Effects of Adopting Code Review Bots on Pull Requests to OSS Projects

Reviewed by Greg Wilson / 2021-09-30
Keywords: Automation, Code Review

Several years ago, I grumbled that software tooling had basically stalled in the 1980s—that everything I used to write code today would have been familiar to my younger self. Prof. Peggy Storey corrected me, pointing out that social coding tools like Stack Overflow and Slack bots had changed programming every bit as much as linters and interactive debuggers.

Wessel2020 is a good look at what happens when a team adopts one of those tools: a bot that automatically runs code checks on pull requests and sends the results back to the PR's author. They found that adopting a code review bot:

  1. increases the number of monthly merged pull requests,
  2. decreases monthly non-merged pull requests, but
  3. decreases communication among developers.

Looking at the third result more closely, the authors find that the amount of communication as comments on the PR decreases. This seems to be because the number of comments depends on how long the PR is open; since adopting a code review bot leads to PRs being merged more quickly, it's not surprising that the number of comments would go down. In addition, the authors weren't able to look at out-of-band communication (e.g., via email or messaging), so the simple statement that communication decreases should be unpacked before it's shared.

Wessel2020 Mairieli Wessel, Alexander Serebrenik, Igor Wiese, Igor Steinmacher, and Marco A. Gerosa: "Effects of Adopting Code Review Bots on Pull Requests to OSS Projects". 2020 IEEE International Conference on Software Maintenance and Evolution (ICSME), 10.1109/icsme46990.2020.00011.

Software bots, which are widely adopted by Open Source Software (OSS) projects, support developers on several activities, including code review. However, as with any new technology adoption, bots may impact group dynamics. Since understanding and anticipating such effects is important for planning and management, we investigate how several activity indicators change after the adoption of a code review bot. We employed a regression discontinuity design on 1,194 software projects from GitHub. Our results indicate that the adoption of code review bots increases the number of monthly merged pull requests, decreases monthly non-merged pull requests, and decreases communication among developers. Practitioners and maintainers may leverage our results to understand, or even predict, bot effects on their projects' social interactions.