materio-base-d7/sites/all/modules/contrib/fields/content_taxonomy/content_taxonomy_migrate.module

<?php

function content_taxonomy_migrate_content_migrate_field_alter(&$field_value, $instance_value) {
  if ($field_value['type'] == 'content_taxonomy') {
    $field_value['type'] = 'taxonomy_term_reference';
    $field_value['module'] = 'taxonomy';
    
    // transform field settings
    $old_settings = $field_value['settings'];
    $vocabulary = taxonomy_vocabulary_load($old_settings['vid']);
    $field_value['settings'] = array();
    $field_value['settings']['allowed_values'] = array();
    $field_value['settings']['allowed_values'][0]['vocabulary'] = $vocabulary->machine_name;
    $field_value['settings']['allowed_values'][0]['parent'] = $old_settings['parent'];
  }
}
  
function content_taxonomy_migrate_content_migrate_instance_alter(&$instance_value, $field_value) {
  if ($instance_value['widget_type'] == "content_taxonomy_autocomplete") {
    $instance_value['widget_type'] = 'taxonomy_autocomplete';
    $instance_value['widget']['type'] = 'taxonomy_autocomplete';
    $instance_value['widget']['module'] = 'taxonomy';
  }
  else if ($instance_value['widget_type'] == "content_taxonomy_options" || $instance_value['widget_type'] == "content_taxonomy_tree") {
    $instance_value['widget_type'] = 'options_buttons';
    $instance_value['widget']['type'] = 'options_buttons';
    $instance_value['widget']['module'] = 'options';
  }
  else if ($instance_value['widget_type'] == "content_taxonomy_select" || $instance_value['widget_type'] == 'content_taxonomy_hs') {
    $instance_value['widget_type'] = 'options_select';
    $instance_value['widget']['type'] = 'options_select';
    $instance_value['widget']['module'] = 'options';
  }
  
  // fix formatter
  foreach ($instance_value['display'] as $context => $settings) {
    if ($instance_value['display'][$context]['type'] == 'default') {
      $instance_value['display'][$context]['type'] = 'taxonomy_term_reference_plain';
    }
    else if ($instance_value['display'][$context]['type'] == 'link') {
      $instance_value['display'][$context]['type'] = 'taxonomy_term_reference_link';
    }
  }
}

function content_taxonomy_migrate_content_migrate_data_record_alter(&$record, $field) {
  // fill the taxonomy_index
  if ($field['type'] == 'taxonomy_term_reference') {
    if (variable_get('taxonomy_maintain_index_table', TRUE) && $field['storage']['type'] == 'field_sql_storage' && $record['entity_type'] == 'node') {
      if (isset($record[$field['field_name'] . "_tid"]) && $record[$field['field_name'] . "_tid"]) {
        $entity = node_load($record['entity_id']);
        db_delete('taxonomy_index')->condition('nid', $entity->nid)->condition('tid', $record[$field['field_name'] . "_tid"])->execute();
        $query = db_insert('taxonomy_index')->fields(array('nid', 'tid', 'sticky', 'created', ));
        $query->values(array(
          'nid' => $entity->nid,
          'tid' => $record[$field['field_name'] . "_tid"],
          'sticky' => $entity->sticky,
          'created' => $entity->created,
        ));
        $query->execute();
      }
    }
  }
}