<?php

/**
 * @file
 * Install, update and uninstall functions for the field module.
 */

/**
 * Removes the stale 'target_bundle' storage setting on entity_reference fields.
 */
function field_update_8001() {
  $config = \Drupal::configFactory();
  /** @var \Drupal\Core\Field\FieldTypePluginManager $field_type_manager */
  $field_type_manager = \Drupal::service('plugin.manager.field.field_type');
  $item_class = 'Drupal\Core\Field\Plugin\Field\FieldType\EntityReferenceItem';

  // Iterate on all fields storage.
  foreach ($config->listAll('field.storage.') as $field_id) {
    $field_storage = $config->getEditable($field_id);
    $class = $field_type_manager->getPluginClass($field_storage->get('type'));

    // Deal only with entity reference fields and descendants.
    if ($class == $item_class || is_subclass_of($class, $item_class)) {
      // Remove 'target_bundle' from settings.
      $field_storage->clear('settings.target_bundle')->save(TRUE);
    }
  }
}