FieldSettings.php

<?php

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

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

/**
 * @MigrateProcessPlugin(
 *   id = "d7_field_settings"
 * )
 */
class FieldSettings extends ProcessPluginBase {
    
    /**
     * {@inheritdoc}
     */
    public function transform($value, MigrateExecutableInterface $migrate_executable, Row $row, $destination_property) {
        $value = $row->getSourceProperty('settings');
        switch ($row->getSourceProperty('type')) {
            case 'image':
                if (!is_array($value['default_image'])) {
                    $value['default_image'] = [
                        'uuid' => '',
                    ];
                }
                break;
            case 'date':
            case 'datetime':
            case 'datestamp':
                $collected_date_attributes = is_numeric(array_keys($value['granularity'])[0]) ? $value['granularity'] : array_keys(array_filter($value['granularity']));
                if (empty(array_intersect($collected_date_attributes, [
                    'hour',
                    'minute',
                    'second',
                ]))) {
                    $value['datetime_type'] = 'date';
                }
                break;
            case 'taxonomy_term_reference':
                $value['target_type'] = 'taxonomy_term';
                break;
            case 'user_reference':
                $value['target_type'] = 'user';
                break;
            default:
                break;
        }
        return $value;
    }

}