Config.php

<?php

namespace Drupal\migrate_drupal\Plugin\migrate\source\d8;

use Drupal\migrate\Row;
use Drupal\migrate_drupal\Plugin\migrate\source\DrupalSqlBase;

/**
 * Drupal 8+ configuration source from database.
 *
 * Available configuration keys:
 * - collections: (optional) The collection of configuration storage to retrieve
 *   from the source - can be a string or an array. If omitted, configuration
 *   objects of all available collections are retrieved.
 * - names: (optional) Names of configuration objects to retrieve from the
 *   source - can be a string or an array. If omitted, all available
 *   configuration objects are retrieved.
 *
 * Examples:
 *
 * @code
 * source:
 *   plugin: d8_config
 *   names:
 *     - node.type.article
 *     - node.type.page
 * @endcode
 *
 * In this example configuration objects of article and page content types are
 * retrieved from the source database.
 *
 * @code
 * source:
 *   plugin: d8_config
 *   collections: language.fr
 *   names:
 *     - node.type.article
 *     - node.type.page
 * @endcode
 *
 * In this example configuration objects are filtered by language.fr collection.
 * As a result, French versions of specified configuration objects are retrieved
 * from the source database.
 *
 * For additional configuration keys, refer to the parent classes.
 *
 * @see \Drupal\migrate\Plugin\migrate\source\SqlBase
 * @see \Drupal\migrate\Plugin\migrate\source\SourcePluginBase
 *
 * @MigrateSource(
 *   id = "d8_config",
 *   source_module = "system",
 * )
 */
class Config extends DrupalSqlBase {
    
    /**
     * {@inheritdoc}
     */
    public function query() {
        $query = $this->select('config', 'c')
            ->fields('c', [
            'collection',
            'name',
            'data',
        ]);
        if (!empty($this->configuration['collections'])) {
            $query->condition('collection', (array) $this->configuration['collections'], 'IN');
        }
        if (!empty($this->configuration['names'])) {
            $query->condition('name', (array) $this->configuration['names'], 'IN');
        }
        return $query;
    }
    
    /**
     * {@inheritdoc}
     */
    public function prepareRow(Row $row) {
        $row->setSourceProperty('data', unserialize($row->getSourceProperty('data')));
        return parent::prepareRow($row);
    }
    
    /**
     * {@inheritdoc}
     */
    public function fields() {
        return [
            'collection' => $this->t('The config object collection.'),
            'name' => $this->t('The config object name.'),
            'data' => $this->t('Serialized configuration object data.'),
        ];
    }
    
    /**
     * {@inheritdoc}
     */
    public function getIds() {
        $ids['collection']['type'] = 'string';
        $ids['name']['type'] = 'string';
        return $ids;
    }

}