Exploring a Hidden Feature in Drupal's Migrate API: Insights from Daniel Flanagan

Daniel Flanagan recently uncovered a lesser-known feature of the Drupal Migrate API that could simplify data migration processes. Published by Horizontal, Daniel's article reveals how using null as the source in a process pipeline allows the current value to be referenced easily, an option previously unknown even to the API's maintainers. This technique enables duplication of the pipeline's current value, as demonstrated with a "drupal+drupal" output in his example. 

While this trick enhances the flexibility of the Migrate API, its lack of documentation raises questions about its reliability and intended usage. Daniel's discovery has prompted re-evaluating what might be considered an undocumented feature or a potential glitch within the API's framework.