Vocabulary.php

<?php

namespace Drupal\taxonomy\Plugin\migrate\source\d7;

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

/**
 * Drupal 7 vocabularies source from database.
 *
 * For available configuration keys, refer to the parent classes.
 *
 * @see \Drupal\migrate\Plugin\migrate\source\SqlBase
 * @see \Drupal\migrate\Plugin\migrate\source\SourcePluginBase
 *
 * @MigrateSource(
 *   id = "d7_taxonomy_vocabulary",
 *   source_module = "taxonomy"
 * )
 */
class Vocabulary extends DrupalSqlBase {

  /**
   * {@inheritdoc}
   */
  public function query() {
    $query = $this
      ->select('taxonomy_vocabulary', 'v')
      ->fields('v', [
      'vid',
      'name',
      'description',
      'hierarchy',
      'module',
      'weight',
      'machine_name',
    ]);
    return $query;
  }

  /**
   * {@inheritdoc}
   */
  public function fields() {
    return [
      'vid' => $this
        ->t('The vocabulary ID.'),
      'name' => $this
        ->t('The name of the vocabulary.'),
      'description' => $this
        ->t('The description of the vocabulary.'),
      'hierarchy' => $this
        ->t('The type of hierarchy allowed within the vocabulary. (0 = disabled, 1 = single, 2 = multiple)'),
      'module' => $this
        ->t('Module responsible for the vocabulary.'),
      'weight' => $this
        ->t('The weight of the vocabulary in relation to other vocabularies.'),
      'machine_name' => $this
        ->t('Unique machine name of the vocabulary.'),
    ];
  }

  /**
   * {@inheritdoc}
   */
  public function prepareRow(Row $row) {

    // If the vocabulary being migrated is the one defined in the
    // 'forum_nav_vocabulary' variable, set the 'forum_vocabulary' source
    // property to true so we know this is the vocabulary used by Forum.
    if ($this
      ->variableGet('forum_nav_vocabulary', 0) == $row
      ->getSourceProperty('vid')) {
      $row
        ->setSourceProperty('forum_vocabulary', TRUE);
    }
    return parent::prepareRow($row);
  }

  /**
   * {@inheritdoc}
   */
  public function getIds() {
    $ids['vid']['type'] = 'integer';
    return $ids;
  }

}