Code Review Checklist

Overview

Provide a systematic checklist for conducting thorough code reviews. This skill helps reviewers ensure code quality, catch bugs, identify security issues, and maintain consistency across the codebase.

When to Use This Skill

•Use when reviewing pull requests
•Use when conducting code audits
•Use when establishing code review standards for a team
•Use when training new developers on code review practices
•Use when you want to ensure nothing is missed in reviews
•Use when creating code review documentation

How It Works

Step 1: Understand the Context

Before reviewing code, I'll help you understand:

•What problem does this code solve?
•What are the requirements?
•What files were changed and why?
•Are there related issues or tickets?
•What's the testing strategy?

Step 2: Review Functionality

Check if the code works correctly:

•Does it solve the stated problem?
•Are edge cases handled?
•Is error handling appropriate?
•Are there any logical errors?
•Does it match the requirements?

Step 3: Review Code Quality

Assess code maintainability:

•Is the code readable and clear?
•Are names descriptive?
•Is it properly structured?
•Are functions/methods focused?
•Is there unnecessary complexity?

Step 4: Review Security

Check for security issues:

•Are inputs validated?
•Is sensitive data protected?
•Are there SQL injection risks?
•Is authentication/authorization correct?
•Are dependencies secure?

Step 5: Review Performance

Look for performance issues:

•Are there unnecessary loops?
•Is database access optimized?
•Are there memory leaks?
•Is caching used appropriately?
•Are there N+1 query problems?

Step 6: Review Tests

Verify test coverage:

•Are there tests for new code?
•Do tests cover edge cases?
•Are tests meaningful?
•Do all tests pass?
•Is test coverage adequate?

Examples

Example 1: Functionality Review Checklist

markdown

## Functionality Review

### Requirements
- [ ] Code solves the stated problem
- [ ] All acceptance criteria are met
- [ ] Edge cases are handled
- [ ] Error cases are handled
- [ ] User input is validated

### Logic
- [ ] No logical errors or bugs
- [ ] Conditions are correct (no off-by-one errors)
- [ ] Loops terminate correctly
- [ ] Recursion has proper base cases
- [ ] State management is correct

### Error Handling
- [ ] Errors are caught appropriately
- [ ] Error messages are clear and helpful
- [ ] Errors don't expose sensitive information
- [ ] Failed operations are rolled back
- [ ] Logging is appropriate

### Example Issues to Catch:

**❌ Bad - Missing validation:**
\`\`\`javascript
function createUser(email, password) {
  // No validation!
  return db.users.create({ email, password });
}
\`\`\`

**✅ Good - Proper validation:**
\`\`\`javascript
function createUser(email, password) {
  if (!email || !isValidEmail(email)) {
    throw new Error('Invalid email address');
  }
  if (!password || password.length < 8) {
    throw new Error('Password must be at least 8 characters');
  }
  return db.users.create({ email, password });
}
\`\`\`

Example 2: Security Review Checklist

markdown

## Security Review

### Input Validation
- [ ] All user inputs are validated
- [ ] SQL injection is prevented (use parameterized queries)
- [ ] XSS is prevented (escape output)
- [ ] CSRF protection is in place
- [ ] File uploads are validated (type, size, content)

### Authentication & Authorization
- [ ] Authentication is required where needed
- [ ] Authorization checks are present
- [ ] Passwords are hashed (never stored plain text)
- [ ] Sessions are managed securely
- [ ] Tokens expire appropriately

### Data Protection
- [ ] Sensitive data is encrypted
- [ ] API keys are not hardcoded
- [ ] Environment variables are used for secrets
- [ ] Personal data follows privacy regulations
- [ ] Database credentials are secure

### Dependencies
- [ ] No known vulnerable dependencies
- [ ] Dependencies are up to date
- [ ] Unnecessary dependencies are removed
- [ ] Dependency versions are pinned

### Example Issues to Catch:

**❌ Bad - SQL injection risk:**
\`\`\`javascript
const query = \`SELECT * FROM users WHERE email = '\${email}'\`;
db.query(query);
\`\`\`

**✅ Good - Parameterized query:**
\`\`\`javascript
const query = 'SELECT * FROM users WHERE email = $1';
db.query(query, [email]);
\`\`\`

**❌ Bad - Hardcoded secret:**
\`\`\`javascript
const API_KEY = 'sk_live_abc123xyz';
\`\`\`

**✅ Good - Environment variable:**
\`\`\`javascript
const API_KEY = process.env.API_KEY;
if (!API_KEY) {
  throw new Error('API_KEY environment variable is required');
}
\`\`\`

Example 3: Code Quality Review Checklist

markdown

## Code Quality Review

### Readability
- [ ] Code is easy to understand
- [ ] Variable names are descriptive
- [ ] Function names explain what they do
- [ ] Complex logic has comments
- [ ] Magic numbers are replaced with constants

### Structure
- [ ] Functions are small and focused
- [ ] Code follows DRY principle (Don't Repeat Yourself)
- [ ] Proper separation of concerns
- [ ] Consistent code style
- [ ] No dead code or commented-out code

