Eve Matthaey

Migrating a massive, actively developed codebase from one language to another is a daunting challengeespecially when the goal is to maximize developer productivity and long-term maintainability. At Meta, we embarked on a multi-year journey to translate tens of millions of lines of Java code, going far beyond incremental adoption to pursue a full-scale, automated migration.
In this talk, Ill share the technical and organizational lessons learned, with a focus on the custom refactoring infrastructure we built to make it possible. Ill discuss how we leveraged metaprogramming, static analysis, and even runtime data collection to tackle the thorniest issueslike null safety and dependency graph complexitywhile minimizing developer toil and risk.