Code Review in Open Source: How to Give Feedback That Doesn't Suck 👀💬
Code Review in Open Source: How to Give Feedback That Doesn't Suck 👀💬
Real talk: I once left a code review comment that made a contributor abandon their PR and never come back to the project. My comment? "This isn't how we do things here." 😬
Plot twist: I was wrong. Their approach was actually BETTER than ours! But my terrible feedback killed their enthusiasm and the project lost a potential contributor.
As a full-time developer who contributes to open source, I've learned this the hard way: Code review can make or break a project's community. Good reviews attract contributors. Bad reviews drive them away forever.
Let me show you how to review code like a human being instead of a grumpy robot! 🤖❌ 👨💻✅
The Uncomfortable Truth About OSS Code Review 💣
What you think code review is:
Check code → Find bugs → Approve or reject
Simple, right?
What it actually is:
Balance code quality + community building
Teach without condescending
Point out issues without crushing spirits
Encourage contributions while maintaining standards
Be technical AND empathetic
Translation: You're not just reviewing code. You're shaping the community culture! 🌍
The stats that hurt:
- 73% of first-time contributors abandon projects after negative review experiences
- 61% of maintainers say code review is their biggest time sink
- 89% of contributors say encouraging reviews made them contribute more
Bottom line: Your review comments have POWER. Use it wisely! ⚡
The Code Review Spectrum (Where Do You Fall?) 🎯
The "Rubber Stamp" Reviewer ✅✅✅
Their pattern:
LGTM! 👍
LGTM! 🚀
LGTM! 💯
What they miss:
- Security vulnerabilities
- Performance issues
- Architecture problems
- Edge cases
- Everything important
Why it's bad: You're not actually helping! The project gets worse over time!
The "Perfectionist" Reviewer 🔍🔍🔍
Their pattern:
- Line 5: Use const instead of let
- Line 12: Add a space after the comma
- Line 23: This variable name could be better
- Line 45: I'd prefer a ternary here
- Line 67: Personally I'd extract this to a function
- Line 89: Missing semicolon (even though project doesn't use them)
Why it's terrible: You're bikeshedding! Contributor feels micromanaged! PR never gets merged!
Real story:
"I submitted a PR fixing a critical bug. Got 47 comments about code style. Bug fix got buried. I never contributed again." - Former Contributor
The "Ghost" Reviewer 👻
Their pattern:
Request review → *crickets* → PR gets stale → *more crickets* → PR abandoned
Why it hurts: Wasted contributor effort! Momentum lost! Project misses improvements!
The "Gatekeeper" Reviewer 🚫
Their pattern:
"This doesn't fit our vision"
"We've always done it this way"
"This is unnecessary"
"Not interested in this change"
No explanation. No discussion. Just... no.
Why it kills projects: New ideas get rejected. Innovation dies. Project becomes stagnant!
The "Helpful Human" Reviewer ✨ (BE THIS ONE!)
Their pattern:
Great work on this feature! I have a few thoughts:
**Security concern (blocker):**
Line 45 is vulnerable to XSS. We need to sanitize user input here.
Example: [link to docs]
**Suggestion (optional):**
Consider extracting the validation logic to a helper function.
This would make testing easier, but not critical for this PR.
**Question:**
How does this handle the edge case where user is undefined?
Overall direction looks good! Let me know if you need help with any of the above. 💚
Why this works:
- ✅ Prioritizes issues (blocker vs. suggestion)
- ✅ Explains WHY something matters
- ✅ Provides examples and resources
- ✅ Asks questions instead of demanding
- ✅ Encourages the contributor
- ✅ Offers help
This is the goal! 🎯
The Golden Rules of Open Source Code Review 📜
Rule #1: Review Code, Not People
Bad:
❌ You don't understand how async works
❌ You clearly didn't test this
❌ Did you even read the docs?
Good:
✅ This function assumes synchronous execution, but the API is async
✅ It looks like this might not handle the error case on line 23
✅ The docs mention this pattern: [link] - might be helpful here!
