Refactoring Support for Modularity Maintenance in Erlang

Low coupling between modules and high cohesion inside each module are the key features of good software architecture. Systems written in modern programming languages generally start with some reasonably well-designed module structure; however with continuous feature additions, modifications and bug fixes, software modularity gradually deteriorates; and there is a need for incrementally improving modularity to avoid the situation when the structure of the system becomes too complex to maintain. We demonstrate how Wrangler, a general-purpose refactoring tool for Erlang, could be used to maintain and improve the modularity of programs written in Erlang without dramatically changing the existing module structure. We identify a set of ''modularity smells'' and show how they can be detected by Wrangler and removed by way of a variety of refactorings implemented in Wrangler. Validation of the approach and usefulness of the tool are demonstrated by case studies.