The Drupal migrations, despite their linearity in terms of definitions, contain a lot of inherited complexity. The reason is very intuitive: although the Migrate API is a supersystem that offers a very simple “interface” of interactions for the user-developer who wants to build migration processes, in reality several subsystems work by interacting with each other throughout a migration process: Entities, Database, Plugins…There are a lot of classes involved in even the simplest migration process. If we add the irrefutable fact that a migration will tend to generate errors in …