When submitting a pull request (PR), developers often grapple with balancing the size of the PR. If it's too large, it overwhelms reviewers; if it's too small, it might create unnecessary overhead. This guide explores pull request size best practices, ideal PR size, and actionable steps for managing PR size to ensure your code reviews remain efficient and productive.
Why pull request size matters
Before diving into specific PR size guidelines, let's dig a bit deeper into why managing pull request size is so important:
- Review efficiency: Smaller PRs make it easier for reviewers to understand the changes without being overloaded with too much context. This helps cut down review time, too.
- Reduced complexity: Large pull requests often contain multiple unrelated changes, which increases the likelihood of introducing bugs or regressions.
- Faster feedback loops: Smaller PRs allow for quicker iterations and feedback, which are cornerstones of a more agile development process.
With these reasons in mind, let's explore some of the best practices for keeping your PRs manageable.
Guidelines for an ideal pull request size
The "ideal" PR size varies depending on your team's workflow and the nature of the project. However, certain general guidelines can help determine when a PR is optimally sized:
Aim to keep pull requests under 200 lines: Research suggests that pull requests under 200 lines of code get merged much faster, with the ideal length being around 50 lines.
Focus on a single feature or bug fix: A PR should only address one task at a time. Merging multiple changes into a single PR complicates the review process, so it's important to break down large tasks into smaller, self-contained units that can be reviewed independently.
Consider the number of files affected: Along with the number of lines, the number of files changed should remain limited. If too many files are touched, the review becomes harder to follow.
Use descriptive commit messages: When breaking larger tasks into multiple smaller PRs, use detailed commit messages to explain how each change relates to the overall task. This helps the reviewer understand the purpose of each change and that ensures context is not lost between PRs.
Best practices for managing pull request size
To put these PR size guidelines into practice, here are some actionable steps you can take to manage your PR size more effectively.
Break tasks down early on
During the planning phase, you should anticipate when a task might become too large for a single PR. If a feature seems like it will require hundreds of lines of code or touch many files, it's time to start thinking about how to break it into smaller pieces.
For example, if you're implementing a new feature like user authentication, consider breaking it down as follows:
- One PR for the backend API logic.
- A second PR for the user interface components.
- A third PR for any refactoring or test updates.
Each of these changes addresses one piece of the overall feature and keeps the PR sizes smaller and more digestible without compromising the review process.
Set internal PR size guidelines
Setting expectations and establishing a common understanding within your teams of the ideal pull request size is another important piece. You might agree to reject or flag PRs that exceed certain thresholds—e.g., more than 500 lines of code or changes that affect more than 10 files. These guidelines encourage developers to break down their work into manageable PRs.
Teams should also revisit and adjust these guidelines based on project complexity. For instance, smaller projects with tightly coupled components might require smaller PRs than a project with modular architecture.
Keep PRs atomic
Atomic PRs are those that stand on their own and can be merged without additional context. Each PR should achieve a clear goal (like fixing a bug or adding a feature) and not depend on other unmerged branches. Avoid mixing different types of changes (e.g., bug fixes with feature enhancements) within the same PR.
For example, a non-atomic PR might look like this:
- Fix bug A
- Add feature X
- Refactor method B
This type of PR becomes difficult to review because the changes are unrelated, and if one part requires further revision, the entire PR might get delayed. Instead, split it into three atomic PRs, each focused on one task for an easier review.
Perform self-reviews
Before assigning a PR to a reviewer, developers should do a quick self-review. This helps in trimming down unnecessary code and ensures comments and documentation are adequate. If the PR feels too large or complicated to the author, it’s almost guaranteed that reviewers will feel the same.
For example, run through the changes and ask:
- Are there unrelated changes that can be pulled out into a separate PR?
- Have I kept the focus on a single task?
- Can I add any explanations that will help the reviewer understand the context?
Avoid large refactors
Refactors, while necessary, can bloat a PR with a lot of code changes that are difficult to review. Instead of including a refactor in a feature or bug fix PR, handle refactors in separate pull requests to maintain clarity. If a refactor is large, break it down over several PRs to reduce the cognitive load on reviewers.
For example, if you are refactoring a legacy codebase, one PR might focus on renaming variables, while another addresses method restructuring. Keeping refactors and new feature development separate ensures reviews are more focused.
Leverage automated tools for efficiency
When combined with the pull request size best practices mentioned above, automated tools, like Graphite, make the review process significantly smoother. Smaller PRs are already easier to review manually, but Graphite takes this a step further by enabling stacking. This allows you to stack multiple PRs on top of each other so you can keep building without waiting on review.
Handling large PRs when they are unavoidable
Sometimes, despite best efforts, a feature or fix is too large to fit into a single manageable pull request. In such cases, here’s how to mitigate the complexity of reviewing large PRs:
Communicate early: Notify your team that a large PR is coming and give them time to prepare.
Provide detailed descriptions: Break down the changes in the PR description with bullet points for each major change. This makes it easier for reviewers to navigate the PR.
Use tags or labels: Labeling the PR as “large” or “needs more time” helps reviewers allocate time for an in-depth review. This prevents PRs from being rushed through and missing critical feedback.
Stack your PRs: By stacking, you can still adhere to PR size guidelines (like keeping under 200 lines) while ensuring that reviewers aren’t forced to tackle the entire feature in one attempt.
Takeaways
Managing pull request size is important for smooth collaboration and maintaining high code quality. By following PR size best practices, you make your changes easier to review, significantly reduce the risk of bugs, and accelerate feedback loops. Smaller, focused PRs not only enhance the review experience but also lead to faster, more efficient development. The key is finding the perfect balance—keeping PRs small enough for easy review without fragmenting tasks unnecessarily. Achieve this, and your team will work smarter, ship faster, and maintain higher-quality code with each release.