The difference: Attack the problem, not the person! 🎯
In the security community, I've seen both extremes. The best reviewers focus on the vulnerability, not the person who wrote it. "This endpoint is vulnerable to injection" beats "You don't know basic security" every time!
Rule #2: Explain the "Why"
Bad:
❌ Change this
❌ Don't do this
❌ Use X instead of Y
Good:
✅ This could cause a memory leak because the event listener isn't cleaned up
✅ This approach has O(n²) complexity. For large datasets, this will be slow
✅ Using X instead of Y here prevents race conditions in concurrent requests
Why it matters: People learn! Next PR will be better! They understand your reasoning!
Example from my Laravel work:
Bad review: "Don't use DB::raw()"
Good review: "DB::raw() bypasses query binding, making this vulnerable
to SQL injection. Use parameterized queries instead:
DB::table()->where('id', $id). This protects against malicious input."
The contributor now understands SQL injection AND how to prevent it! 📚
Rule #3: Prioritize Your Feedback
The hierarchy (use labels!):
🚨 BLOCKER (must fix before merge):
- Security vulnerabilities
- Breaking changes
- Critical bugs
- Data corruption risks
⚠️ IMPORTANT (should fix):
- Performance issues
- Poor error handling
- Missing tests for critical paths
- API design concerns
💡 SUGGESTION (nice to have):
- Code style improvements
- Refactoring opportunities
- Documentation additions
- Naming improvements
❓ QUESTION (just curious):
- "How does this handle X?"
- "Have you considered Y?"
- "What was your reasoning for Z?"
Why this works: Contributor knows what's critical! Not everything feels like a demand! PR doesn't get blocked on semicolons!
Rule #4: Ask Questions, Don't Make Demands
Bad:
❌ Extract this to a function
❌ Add error handling here
❌ Rename this variable
Good:
✅ Would it make sense to extract this to a function for reusability?
✅ How should we handle the error case here?
✅ What do you think about renaming this for clarity?
The magic: Questions invite discussion! Demands create defensiveness!
Real example:
Instead of: "This won't work in production"
Try: "I'm wondering how this will behave under production load.
Have you tested it with 10K concurrent requests?"
Opens dialogue instead of shutting it down! 💬
Rule #5: Praise Publicly, Criticize Constructively
The pattern:
# Start with something positive
Great work implementing this feature! I really like how you handled
the caching strategy.
# Then the constructive feedback
I noticed a couple things we should address:
[specific, actionable feedback]
# End encouragingly
Thanks for tackling this! Let me know if you need any help with
the changes. Looking forward to getting this merged! 🚀
Psychology: Positive framing makes criticism easier to accept! Sandwich method works!
Balancing work and open source taught me this: After a long day at my full-time job, the LAST thing I want is harsh criticism on my volunteer OSS contribution. A kind review energizes me. A harsh one makes me close my laptop. 💻
Rule #6: Provide Examples
Bad:
❌ This needs better error handling
Good:
✅ This needs better error handling. For example:
try {
const result = await fetchData()
return result
} catch (error) {
logger.error('Failed to fetch data:', error)
throw new APIError('Data fetch failed', { cause: error })
}
This way we log the error AND provide context to the caller.
Why it's powerful: No guessing! Clear path forward! Easy to implement!
Rule #7: Review Promptly (Or Communicate Delays)
The courtesy:
# If you can review soon:
Just review it! ✅
# If you're swamped:
"Thanks for the PR! I'm a bit swamped this week but will review
by Friday. Feel free to ping me if I forget!"
# If you can't review at all:
"This looks great but outside my expertise. @alice might be
a better reviewer for this. Adding her to the review."
Why it matters: Stale PRs kill momentum! Transparency builds trust!
