FieldInstanceOptionTranslation.php

<?php

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

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

/**
 * Determines the settings property and translation for boolean fields.
 *
 * @MigrateProcessPlugin(
 *   id = "d7_field_instance_option_translation",
 *   handle_multiples = TRUE
 * )
 */
class FieldInstanceOptionTranslation extends ProcessPluginBase {
    
    /**
     * {@inheritdoc}
     */
    public function transform($value, MigrateExecutableInterface $migrate_executable, Row $row, $destination_property) {
        [
            $type,
            $data,
        ] = $value;
        $data = unserialize($data);
        $property = $row->getSourceProperty('property');
        $option_key = $property == 0 ? 'off_label' : 'on_label';
        $translation = '';
        if (isset($data['settings']['allowed_values'])) {
            $allowed_values = $data['settings']['allowed_values'];
            switch ($type) {
                case 'boolean':
                    if (isset($allowed_values[$property])) {
                        $translation = $row->getSourceProperty('translation');
                        break;
                    }
                    break;
                default:
            }
        }
        return [
            'settings.' . $option_key,
            $translation,
        ];
    }

}