity_clone');
                    $field_config_properties = [
                        'id' => $field_definition->getName(),
                        'label' => $field_definition->label(),
                        'skip_storage' => TRUE,
                    ];
                    $cloned_field_definition = $field_definition->createDuplicate();
                    $cloned_field_definition->set('bundle', $cloned_entity_id);
                    $field_config_clone_handler->cloneEntity($field_definition, $cloned_field_definition, $field_config_properties);
                }
            }
        }
    }
    
    /**
     * Clone all fields. Each field re-use existing field storage.
     *
     * @param string $type
     *   The type of display (view or form).
     * @param string $entity_id
     *   The base entity ID.
     * @param string $cloned_entity_id
     *   The cloned entity ID.
     * @param array $view_displays
     *   All view available display for this type.
     * @param string $bundle_of
     *   The bundle of the cloned entity.
     */
    protected function cloneDisplays($type, $entity_id, $cloned_entity_id, array $view_displays, $bundle_of) {
        foreach ($view_displays as $view_display_id => $view_display) {
            
            /** @var \Drupal\Core\Entity\Display\EntityDisplayInterface $display */
            $display = $this->entityTypeManager
                ->getStorage('entity_' . $type . '_display')
                ->load($bundle_of . '.' . $entity_id . '.' . $view_display_id);
            if ($display) {
                
                /** @var \Drupal\entity_clone\EntityClone\EntityCloneInterface $view_display_clone_handler */
                $view_display_clone_handler = $this->entityTypeManager
                    ->getHandler($this->entityTypeManager
                    ->getDefinition($display->getEntityTypeId())
                    ->id(), 'entity_clone');
                $view_display_properties = [
                    'id' => $bundle_of . '.' . $cloned_entity_id . '.' . $view_display_id,
                ];
                $cloned_view_display = $display->createDuplicate();
                $cloned_view_display->set('bundle', $cloned_entity_id);
                $view_display_clone_handler->cloneEntity($display, $cloned_view_display, $view_display_properties);
            }
        }
    }

}