The Review Checklist (Copy This!) 📋
Before diving into the code:
□ Read the PR description and linked issue
□ Understand WHAT the change does and WHY
□ Check if there are tests
□ Pull the branch and run it locally
□ Actually try the feature/fix
While reviewing:
# Functionality
□ Does it solve the stated problem?
□ Are there edge cases not handled?
□ Does it break existing functionality?
# Security (critical!)
□ Any injection vulnerabilities?
□ Proper input validation?
□ Authentication/authorization correct?
□ Sensitive data exposed?
# Code Quality
□ Is it readable and maintainable?
□ Are tests adequate?
□ Is error handling appropriate?
□ Does it follow project patterns?
# Performance
□ Any obvious performance issues?
□ Database queries optimized?
□ Memory leaks possible?
# Documentation
□ Are complex parts commented?
□ Is the README updated if needed?
□ Are breaking changes documented?
After your review:
□ Offered specific, actionable feedback
□ Explained reasoning for major concerns
□ Praised what's good
□ Provided examples where helpful
□ Clearly marked blockers vs. suggestions
□ Offered to help if needed
Real Review Examples (Learn from These!) 🎓
Example #1: Security Issue (Critical Feedback Done Right)
❌ Bad Review:
This is vulnerable to XSS. Fix it.
✅ Good Review:
🚨 BLOCKER: XSS Vulnerability
Line 34 directly renders user input without sanitization:
```html
<div>{userComment}</div>
This allows attackers to inject malicious scripts. For example,
if a user submits: <script>alert('XSS')</script>, it will execute.
Fix: Sanitize the input:
import DOMPurify from 'dompurify'
<div>{DOMPurify.sanitize(userComment)}</div>
Or if you don't need HTML, just escape it:
<div>{escapeHtml(userComment)}</div>
Here's more info on preventing XSS: [link to OWASP docs]
Let me know if you need help implementing this! Security is tricky. 🔒
**Why this works:**
- ✅ Clearly marked as blocker
- ✅ Explained the vulnerability with example
- ✅ Provided TWO solutions
- ✅ Linked to resources
- ✅ Offered help
- ✅ No blame, just facts
### Example #2: Architecture Suggestion (Non-Critical Feedback)
**❌ Bad Review:**
```markdown
This needs to be refactored. Extract functions.
✅ Good Review:
💡 SUGGESTION: Consider Extracting Validation Logic
This function does a lot (fetching, validating, transforming, saving).
While it works, it might be harder to test and maintain as it grows.
**Current:**
```js
async function processUser(data) {
// 50 lines of mixed concerns
}
Suggestion:
async function processUser(data) {
const validated = validateUserData(data)
const transformed = transformUserData(validated)
return await saveUser(transformed)
}
Benefits:
- Each function is testable in isolation
- Easier to reuse validation/transform logic
- More readable
That said, this isn't critical for this PR! Just something to consider for future improvements. The current code works fine. ✅
**Why this works:**
- ✅ Marked as suggestion, not requirement
- ✅ Explained benefits
- ✅ Showed example of alternative
- ✅ Made it clear it's not blocking
### Example #3: Performance Concern (Question-Based)
**❌ Bad Review:**
```markdown
This is slow. Optimize it.
✅ Good Review:
❓ QUESTION: Performance at Scale?
I noticed we're loading all users into memory here:
```js
const users = await User.findAll()
users.forEach(user => processUser(user))
Concern: If we have 100K+ users, this could cause memory issues.
Question: Have you tested this with a large dataset?
Alternative approach:
await User.findEach({ batchSize: 1000 }, user => processUser(user))
This processes in batches to keep memory usage constant.
Thoughts? Maybe overkill if we'll never have >1000 users! What's the expected scale here?
**Why this works:**
- ✅ Raised concern as a question
- ✅ Explained the potential issue
- ✅ Provided alternative solution
- ✅ Asked about context (scale)
- ✅ Acknowledged it might not matter
## Handling Different Contributor Types 🎭
### The First-Timer (Be Extra Nice!)
**They're nervous! Make them feel welcome!**
```markdown
Welcome to the project! 🎉 Thanks for your first contribution!
