FileField.php

<?php

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

use Drupal\file\Plugin\migrate\field\d6\FileField as D6FileField;
use Drupal\migrate\Plugin\MigrationInterface;
use Drupal\migrate_drupal\Attribute\MigrateField;
// cspell:ignore filefield

/**
 * MigrateField Plugin for Drupal 7 file fields.
 */
class FileField extends D6FileField {
  
  /**
   * {@inheritdoc}
   */
  public function getFieldWidgetMap() {
    return [
      'file_mfw' => 'file_generic',
      'filefield_widget' => 'file_generic',
    ];
  }
  
  /**
   * {@inheritdoc}
   */
  public function defineValueProcessPipeline(MigrationInterface $migration, $field_name, $data) {
    $process = [
      'plugin' => 'sub_process',
      'source' => $field_name,
      'process' => [
        'target_id' => 'fid',
        'display' => 'display',
        'description' => 'description',
      ],
    ];
    $migration->mergeProcessOfProperty($field_name, $process);
  }

}