Polyglot AST: Towards Enabling Polyglot Code Analysis

by Philémon Houdaille
DiverSE Coffee
Rennes, France


Today, a plethora of programming languages exists, each better suited for a particular concern. For example, Python is suited for data analysis but not web development, whereas JavaScript is the inverse. As software complexity grows and needs to address multiple concerns, different programming languages are often used in combination, despite the burden of bridging them (e.g., using Java Native Interface). Polyglot programming emerged as a solution allowing the seamless mixing of multiple programming languages. GraalVM and PolyNote are examples of runtimes allowing polyglot programming. However, there is a striking lack of support at design time for building and analyzing polyglot code. To the best of our knowledge, there is no uniform language-agnostic way of reasoning over multiple languages to provide seamless code analysis, since each language comes with its own form of Abstract Syntax Trees (AST). In this paper, we present an approach to build a uniform yet polyglot AST over polyglot code, so that it is easier to perform global analysis. We first motivate this challenge and identify the main requirements for building a polyglot AST. We then propose a proof of concept implementation of our solutions on GraalVM’s polyglot API. On top of the polyglot AST, we demonstrate the ability to implement several polyglot-specific analysis services, namely auto-completion, consistency checking, type inference, and rename refactoring.