Pull Request - Best Practices

1. What is a Pull Request Review?

A pull request review (code review) is the process in which one or more people analyze the code of a PR before it is merged into the main branch of a project. The goal of the review is to ensure that the code is free of errors, understandable, consistent, and well documented.

2. Reasons for a Pull Request Review

• Error detection: The review helps discover errors or logical weaknesses in the code before they enter the main project.
• Improve code quality: The reviewer ensures that the code follows best practices and is well structured.
• Learning opportunities: It is an opportunity for the team to learn from each other and improve their programming skills.
• Ensure consistency: Make sure the code adheres to the project's guidelines and standards.

3. Best Practices for Pull Request Reviews

1. Understand what the Pull Request does

Before starting the review of the code, the context of the PR should be understood: - What is the pull request trying to change or improve? - What problem is it solving? - Are clear goals and instructions given in the PR description?

Reading the description, following the changes, and understanding the underlying problem are essential to provide informed feedback.

2. Review small pull requests

Small pull requests are easier to review and reduce the likelihood of overlooking errors. Ideally, a PR should not exceed 200 to 300 lines of changes, as larger changes are harder to understand.

Tip for developers:

If a PR becomes too large, consider splitting it into several smaller PRs.

3. Step-by-step review

• File by file: Start by reviewing individual files. Check their structure, naming conventions, and whether each file correctly implements the intended functionality.
• Logic and functionality: Verify if the code does what the description says it should.
• Errors and exceptions: Watch out for potential errors, edge cases, or unhandled exceptions.

4. Check for consistency

Consistency is very important in a project. Ensure the PR: - Follows the project's coding guidelines (e.g., naming conventions, formatting). - Has a similar structure to the existing code. - Correctly uses existing functions and data structures rather than creating unnecessary new ones.

5. Code readability and maintainability

The code should be easy to understand and well documented. Check whether: - Variable and function names are clear and descriptive. - The code is divided into logical sections. - Comments are used to explain complex or non-obvious parts.

A good indicator of maintainable code is whether you understand it without long contemplation.

6. Ensure test coverage

An important practice is to ensure the PR is sufficiently tested. This involves: - Unit tests: Each function should have its own tests to ensure it works as expected. - Integration tests: If the PR changes multiple parts of code, integration tests should verify that the components work together correctly. - Edge cases: Check if edge cases are tested, especially boundary values, invalid inputs, or exceptions.

Verify whether the PR includes tests and whether these tests cover all important scenarios.

7. Check automated tests and CI

Many projects use Continuous Integration (CI) to automatically test pull requests. It is important that the PR passes the automated tests before being merged. Make sure all tests in the CI pipeline have passed and no errors remain.

If a test fails: - Review the error messages. - Require the developer to fix the issue before merging the PR.

8. Give constructive feedback

The goal of a pull request review is to improve the code and support the developer. Feedback should always be constructive and helpful. Instead of merely pointing out errors, the reviewer should explain: - Why a certain section is problematic. - Suggestions for improvements. - Highlight positive aspects of the PR to motivate the developer.

Example of constructive feedback:

• Negative: "This is bad."
• Constructive: "This part of the code is hard to understand. Perhaps you could split it into a function and use clearer variable names?"

9. Question assumptions

Sometimes assumptions in the code could lead to future errors. Ask yourself: - Are there assumptions about inputs or edge cases that might cause errors? - Were possible exceptions or invalid inputs considered?

By questioning these assumptions, potential problems can be detected early.

10. Merging pull requests

If the PR passes review and all comments are resolved, it can be merged. Before merging, however, check: - Conflicts: Are there conflicts between the PR and the target branch? These must be resolved before merging. - Test status: Ensure all tests have passed.

Depending on the project, the reviewer may merge the PR themselves or leave it to the author after the review is complete.

4. Typical Mistakes in Pull Request Reviews

1. Too superficial: Not reviewing the code thoroughly enough, resulting in overlooked issues.
2. Too nitpicky: Focusing on unimportant details like formatting errors instead of functionality and structure.
3. Lack of communication: Providing feedback without explaining to the author why certain changes are needed.
4. Insufficient testing: Failing to check whether the code is adequately tested.

5. Summary

Reviewing pull requests is an important process that helps ensure the quality and stability of a project. By carefully reviewing the PR, giving constructive feedback, and ensuring the code is tested, you help ensure that only well-structured and functional code reaches the main branch.

Best practices summarized: - Understand the purpose of the PR. - Focus on small, manageable pull requests. - Check for consistency, readability, and test coverage. - Provide constructive and helpful feedback. - Ensure all automated tests pass.

With these best practices, you can make the code review process more efficient and at the same time improve the code quality of your project.

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