wadmiraal/drupal8_tdd_form_validation

<?php
/**
 * @file
 * Module hooks and callbacks.
 */

/**
 * File validation callback.
 *
 * Check the CSV is in the correct format, using commas as a separator, and
 * with at least 2 columns per row.
 *
 * @see file_validate()
 *
 * @param \Drupal\file\FileInterface $file
 *     The file to be validated.
 *
 * @return array
 *     List of validation issues, if any.
 */
function form_validation_validate_csv(\Drupal\file\FileInterface $file) {
  return \Drupal::service('form_validation.csv_parser')->validate($file);
}