An Empirical Study on the Usage and Evolution of Identifier Styles in Practice

Identifiers play an important role in helping developers comprehend and maintain source code. In practice, developers usually employ two widely-used identifier styles, i.e., snake case and camel case, to format identifiers to make them understandable and informative. Despite researchers have empirically investigated the impacts of identifier styles on code comprehension activities, the usage and evolution of identifier styles, however, have not been fully explored. How are individual identifier styles formed in practice? How would identifier styles change and evolve? What are the potential impacts of identifier style-changes? Questions like these are important but have not been fully answered yet. In this paper, we conducted an empirical study on 9,792 GitHub projects to gain some insights into these problems. Specifically, we first analyzed how different identifier styles were formed in real software projects. Next, we explored the change patterns of identifier styles along with the project evolution. Finally, we investigated the potential impacts as well as categories of identifier style-changes. Our empirical results achieved some interesting findings. For example, we first reported some identifier style-change patterns (e.g., snake case →camel case → snake case), which could help developers resolve style-change problems in practice. Our study also provided some hints for researchers and developers when they use specific identifier styles in programs. For example, when researchers explore the impacts of identifier styles on code comprehension, they are suggested to consider the imbalanced distribution phenomenon of individual identifier styles. Besides, it is worthwhile for developers to build an identifier style-change prediction and propagation tool to reduce the style-change costs.