Tool Support for Managing Clone Refactorings to Facilitate Code Review in Evolving Software

Abstract

Developers often perform copy-and-paste activities. This practice causes the similar code fragment (aka code clones) to be scattered throughout a code base. Refactoring for clone removal is beneficial, preventing clones from having negative effects on software quality, such as hidden bug propagation and unintentional inconsistent changes. However, recent research has provided evidence that factoring out clones is not always to reduce the risk of introducing defects, and it is often difficult or impossible to remove clones using standard refactoring techniques. To investigate which or how clones can be refactored, developers typically spend a significant amount of their time managing individual clone instances or clone groups scattered across a large code base. To address the problem, this paper presents a technique for managing clone refactorings, Pattern-based clone Refactoring Inspection (PRI), using refactoring pattern templates. By matching the refactoring pattern templates against a code base, it summarizes refactoring changes of clones, and detects the clone instances not consistently factored out as potential anomalies. PRI also provides novel visualization user interfaces specifically designed for inspecting clone refactorings. In the evaluation, PRI analyzes clone instances in six open source projects. It identifies clone refactorings with 94.1% accuracy and detects inconsistent refactorings with 98.4% accuracy. Our results show that PRI should help developers effectively inspect evolving clones and correctly apply refactorings to clone groups.