Does the Role Matter? An Investigation of the Code Quality of Casual Contributors in GitHub

For popular Open Source Software (OSS) projects there are always a large number of worldwide developers who have been glued to making code contributions, while most of these developers play the role of casual contributors due to their very limited code commits (for fixing defects and enhancing features, casually). The frequent turnover of such group of casual developers and the wide variations among their coding experiences challenge the project management on code and quality. This paper describes a case study which aims to estimate the quality of code made by casual contributors in 21 popular GitHub projects. The results of this case study show that: (1) casual contributors introduced greater quantity and severity of Code Quality Issues (CQIs) than main contributors; (2) developers who contribute in different projects as main and casual contributors didn't perform statistically differently in terms of code quality; (3) casual contributors who have few project stars introduced more CQIs than those who have many. Furthermore, the paper lists the CQI categories which are most frequently introduced by casual contributors in the investigated projects. These findings provide valuable insights into code quality in the OSS context, and can guide OSS developers in improving the quality of the code contributions.