TestFieldApplicableFormatter.php

<?php

declare (strict_types=1);
namespace Drupal\field_test\Plugin\Field\FieldFormatter;

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

/**
 * Plugin implementation of the 'field_test_applicable' formatter.
 *
 * It is applicable to test_field fields unless their name is 'deny_applicable'.
 */
class TestFieldApplicableFormatter extends FormatterBase {
    
    /**
     * {@inheritdoc}
     */
    public static function isApplicable(FieldDefinitionInterface $field_definition) {
        return $field_definition->getName() != 'deny_applicable';
    }
    
    /**
     * {@inheritdoc}
     */
    public function viewElements(FieldItemListInterface $items, $langcode) {
        return [
            '#markup' => 'Nothing to see here',
        ];
    }

}