Design smells in multi-language systems and bug-proneness: a survival analysis

Modern applications are often developed using a combination of programming languages and technologies. Multi-language systems offer opportunities for code reuse and the possibility to leverage the strengths of multiple programming languages. However, multi-language development may also impede code comprehension and increase maintenance overhead. As a result of this, developers may introduce design smells by making poor design and implementation choices. Studies on mono-language systems suggest that design smells may increase the risk of bugs and negatively impact software quality. However, the impacts of multi-language smells on software quality are still under-investigated. In this paper, we aim to examine the impacts of multi-language smells on software quality, bug-proneness in particular. We performed survival analysis comparing the time until a bug occurrence in files with and without multi-language design smells. To have qualitative insights into the impacts of multi-language design smells on software bug-proneness, we performed topic modeling and manual investigations, to capture the categories and characteristics of bugs that frequently occur in files with multi-language smells. Our investigation shows that (1) files with multi-language smells experience bugs faster than files without those smells, and non-smelly files have hazard rates 87.5% lower than files with smells, (2) files with some specific types of smells experience bugs faster than the other smells, and (3) bugs related to “programming errors”, “external libraries and features support issues”, and “memory issues” are the most dominant types of bugs that occur in files with multi-language smells. Through this study, we aim to raise the awareness of developers about the impacts of multi-language design smells, and help them prioritize maintenance activities.