Understanding Code Fragments with Issue Reports

Code comments are vital for software development and maintenance. To supplement the code comments, researchers proposed various approach that generate code comments. The prior approaches take three sources: (1) programming experience, (2) code-comment pairs in source files, and (3) comments of similar code snippets. Most of their generated comments explain code functionalities, but programmers also need comments that explain why a code fragment was developed as it is. To meet the timely needs, in this paper, we introduce a new source, issue reports (e.g. maintenance types, symptoms, and purposes of modifications), to generate code comments. Issue reports contain rich information on how code was maintained. The valuable details of issue reports are useful to understand source code, especially when programmers learn why code was developed in a specific way. Towards this research direction, we propose the first approach, called ISSUECOMM, that builds the links between code fragments and issue reports. Our results show that it links more than 70% issue numbers that are written by programmers in code comments. Furthermore, the links built by our tool covers 4× bugs, and 10× other issues than the links written in manual comments. We present samples of our built links, and explain why our links are useful to describe the functionalities and the purpose of code.