Software refactoring and rewriting: from the perspective of code transformations

TL;DR

This paper presents a novel approach to software refactoring by modeling it as a series of code transformations, enabling automation and manual correctness analysis, demonstrated through two projects achieving significant simplification.

Contribution

It introduces a method inspired by compiler techniques to automate and analyze software refactoring processes using code transformations and pattern recognition.

Findings

Achieved 10-100x simplification in refactoring projects

Automated transformation sequences facilitate correctness analysis

Regular text processing exploits codebase-specific patterns

Abstract

To refactor already working code while keeping reliability, compatibility and perhaps security, we can borrow ideas from micropass/nanopass compilers. By treating the procedure of software refactoring as composing code transformations, and compressing repetitive transformations with automation tools, we can often obtain representations of refactoring processes short enough that their correctness can be analysed manually. Unlike in compilers, in refactoring we usually only need to consider the codebase in question, so regular text processing can be extensively used, fully exploiting patterns only present in the codebase. Aside from the direct application of code transformations from compilers, many other kinds of equivalence properties may also be exploited. In this paper, two refactoring projects are given as the main examples, where 10-100 times simplification has been achieved with the application of a few kinds of useful transformations.