edlp_d8/core/themes/stable/stable.theme

<?php

/**
 * @file
 * Functions to support theming in the Stable theme.
 */

use Drupal\Component\Utility\Html;

/**
 * Implements template_preprocess_links().
 */
function stable_preprocess_links(&$variables) {
  // @deprecated in Drupal 8.0.x and will be removed before 9.0.0. This feature
  // of adding a class based on the associative key can cause CSS class name
  // conflicts.
  if (!empty($variables['links'])) {
    foreach ($variables['links'] as $key => $value) {
      if (!is_numeric($key)) {
        $class = Html::getClass($key);
        $variables['links'][$key]['attributes']->addClass($class);
      }
    }
  }
}