Code Review

AI-Powered Code Review Engine

This skill provides comprehensive automated code review with focus on security, performance, maintainability, and test coverage.

🔍 Review Categories

1. Security Analysis

Check for:

• Authentication/authorization vulnerabilities
• SQL injection risks
• XSS (Cross-Site Scripting) vulnerabilities
• Hardcoded secrets or API keys
• Insecure dependencies
• CSRF protection
• Input validation gaps
• Sensitive data exposure

Common Vulnerabilities:

// ❌ SQL Injection risk
const query = `SELECT * FROM users WHERE id = ${userId}`;

// ✅ Use parameterized queries
const query = 'SELECT * FROM users WHERE id = ?';
db.query(query, [userId]);

// ❌ XSS vulnerability
element.innerHTML = userInput;

// ✅ Sanitize input
element.textContent = userInput;
// or use a sanitization library

// ❌ Hardcoded secret
const API_KEY = "sk_live_abc123xyz789";

// ✅ Use environment variables
const API_KEY = process.env.API_KEY;

2. Performance Analysis

Check for:

• N+1 query problems
• Inefficient algorithms (O(n²) when O(n) possible)
• Unnecessary re-renders (React)
• Memory leaks
• Blocking operations
• Large bundle sizes
• Unoptimized images
• Missing caching opportunities

Common Issues:

// ❌ N+1 query problem
for (const user of users) {
  const posts = await db.query('SELECT * FROM posts WHERE user_id = ?', [user.id]);
}

// ✅ Single query with JOIN
const usersWithPosts = await db.query(`
  SELECT users.*, posts.*
  FROM users
  LEFT JOIN posts ON users.id = posts.user_id
`);

// ❌ Unnecessary re-renders
function Component({ data }) {
  const processedData = expensiveOperation(data); // Runs every render
  return <div>{processedData}</div>;
}

// ✅ Memoization
function Component({ data }) {
  const processedData = useMemo(() => expensiveOperation(data), [data]);
  return <div>{processedData}</div>;
}

3. Maintainability Analysis

Check for:

• Code complexity (cyclomatic complexity)
• Long functions (> 50 lines)
• Deeply nested code (> 3 levels)
• Duplicate code
• Unclear variable names
• Missing documentation
• Inconsistent coding style
• God objects/classes

Metrics:

// ❌ High complexity (complexity: 10+)
function processOrder(order) {
  if (order.type === 'standard') {
    if (order.amount > 100) {
      if (order.customer.isPremium) {
        if (order.items.length > 5) {
          // Deep nesting continues...
        }
      }
    }
  }
}

// ✅ Refactored (complexity: 3)
function processOrder(order) {
  if (!isProcessable(order)) {
    return handleInvalidOrder(order);
  }

  const discount = calculateDiscount(order);
  return applyDiscount(order, discount);
}

function isProcessable(order) {
  return order.type === 'standard' && order.amount > 0;
}

4. Test Coverage Analysis

Check for:

• Overall coverage percentage
• Uncovered critical paths
• Missing edge case tests
• Flaky tests
• Slow tests
• Test quality (assertions vs test length)

Coverage Goals:

• Critical code (auth, payment): 95%+
• Business logic: 80%+
• Utilities: 70%+
• UI components: 60%+

📊 Review Output Format

🔍 Code Analysis Results
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

📈 Performance
✅ 3 optimization opportunities found
  - UsersList component: Recommend React.memo (line 45)
  - API call results: Add caching (line 128)
  - Array operations: Parallelize with Promise.all (line 201)

🔒 Security
✅ No critical issues detected
⚠️  1 warning
  - Input validation: Add sanitization for user-generated content (line 89)

🛠️ Maintainability
⚠️ 2 method extractions recommended
  - validateUserInput: Complexity 15 → recommend <10 (line 156)
  - processPaymentData: Length 120 lines → recommend <50 (line 234)

✅ Test Coverage
📊 85% (target: 90%)
  - Add 3 error handling test cases
    - Test invalid email format (auth.test.ts)
    - Test network timeout (api.test.ts)
    - Test concurrent updates (user.test.ts)
  - Add 2 edge case tests
    - Test empty array input (utils.test.ts)
    - Test boundary values (validation.test.ts)

📚 Documentation
⚠️ 2 functions missing proper documentation
  - calculateTotalPrice(): Add JSDoc (line 45)
  - formatUserData(): Missing parameter descriptions (line 123)

━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
Priority: 🔴 1 Critical, 🟡 5 High, 🟢 8 Medium
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

🎯 Automated Checks

Execute during review:

