KtSpoon: Modelling Kotlin by extending Spoon’s Java Metamodel

Sammanfattning: Kotlin is a relatively new language that has received much attention since its first stable release in February 2016. Despite the fast growth of the language, there is a lack of libraries to provide an intuitive, typed abstract syntax tree (AST). Recognizing the utility of user-friendly ASTs with support for various analysis and transformation tasks, we make a first contribution towards bringing one for Kotlin with KtSpoon. Kotlin’s interoperability capabilities with Java enables exploitation of Java’s mature echo system and we propose the use of the Spoon library with its Java metamodel as a base for a model of Kotlin. We show the feasibility of this approach with KtSpoon, which is implemented through small additions to the Spoon metamodel. It consists of a tree builder that outputs a Spoon AST from Kotlin source code and a pretty-printer that prints it back to source code. Through an empirical study, we find out that KtSpoon accurately can represent the full Kotlin language. We conclude that while it is possible to model the Kotlin language with small modifications to the Spoon metamodel, it will likely require a partial reimplementation for it to be an intuitive model for developers.