JunGL

Abstract

Refactorings are behaviour-preserving program transformations, typically for improving the structure of existing code. A few of these transformations have been mechanised in interactive development environments. Many more refactorings have been proposed, and it would be desirable for programmers to script their own refactorings. Implementing such source-to-source transformations, however, is quite complex: even the most sophisticated development environments contain significant bugs in their refactoring tools.We present a domain-specific language for refactoring, named JunGL. It manipulates a graph representation of the program: all information about the program, including ASTs for its compilation units, variable binding, control flow and so on is represented in a uniform graph format. The language is a hybrid of a functional language (in the style of ML) and a logic query language (akin to Datalog). JunGL furthermore has a notion of demand-driven evaluation for constructing computed information in the graph, such as control flow edges. Borrowing from earlier work on the specification of compiler optimisations, JunGL uses socalled 'path queries' to express dataflow properties.We motivate the design of JunGL via a number of nontrivial refactorings, and describe its implementation on the .NET platform.

Trustworthy Refactoring via Decomposition and Schemes: A Complex Case Study

“…Some of these define the entire code transformation logic including term-level rewriting, while some only offer a formalism for composing atomic steps in a convenient way. Leitdo [9] gives an executable, rewritebased refactoring language with expressive patterns, Verbaere [21] proposes a compact, representationlevel formalism for executable definitions. These formalisms are expressive and language-independent, but at this generality they cannot support correctness checks for refactoring definitions.…”

Towards Trustworthy Refactoring in Erlang

“…Padioleau et al [16] propose a transformation language incorporating semantic conditions into the textual patterns; however, they use it for specifying patches rather than refactorings. Verbaere [23] proposes a compact, representation-level formalism for executable definitions; it is language-independent, but does not give support for verifying the correctness of refactorings. For Erlang, our previous work [2] drafts a refactoring language, solely focusing on simplicity and interpretability.…”

Object-oriented transformations for extracting aspects

“…Early work in this area was done by Darlington and Burstall, concerning transformations to improve the performance of functional programs [5]. More recent systems include Stratego [30], TXL [11], and JunGL [29]. Stratego is a transformation system based on the paradigm of rewriting rules and strategies to control the process of transforming the program code.…”