An Empirical Study of Refactoring Engine Bugs

TL;DR

This paper presents the first systematic study of refactoring engine bugs by analyzing bugs arising in three popular refactoring engines (i.e., Eclipse, IntelliJ IDEA, and Netbeans) according to their refactoring types, symptoms, root causes, and triggering conditions.

Abstract

Refactoring is a critical process in software development, aiming at improving the internal structure of code while preserving its external behavior. Refactoring engines are integral components of modern Integrated Development Environments (IDEs) and can automate or semi-automate this process to enhance code readability, reduce complexity, and improve the maintainability of software products. Like traditional software systems, refactoring engines can generate incorrect refactored programs, resulting in unexpected behaviors or even crashes. In this paper, we present the first systematic study of refactoring engine bugs by analyzing bugs arising in three popular refactoring engines (i.e., Eclipse, IntelliJ IDEA, and Netbeans). We analyzed these bugs according to their refactoring types, symptoms, root causes, and triggering conditions. We obtained 12 findings and provided a series of valuable guidelines for future work on refactoring bug detection and debugging. Furthermore, our transferability study revealed 130 new bugs in the latest version of those refactoring engines. Among the 21 bugs we submitted, 10 bugs are confirmed by their developers, and seven of them have already been fixed.

Figures (11)

• Figure 1: The general workflow of a refactoring engine
• Figure 2: Make Static refactoring erroneously changes method call
• Figure 3: Inline method refactoring leads to changes in access permissions
• Figure 4: IntelliJ IDEA fails to detect input variable if code fragment is located in unreachable else branch, the extracted method contains syntax error
• Figure 6: Bug Distribution by Root Causes