As someone who writes and reviews a lot of code, I’ve learned pull request (PR) reviews are more than bug checks—they’re about shared ownership, knowledge transfer, and building better code together. Here's a concise, practical guide to make PRs valuable and less painful.
1. Goals of a Good Review
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Focus on improvement, not perfection
Perfect code isn’t realistic—aim for better code. If a PR improves readability, maintainability, or correctness, approve it even if minor style tweaks remain. Use “Nit:” for optional suggestions. google.github.io -
Shared ownership & mentorship
Treat PRs as collective code. Leave educational feedback (“Nit: you could use X here…”), mentor junior devs, and be open to learning from them too.
2. Prep Before Reviewing
- Authors: Self-review: Run tests, linters, and formatters. Provide context in PR descriptions and annotate complex logic.
- Reviewers: Read the description first. Understand the “why” before delving into code.
3. Keep PRs Small & Focused
Data shows review quality drops significantly beyond ~400 LOC and ~60 minutes. atlassian.com devzery.com mikeconley.ca
Guidelines:
- Stay under 200–400 LOC per PR. mikeconley.ca
- Keep reviews under 60 minutes.
- For big features, use stacked PRs (DB → API → UI).
4. Assign Reviewers Thoughtfully
- One primary reviewer, ideally with domain knowledge.
- Max two reviewers, to avoid diffusion of responsibility. support.smartbear.com abseil.io slab.com
- Rotate reviewers for cross-training and healthy bus-factor.
5. What to Check In a PR
Use this mental checklist:
- Correctness: Does it fulfill requirements and handle edge cases?
- Design: Is it well-structured and idiomatic?
- Readability: Clear naming, simple logic, consistent style.
- Security: Validate inputs, sanitize outputs, avoid leaks.
- Performance: Watch out for heavy loops, N+1 queries.
- Tests: Coverage for core, edge, and error cases.
- Compliance: Proper docs, CI, licensing, formatting.
This ensures we catch more issues early—especially maintainability problems. google.github.io developers.google.com google.github.io
6. Leverage Automation
Let tools do the grunt work:
- Linters (ESLint, RuboCop, SonarQube)
- Formatters (Prettier, Black)
- CI pipelines with tests, coverage, security checks
This allows human reviewers to focus on logic, architecture, and nuance.
7. Provide Constructive & Kind Feedback
- Be respectful—punctuate suggestions, not people.
- Praise what’s done well.
- Be actionable: explain why and suggest how.
- Prefix non-blockers with “Nit:” or “Optional:”. atlassian.com google.github.io
- Keep discussions objective (“we” > “you”). Avoid personal critique.
- Suggest synchronous chat if a back-and-forth stalls the process. atlassian.com
8. Measure Process, Not People
Key metrics to track trends (not judge individuals):
- Turnaround time (PR open → merge)
- Inspection rate (< 300–500 LOC/hr best) atlassian.com developers.google.com mikeconley.ca
- Defect density (issues per LOC)
- Review coverage across components
- Follow-up commit count
Use insights to refine your workflow—e.g. emphasize smaller PRs, improve docs, or educate on tricky modules—but never tie metrics to performance reviews. mikeconley.ca google.github.io bssw.io
9. Language-Specific Considerations
Different paradigms require tailored attention:
- PHP/JavaScript/TS: Async handling, XSS, SOLID principles
- Python: Resource management (
with), PEP 8, default-arg pitfalls - Haskell/Scala functional: Type signatures, purity, immutability, macro checks
- C/C++: Memory safety, pointers, RAII
- Java: Null-safety, clean concurrency, SOLID
- Lisp: Macro documentation, dynamic typing, idiomatic patterns
Adapt checklists depending on your stack and involve experts for unfamiliar languages.
Bonus: Recommended Deep-Dive Sources
- Google’s The Standard of Code Review – Philosophy on code health and mentorship. google.github.io
- Google Code Review Developer Guide – Checklist-style guidance. bssw.io
- SmartBear/Cisco study – Empirical findings on PR size and timing. mikeconley.ca
- Atlassian “5 Code Review Best Practices” – Practical style and teamwork tips. atlassian.com
- Blockly PR Flow – Real-world staged review process. developers.google.com
Final Thoughts
PR reviews done right are more than quality gates—they're engines for learning, collaboration, and engineering excellence. By combining respectful culture, smart tooling, data-informed process, and thoughtful feedback, code reviews become rewarding discussions—not chores.
Happy reviewing!
Feel free to drop a comment or reach out if you want to dive deeper or share your own review tips!
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