In today’s rapidly evolving software development landscape, increasingly complex systems present new challenges in code reviews. As projects grow in size and scope, efficient code review processes become essential to maintain code quality and developer productivity. By understanding and categorizing pull requests (PRs), developers can streamline reviews, improve code quality, and foster better collaboration. Research supports the idea that clear classification of PRs can lead to more efficient and productive code reviews.1 2 In this essay, we will explore the classification of pull requests into three fundamental categories—Features, Refactors, and Updates—and discuss their impact on the code review process.
Class I: Features
Features represent the core advancements and additions to a codebase, introducing new functionalities or modifying existing ones. These changes are crucial for software evolution and enhancing user experiences. Class I PRs are characterized by:
- Predominantly line additions or deletions
- Modifications to public interfaces such as arguments, public methods, fields, or literal interfaces.
- Updates or additions to tests to ensure the new or altered functionality works as intended.
Features are the driving force behind software development, enabling products to meet new requirements and improve user satisfaction.
Example
Imagine a typical Feature PR involving the addition of a new API endpoint. This PR would include new code for the endpoint, updates to the interface to accommodate the new functionality, and tests to ensure the endpoint works correctly.
Class II: Refactors
Refactors are internal modifications aimed at improving code readability, maintainability, or performance without altering its external behavior. These changes make the codebase cleaner and more efficient. Class II PRs typically include:
- A mix of additions and deletions, often balancing each other out.
- No changes to public interfaces, ensuring the software’s external behavior remains consistent.
- (Usually) No need for test updates, as the functionality remains unchanged.
Refactors are essential for maintaining a healthy codebase, making it easier for developers to understand and work with the code over time.
Example
A Refactor PR might focus on improving code readability by renaming variables and functions to more meaningful names, reorganizing methods for better logical flow, and removing redundant code. These changes do not alter the functionality but make the code easier to maintain.
Class III: Updates
Updates encompass changes to existing features, which may include bugfixes, performance improvements, or modifications to enhance existing functionality. These changes are observable and typically require updates to tests to confirm that the issue has been resolved or the improvement is effective. Class III PRs are characterized by:
- An almost equal number of additions and deletions.
- Potential changes to public interfaces to implement the necessary improvements.
- Necessary updates to tests to verify the changes.
Updates are crucial for maintaining software reliability and user satisfaction, ensuring that the software performs as expected.
Example
Consider an Update PR that improves the performance of an existing feature causing delays under specific conditions. This PR would involve code changes to optimize the feature, possibly updates to public interfaces if necessary, and new or updated tests to ensure the improvement is effective.
The ideal pull-request
An ideal PR is focused and belongs to a single primary class of changes. It should be small, manageable, and dedicated to one purpose, whether it’s adding a feature, refactoring code, or updating an existing feature. Such PRs are easier to review, test, and integrate into the codebase, reducing the risk of introducing new issues.
Challenges and mixed-class PRs
While the ideal PR belongs to a single class, mixed-class PRs are common in larger projects. These PRs can be more challenging to review due to their complexity and the cognitive load they impose on reviewers.
Class IV-A: Update-Refactors
These PRs combine updates with refactoring changes. They often face criticism due to the difficulty in distinguishing between update-related changes and refactor-related changes. The lack of tests for the refactoring portion makes the diff hard to follow, complicating the review process.
Why Problematic?
Update-Refactor PRs blend the urgency and importance of updates with the less critical, but still valuable, refactoring tasks. This combination can obscure the main purpose of the PR, making it difficult for reviewers to prioritize their focus. The need to verify both the updates and the refactoring changes can lead to longer review times and increase the likelihood of errors slipping through. Additionally, the cognitive load increases as reviewers must switch contexts between understanding the update and assessing the refactoring efforts.
Class IV-B: Feature-Refactors
Similar to IV-A, these PRs include both new features and refactoring. They can be challenging to review as the introduction of new functionality is intertwined with internal code improvements, making it hard to assess each aspect independently.
Why problematic?
Feature-Refactor PRs can be problematic because they mix strategic, high-level changes with tactical, low-level improvements. This dual focus can dilute the reviewer’s attention, making it harder to ensure that the new feature works correctly and that the refactoring is effective. Reviewers may miss critical interactions between the new feature and the refactored code, leading to potential integration issues or unforeseen bugs.
Class IV-C: Update-Features
These PRs are particularly problematic as they attempt to update existing features while simultaneously adding new features. They are usually large and complex, requiring significant effort to understand the interplay between the updates and the new functionality.
Why problematic?
Update-Feature PRs are the most challenging because they require reviewers to juggle understanding the update, verifying the change, and evaluating the new feature. This combination can lead to confusion, as reviewers may struggle to separate the different types of changes and their impacts. The complexity of these PRs can result in longer review times, higher cognitive load, and a greater chance of introducing new bugs or missing critical issues.
Class V: Balls of Mud
Occasionally, a PR mixes all types of changes together—features, refactors, and updates—resulting in an unwieldy and massive diff. These PRs are the hardest to review, often leading to confusion and potential oversight of important details
Why problematic?
Balls of Mud PRs are essentially a worst-case scenario in code reviews. They present an overwhelming number of changes that can obscure the purpose and rationale behind each modification. Reviewers can become bogged down in the sheer volume of changes, leading to review fatigue and the potential for important issues to be overlooked. The lack of focus in these PRs can also make it difficult to ensure that each change is adequately tested and integrated, increasing the risk of regression bugs and integration problems.
Strategies for managing mixed-class PRs
- Break Down PRs: Whenever possible, break down mixed-class PRs into smaller, focused PRs. This makes each PR easier to review and ensures that changes are more manageable.
- Clear Commit Messages: Use clear and descriptive commit messages to separate concerns within a single PR. This helps reviewers understand the purpose and impact of each change.
- Detailed Documentation: Provide detailed documentation and comments explaining the changes, especially for mixed-class PRs. This aids reviewers in understanding the rationale behind the modifications.
- Multiple Reviewers: Involve multiple reviewers with different expertise areas to handle complex, mixed-class PRs. This can help distribute the cognitive load and ensure a more thorough review.
Classifying pull requests into distinct categories significantly enhances the code review process by improving focus, efficiency, and collaboration, while maintaining high code quality. By aiming for focused, single-class PRs, developers can reduce review times and improve the overall quality of the codebase. However, managing mixed-class PRs remains a challenge that requires careful attention to detail and clear communication among development team members.
written and researched with the help of A.I.