### Maintainability
- [ ] Code is modular and reusable
- [ ] Dependencies are minimal
- [ ] Changes are backwards compatible
- [ ] Breaking changes are documented
- [ ] Technical debt is noted

### Example Issues to Catch:

**❌ Bad - Unclear naming:**
\`\`\`javascript
function calc(a, b, c) {
  return a * b + c;
}
\`\`\`

**✅ Good - Descriptive naming:**
\`\`\`javascript
function calculateTotalPrice(quantity, unitPrice, tax) {
  return quantity * unitPrice + tax;
}
\`\`\`

**❌ Bad - Function doing too much:**
\`\`\`javascript
function processOrder(order) {
  // Validate order
  if (!order.items) throw new Error('No items');
  
  // Calculate total
  let total = 0;
  for (let item of order.items) {
    total += item.price * item.quantity;
  }
  
  // Apply discount
  if (order.coupon) {
    total *= 0.9;
  }
  
  // Process payment
  const payment = stripe.charge(total);
  
  // Send email
  sendEmail(order.email, 'Order confirmed');
  
  // Update inventory
  updateInventory(order.items);
  
  return { orderId: order.id, total };
}
\`\`\`

**✅ Good - Separated concerns:**
\`\`\`javascript
function processOrder(order) {
  validateOrder(order);
  const total = calculateOrderTotal(order);
  const payment = processPayment(total);
  sendOrderConfirmation(order.email);
  updateInventory(order.items);
  
  return { orderId: order.id, total };
}
\`\`\`

Best Practices

✅ Do This

•Review Small Changes - Smaller PRs are easier to review thoroughly
•Check Tests First - Verify tests pass and cover new code
•Run the Code - Test it locally when possible
•Ask Questions - Don't assume, ask for clarification
•Be Constructive - Suggest improvements, don't just criticize
•Focus on Important Issues - Don't nitpick minor style issues
•Use Automated Tools - Linters, formatters, security scanners
•Review Documentation - Check if docs are updated
•Consider Performance - Think about scale and efficiency
•Check for Regressions - Ensure existing functionality still works

❌ Don't Do This

•Don't Approve Without Reading - Actually review the code
•Don't Be Vague - Provide specific feedback with examples
•Don't Ignore Security - Security issues are critical
•Don't Skip Tests - Untested code will cause problems
•Don't Be Rude - Be respectful and professional
•Don't Rubber Stamp - Every review should add value
•Don't Review When Tired - You'll miss important issues
•Don't Forget Context - Understand the bigger picture

Complete Review Checklist

Pre-Review

• Read the PR description and linked issues
• Understand what problem is being solved
• Check if tests pass in CI/CD
• Pull the branch and run it locally

Functionality

Security

• No SQL injection vulnerabilities
• No XSS vulnerabilities
• Authentication/authorization is correct
• Sensitive data is protected
• No hardcoded secrets

Performance

Code Quality

• Code is readable and clear
• Names are descriptive
• Functions are focused and small
• No code duplication
• Follows project conventions

Tests

Documentation

• Code comments explain why, not what
• API documentation is updated
• README is updated if needed
• Breaking changes are documented
• Migration guide provided if needed

Git

• Commit messages are clear
• No merge conflicts
• Branch is up to date with main
• No unnecessary files committed
• .gitignore is properly configured

Common Pitfalls

Problem: Missing Edge Cases

Symptoms: Code works for happy path but fails on edge cases Solution: Ask "What if...?" questions

•What if the input is null?
•What if the array is empty?
•What if the user is not authenticated?
•What if the network request fails?

Problem: Security Vulnerabilities

Symptoms: Code exposes security risks Solution: Use security checklist

•Run security scanners (npm audit, Snyk)
•Check OWASP Top 10
•Validate all inputs
•Use parameterized queries
•Never trust user input

Problem: Poor Test Coverage

Symptoms: New code has no tests or inadequate tests Solution: Require tests for all new code

•Unit tests for functions
•Integration tests for features
•Edge case tests
•Error case tests

Problem: Unclear Code

Symptoms: Reviewer can't understand what code does Solution: Request improvements

•Better variable names
•Explanatory comments
•Smaller functions
•Clear structure

Review Comment Templates

Requesting Changes

markdown

**Issue:** [Describe the problem]

**Current code:**
\`\`\`javascript
// Show problematic code
\`\`\`

**Suggested fix:**
\`\`\`javascript
// Show improved code
\`\`\`

**Why:** [Explain why this is better]

Asking Questions

markdown

**Question:** [Your question]

**Context:** [Why you're asking]

**Suggestion:** [If you have one]

Praising Good Code

markdown

**Nice!** [What you liked]

This is great because [explain why]

Related Skills

•@requesting-code-review - Prepare code for review
•@receiving-code-review - Handle review feedback
•@systematic-debugging - Debug issues found in review
•@test-driven-development - Ensure code has tests

Additional Resources

Pro Tip: Use a checklist template for every review to ensure consistency and thoroughness. Customize it for your team's specific needs!