Empirical evaluation of code smells in open source projects: preliminary results

Open Source Software (OSS) now plays an important role in various industry domains. OSS is generally developed by highly experienced developers who have multiple perspectives. However, previous studies have indicated that OSS has quality limitations in software maintainability. In general, OSS developers typically focus on achieving the correct functionality. In contrast, in addition to focusing on building software functionality, software engineering practices also focus on the structure of the software and on its maintainability. Code with a well-designed structure is more likely to result in high quality software. To better understand how peer code review can reduce ``code smells" in existing OSS projects, we examined comments from code reviewers that identified code smells in OSS projects. This paper is a proof-of-concept that presents the preliminary results from an analysis of comments we obtained for two OSS projects, OpenStack and WikiMedia, both of which use the code review data repository called Gerrit. The preliminary results of this ongoing research show that code reviewers comment on only a small number of code smells. The full-scale results would contribute to the empirical body of validated knowledge in the field of OSS quality and code review.