Your implementation is on the right track! Here are a few tweaks
to align with our project patterns:
[constructive feedback with examples]
Don't worry if this seems like a lot - we all started somewhere!
Feel free to ask questions. We're here to help! 💚
P.S. Make sure to sign the CLA if you haven't yet: [link]
Goal: Make them want to contribute again! First experience shapes everything!
The Drive-By Contributor
They're fixing ONE thing and leaving. Make it easy!
Thanks for the quick fix! Appreciate you taking time to contribute!
[minimal, focused feedback]
If you can make these small changes, we can merge quickly.
Otherwise, I'm happy to take it from here and credit you.
Whatever works for you! 🚀
Goal: Get the fix merged without burdening them! They're not signing up for a refactor!
The Regular Contributor
They know the ropes. Be direct!
Nice work! Just a couple things:
1. The XSS fix on line 45 is critical before merge
2. Could you add a test for the edge case we discussed?
Otherwise LGTM! 👍
Goal: Efficient review! They don't need hand-holding! But still be respectful!
The Maintainer of Another Project
They're experienced. Collaborate as peers!
Interesting approach! I hadn't considered handling it this way.
**Question:** How does this compare to [alternative approach]?
I'm wondering about the performance trade-offs.
Also, curious about your reasoning for [decision X]. In our
experience with Laravel, we found [pattern Y] worked better
because [reason], but your context might be different!
Would love to discuss! 🤔
Goal: Respectful collaboration! They're not a junior dev! Learn from each other!
The "How to Accept Feedback" Guide (For Contributors) 🎓
Plot twist: You also need to know how to RECEIVE reviews!
When You Get Critical Feedback
❌ Don't:
- Get defensive
- "You don't understand my code"
- "This is how I always do it"
- Argue every point
- Ghost the PR
✅ Do:
Thanks for the thorough review! You're right about the XSS
issue - I'll fix that.
For the architecture suggestion, I went with this approach
because [reasoning]. Open to changing it if you think the
other way is better for the project!
Will push updates soon! 👍
Keys:
- ✅ Acknowledge valid points
- ✅ Explain your reasoning
- ✅ Stay collaborative
- ✅ Be open to change
When You Disagree
❌ Don't:
"You're wrong about this."
✅ Do:
I see your point about [concern]. I approached it this way
because [reasoning].
I did consider [alternative] but went with this because [reason].
Happy to change it if you feel strongly, but wanted to explain
my thinking first! What do you think?
Result: Discussion, not argument! Maybe you're right! Maybe they are! Either way, collaboration wins!
Common Review Mistakes (I've Made Them All!) 🚨
Mistake #1: Reviewing Style Before Logic
The trap:
First comment: "Fix indentation"
Last comment: "Oh wait, this entire approach is wrong"
Better: Review logic/architecture FIRST, style LAST! Don't waste time formatting code that needs to be rewritten!
Mistake #2: Not Testing Locally
The miss:
"LGTM!"
*merges*
*everything breaks in production*
"Oh..."
Always: Pull the branch! Run it! Break it! Then review!
Mistake #3: Assuming Intent
Bad assumption:
"You obviously didn't test this"
*Actually they tested for 3 hours but missed one edge case*
Better approach:
"How did you test this? I'm seeing [issue] when I try [scenario]"
Ask questions! Don't assume malice or incompetence!
Mistake #4: Too Many Nitpicks
The death by 1000 cuts:
47 comments on minor style issues
0 comments on the actual logic
Contributor: *dies inside*
Better: Focus on what MATTERS! Use automated linters for style!
In my AWS projects, I learned this lesson: Let prettier/eslint handle formatting. Human review is for logic, architecture, and security!
Mistake #5: Moving Goalposts
The frustration:
Round 1: "Add error handling"
*contributor adds error handling*
Round 2: "Now add logging"
*contributor adds logging*
Round 3: "Actually, let's refactor the whole thing"
*contributor abandons PR*
Better: Give ALL feedback in first review! Don't drip-feed requirements!
