TextDefaultFormatter.php

<?php

namespace Drupal\text\Plugin\Field\FieldFormatter;

use Drupal\Core\Field\Attribute\FieldFormatter;
use Drupal\Core\Field\FormatterBase;
use Drupal\Core\Field\FieldItemListInterface;
use Drupal\Core\StringTranslation\TranslatableMarkup;

/**
 * Plugin implementation of the 'text_default' formatter.
 */
class TextDefaultFormatter extends FormatterBase {
    
    /**
     * {@inheritdoc}
     */
    public function viewElements(FieldItemListInterface $items, $langcode) {
        $elements = [];
        // The ProcessedText element already handles cache context & tag bubbling.
        // @see \Drupal\filter\Element\ProcessedText::preRenderText()
        foreach ($items as $delta => $item) {
            $elements[$delta] = [
                '#type' => 'processed_text',
                '#text' => $item->value,
                '#format' => $item->format,
                '#langcode' => $item->getLangcode(),
            ];
        }
        return $elements;
    }

}