GenericFileFormatter.php

<?php

namespace Drupal\file\Plugin\Field\FieldFormatter;

use Drupal\Core\Field\FieldItemListInterface;

/**
 * Plugin implementation of the 'file_default' formatter.
 *
 * @FieldFormatter(
 *   id = "file_default",
 *   label = @Translation("Generic file"),
 *   field_types = {
 *     "file"
 *   }
 * )
 */
class GenericFileFormatter extends DescriptionAwareFileFormatterBase {
    
    /**
     * {@inheritdoc}
     */
    public function viewElements(FieldItemListInterface $items, $langcode) {
        $elements = [];
        foreach ($this->getEntitiesToView($items, $langcode) as $delta => $file) {
            $item = $file->_referringItem;
            $elements[$delta] = [
                '#theme' => 'file_link',
                '#file' => $file,
                '#description' => $this->getSetting('use_description_as_link_text') ? $item->description : NULL,
                '#cache' => [
                    'tags' => $file->getCacheTags(),
                ],
            ];
            // Pass field item attributes to the theme function.
            if (isset($item->_attributes)) {
                $elements[$delta] += [
                    '#attributes' => [],
                ];
                $elements[$delta]['#attributes'] += $item->_attributes;
                // Unset field item attributes since they have been included in the
                // formatter output and should not be rendered in the field template.
                unset($item->_attributes);
            }
        }
        return $elements;
    }

}