UriLinkFormatter.php

<?php

namespace Drupal\Core\Field\Plugin\Field\FieldFormatter;

use Drupal\Core\Field\FormatterBase;
use Drupal\Core\Field\FieldItemListInterface;
use Drupal\Core\Url;

/**
 * Plugin implementation of the 'uri_link' formatter.
 *
 * @FieldFormatter(
 *   id = "uri_link",
 *   label = @Translation("Link to URI"),
 *   field_types = {
 *     "uri",
 *   }
 * )
 */
class UriLinkFormatter extends FormatterBase {
    
    /**
     * {@inheritdoc}
     */
    public function viewElements(FieldItemListInterface $items, $langcode) {
        $elements = [];
        foreach ($items as $delta => $item) {
            if (!$item->isEmpty()) {
                $elements[$delta] = [
                    '#type' => 'link',
                    '#url' => Url::fromUri($item->value),
                    '#title' => $item->value,
                ];
            }
        }
        return $elements;
    }

}