A large-scale empirical exploration on refactoring activities in open source software projects

Abstract

• Developers do not refactor source code frequently. • Developers adopt refactoring mainly to improve the understandability of source code. • Developers tend to not perform refactor in the proximity of a new system's release. • Refactoring tasks are mainly scheduled after the system's structure is stable. • Source code files are most likely to be refactored by their owners rather than others. Refactoring is a well-established practice that aims at improving the internal structure of a software system without changing its external behavior. Existing literature provides evidence of how and why developers perform refactoring in practice. In this paper, we continue on this line of research by performing a large-scale empirical analysis of refactoring practices in 200 open source systems. Specifically, we analyze the change history of these systems at commit level to investigate: (i) whether developers perform refactoring operations and, if so, which are more diffused and (ii) when refactoring operations are applied, and (iii) which are the main developer-oriented factors leading to refactoring. Based on our results, future research can focus on enabling automatic support for less frequent refactorings and on recommending refactorings based on the developer's workload, project's maturity and developer's commitment to the project.