Custom Preprocessing

In Drupal 7 there were numerous ways to preprocess data prior to migrating values. This was especially useful when inconsistencies in the data source needed to be addressed. One example I have dealt with in the past was migrating email addresses from an old system that didn’t check for properly formatted emails on its user fields. These errors would produce faulty data in the new Drupal site. I preprocessed the field data for the most common mistakes which reduced the amount of erroneous addresses brought over.