Let's Make Refactoring Tools User-extensible!

We present a framework for making a refactoring tool extensible, allowing users to define refactorings from scratch using the concrete syntax of the language, as well as to describe complex refactorings in a domain-specific language for scripting. We demonstrate the approach in practice through a series of examples. The extension framework is built into Wrangler, a tool for refactoring Erlang programs, but we argue that the approach is equally applicable to tools for other languages