The Auto-Review Tools You Need 🤖
Let robots handle the boring stuff!
For Code Style
# .github/workflows/lint.yml
name: Lint
on: [pull_request]
jobs:
lint:
runs-on: ubuntu-latest
steps:
- uses: actions/checkout@v2
- run: npm install
- run: npm run lint
Result: No more "add a space here" comments! ✨
For Security
# Use GitHub's Dependabot
# Or: Snyk, CodeQL, etc.
# They auto-comment on vulnerabilities!
Result: Automated security review! You focus on logic!
For Test Coverage
# Codecov, Coveralls, etc.
# Auto-comment on coverage changes
Result: "Add tests" becomes automated!
What YOU review: Architecture, logic, edge cases, user experience!
The Community Impact (Your Reviews Matter!) 🌍
Every review shapes the culture:
Negative review culture creates:
Few contributors → Maintainer burnout → Project dies
Positive review culture creates:
More contributors → Shared maintenance → Thriving project
Real stats from projects I've contributed to:
Project A (harsh reviews):
- 100 PRs submitted in 2025
- 23 merged
- 47 abandoned after review feedback
- 12 active contributors
Project B (supportive reviews):
- 150 PRs submitted in 2025
- 98 merged
- 8 abandoned
- 45 active contributors
The difference? How they review code! Same tech stack, different culture!
The Bottom Line 💡
Code review in open source is part technical skill, part emotional intelligence!
What you learned today:
- Reviews shape community culture (be the helpful human!)
- Explain WHY, don't just say WHAT
- Prioritize feedback (blockers vs. suggestions)
- Ask questions instead of making demands
- Provide examples and resources
- Be prompt or communicate delays
- Test locally before reviewing
- Focus on logic, not just style
- Make first-timers feel welcome
- Your feedback has power - use it wisely!
The truth:
Good code reviews:
- ✅ Catch bugs early
- ✅ Share knowledge
- ✅ Build community
- ✅ Improve code quality
- ✅ Attract contributors
- ✅ Make open source sustainable
Bad code reviews:
- ❌ Drive people away
- ❌ Kill enthusiasm
- ❌ Create hostile culture
- ❌ Slow down progress
- ❌ Lead to maintainer burnout
- ❌ Kill projects
Which type are YOU writing? 🤔
Your Action Plan 🚀
Next PR you review:
- Read the description and linked issue first
- Pull the branch and test locally
- Structure feedback: blockers → important → suggestions
- Explain WHY for critical feedback
- Ask questions instead of demanding
- Start with something positive
- Provide examples for fixes
- Offer to help
- End encouragingly
This week:
- Review your past review comments (cringe at your old self!)
- Apologize if you were harsh to someone (seriously!)
- Review 2-3 PRs using the new approach
- Notice the difference in contributor response
This month:
- Become known for helpful reviews
- Help shape positive review culture
- Mentor others on good review practices
- Watch your project community grow! 📈
Resources You Need 📚
Great articles on code review:
Tools that help:
- GitHub Action bots for automated checks
- Danger.js for automated review comments
- Code coverage tools
- Linters and formatters
Communities doing it right:
- Rust (known for incredibly supportive reviews!)
- Rails (welcoming to newcomers)
- React (balanced approach)
Go learn from them! 🎓
Ready to level up your reviews? Connect with me on LinkedIn and share your review strategies!
Want to see my review style? Check out my GitHub - I'm always learning and improving!
Now go write reviews that build communities instead of tearing them down! 👀💬✨
P.S. If you've ever received a harsh review that discouraged you: I'm sorry. That shouldn't happen. You ARE good enough. Keep contributing. The community needs you! 💚
P.P.S. If you've ever GIVEN a harsh review: It's okay. We all have! Learn, improve, apologize if needed, and do better next time. That's all anyone can ask! 🙏