Why and How Java Developers Break APIs

Modern software development depends on APIs to reuse code and increase productivity. As most software systems, these libraries and frameworks also evolve, which may break existing clients. However, the main reasons to introduce breaking changes in APIs are unclear. Therefore, in this paper, we report the results of an almost 4-month long field study with the developers of 400 popular Java libraries and frameworks. We configured an infrastructure to observe all changes in these libraries and to detect breaking changes shortly after their introduction in the code. After identifying breaking changes, we asked the developers to explain the reasons behind their decision to change the APIs. During the study, we identified 59 breaking changes, confirmed by the developers of 19 projects. By analyzing the developers' answers, we report that breaking changes are mostly motivated by the need to implement new features, by the desire to make the APIs simpler and with fewer elements, and to improve maintainability. We conclude by providing suggestions to language designers, tool builders, software engineering researchers and API developers.Comment: Accepted at International Conference on Software Analysis, Evolution and Reengineering, SANER 2018; 11 page

How Do Developers React to API Evolution? The Pharo Ecosystem Case

International audienceSoftware engineering research now considers that no system is an island, but it is part of an ecosystem involving other systems, developers, users, hardware,. .. When one system (e.g., a framework) evolves, its clients often need to adapt. Client developers might need to adapt to functionalities, client systems might need to be adapted to a new API, client users might need to adapt to a new User Interface. The consequences of such changes are yet unclear, what proportion of the ecosystem might be expected to react, how long might it take for a change to diffuse in the ecosystem, do all clients react in the same way? This paper reports on an exploratory study aimed at observing API evolution and its impact on a large-scale software ecosystem, Pharo, which has about 3,600 distinct systems, more than 2,800 contributors, and six years of evolution. We analyze 118 API changes and answer research questions regarding the magnitude, duration, extension, and consistency of such changes in the ecosystem. The results of this study help to characterize the impact of API evolution in large software ecosystems, and provide the basis to better understand how such impact can be alleviated

Managing concern interfaces

Programming languages provide various mechanisms to support information hiding. One problem with information hiding, however, is that providing a stable interface behind which to hide implementation details involves fixing in advance the services offered through the interface. We introduce a flexible approach to define and manage interfaces to achieve separation of concerns in evolving software. Our approach involves explicitly specifying interface and implementation classes for individual concerns, and automatically classifying implementation classes based on their relation to the interface. Our approach is supported by JMantlet, a tool that provides advanced interface management within an integrated development environment. We report on a case study of a large system that provides evidence that flexible interface management is desirable and adequately supported by our approach. 1