LinkField.php

<?php

namespace Drupal\link\Plugin\migrate\field\d6;

use Drupal\migrate\Plugin\MigrationInterface;
use Drupal\migrate_drupal\Plugin\migrate\field\FieldPluginBase;

/**
 * @MigrateField(
 *   id = "link",
 *   core = {6},
 *   type_map = {
 *     "link" = "link",
 *   },
 *   source_module = "link",
 *   destination_module = "link"
 * )
 */
class LinkField extends FieldPluginBase {
    
    /**
     * {@inheritdoc}
     */
    public function getFieldFormatterMap() {
        // See d6_field_formatter_settings.yml and FieldPluginBase
        // alterFieldFormatterMigration().
        return [
            'default' => 'link',
            'plain' => 'link',
            'absolute' => 'link',
            'title_plain' => 'link',
            'url' => 'link',
            'short' => 'link',
            'label' => 'link',
            'separate' => 'link_separate',
        ];
    }
    
    /**
     * {@inheritdoc}
     */
    public function defineValueProcessPipeline(MigrationInterface $migration, $field_name, $data) {
        $process = [
            'plugin' => 'field_link',
            'source' => $field_name,
        ];
        $migration->mergeProcessOfProperty($field_name, $process);
    }

}