TelephoneField.php

<?php

namespace Drupal\telephone\Plugin\migrate\field\d7;

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

/**
 * @MigrateField(
 *   id = "telephone",
 *   core = {7},
 *   source_module = "telephone",
 *   destination_module = "telephone"
 * )
 */
class TelephoneField extends FieldPluginBase {
    
    /**
     * {@inheritdoc}
     */
    public function getFieldWidgetMap() {
        // The widget IDs are identical in Drupal 7 and 8, so we do not need any
        // mapping.
        return [];
    }
    
    /**
     * {@inheritdoc}
     */
    public function getFieldFormatterMap() {
        return [
            'text_plain' => 'string',
            'telephone_link' => 'telephone_link',
        ];
    }

}