FieldInstanceOptionTranslation.php

<?php

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

use Drupal\migrate\MigrateExecutableInterface;
use Drupal\migrate\ProcessPluginBase;
use Drupal\migrate\Row;

/**
 * Determines the settings property and translation for boolean fields.
 *
 * @MigrateProcessPlugin(
 *   id = "d6_field_instance_option_translation",
 *   handle_multiples = TRUE
 * )
 */
class FieldInstanceOptionTranslation extends ProcessPluginBase {
    
    /**
     * {@inheritdoc}
     */
    public function transform($value, MigrateExecutableInterface $migrate_executable, Row $row, $destination_property) {
        list($field_type, $global_settings) = $value;
        $option_key = 0;
        $translation = '';
        if (isset($global_settings['allowed_values'])) {
            $list = explode("\n", $global_settings['allowed_values']);
            $list = array_map('trim', $list);
            $list = array_filter($list, 'strlen');
            switch ($field_type) {
                case 'boolean':
                    $option = preg_replace('/^option_/', '', $row->getSourceProperty('property'));
                    for ($i = 0; $i < 2; $i++) {
                        $value = $list[$i];
                        $tmp = explode("|", $value);
                        $original_option_key = isset($tmp[0]) ? $tmp[0] : NULL;
                        $option_key = $i === 0 ? 'off_label' : 'on_label';
                        // Find property with name matching the original option.
                        if ($option == $original_option_key) {
                            $translation = $row->getSourceProperty('translation');
                            break;
                        }
                    }
                    break;
                default:
            }
        }
        return [
            'settings.' . $option_key,
            $translation,
        ];
    }

}