1. Lint errors - Check for code style violations
2. Type safety - Verify TypeScript strict mode compliance
3. Test execution - Ensure all tests pass
4. Code coverage - Check coverage thresholds
5. Security scan - Run security vulnerability checks
6. Performance profiling - Identify slow operations

# Automated checks script
pnpm run lint
pnpm tsc --noEmit
pnpm test -- --coverage
pnpm audit

💡 Suggestion Priority

🔴 Critical (Fix Immediately)

• Security vulnerabilities
• Data loss risks
• Production crashes
• Breaking changes without migration

🟡 High (Fix Before Merge)

• Performance issues (>100ms operations)
• Memory leaks
• Incorrect business logic
• Missing error handling

🟢 Medium (Address Soon)

• Code complexity issues
• Missing documentation
• Test coverage gaps
• Minor performance optimizations

🔵 Low (Nice to Have)

• Style improvements
• Variable naming suggestions
• Additional abstractions
• Micro-optimizations

📋 Review Checklist

Code Quality

• Functions are small and focused (<50 lines)
• Variable names are clear and descriptive
• No magic numbers (use named constants)
• No commented-out code
• Consistent code style
• DRY principle followed

Security

• Input validation implemented
• Output encoding/escaping applied
• Authentication checked for protected routes
• Authorization verified for sensitive operations
• No hardcoded credentials
• Dependencies are up-to-date and secure

Performance

• No N+1 queries
• Efficient algorithms used
• Caching implemented where appropriate
• Database queries optimized
• Lazy loading considered
• No memory leaks

Testing

• Unit tests written for new code
• Edge cases covered
• Integration tests for critical paths
• Tests are fast (<100ms each)
• Tests are deterministic (no flaky tests)
• Mocks used appropriately

Documentation

• Public APIs documented
• Complex logic explained
• README updated if needed
• Examples provided
• Breaking changes noted

🚀 Review Workflow

1. Automated Analysis

# Run automated checks
pnpm run lint
pnpm tsc --noEmit
pnpm test -- --coverage
pnpm audit

# Generate coverage report
pnpm test -- --coverage --coverageReporters=html

# Check bundle size
pnpm run build
pnpm run analyze

2. Manual Review

Focus on:

• Business logic correctness
• Architecture decisions
• API design
• User experience
• Edge cases

3. Provide Feedback

Structure feedback:

## Review Comments

### 🔴 Critical Issues
1. **Security**: SQL injection vulnerability in user search (line 45)
   - Use parameterized queries
   - Add input validation

### 🟡 High Priority
1. **Performance**: N+1 query in getUserPosts (line 123)
   - Recommend eager loading with JOIN
   - Estimated improvement: 80% faster

### 🟢 Suggestions
1. **Maintainability**: Extract validation logic (line 200)
   - Create separate validator function
   - Improves testability

### ✅ Positive Feedback
- Clean error handling implementation
- Good test coverage for new features
- Clear commit messages

🔍 Code Smell Detection

Common Code Smells

Long Method (>50 lines):

// Smell: Method too long
function processOrder(order) {
  // 100+ lines of code
}

// Fix: Extract smaller functions
function processOrder(order) {
  validateOrder(order);
  calculateTotal(order);
  applyDiscounts(order);
  finalizeOrder(order);
}

Large Class (>300 lines):

// Smell: God object
class UserManager {
  // 500+ lines handling everything
}

// Fix: Split responsibilities
class UserAuthenticator { }
class UserProfileManager { }
class UserNotificationService { }

Duplicate Code:

// Smell: Copy-paste code
function calculatePriceA(items) {
  let total = 0;
  for (const item of items) {
    total += item.price * item.quantity;
  }
  return total * 1.1; // tax
}

function calculatePriceB(products) {
  let sum = 0;
  for (const product of products) {
    sum += product.price * product.quantity;
  }
  return sum * 1.1; // tax
}

// Fix: Extract common logic
function calculateSubtotal(items) {
  return items.reduce((sum, item) => sum + item.price * item.quantity, 0);
}

function applyTax(amount) {
  return amount * 1.1;
}

function calculatePrice(items) {
  return applyTax(calculateSubtotal(items));
}

💎 Best Practices

1. Be constructive - Suggest improvements, don't just criticize
2. Explain why - Provide context for suggestions
3. Prioritize issues - Use severity levels
4. Acknowledge good code - Positive feedback is important
5. Ask questions - Seek clarification before assumptions
6. Provide examples - Show better alternatives
7. Be timely - Review promptly
8. Be respectful - Remember there's a person behind the code

🎓 Resources

• OWASP Top 10
• Clean Code Principles
• React Performance Optimization
• TypeScript Best Practices