Code Review Patterns

Overview

Code reviews catch bugs before they ship. But reviewing code quality before functionality is backwards.

Core principle: First verify it works, THEN verify it's good.

Violating the letter of this process is violating the spirit of review.

The Iron Law

NO CODE QUALITY REVIEW BEFORE SPEC COMPLIANCE

If you haven't verified the code meets requirements, you cannot review code quality.

Two-Stage Review Process

Stage 1: Spec Compliance Review

Does it do what was asked?

1. Read the Requirements

   • What was requested?
   • What are the acceptance criteria?
   • What are the edge cases?

2. Trace the Implementation

   • Does the code implement each requirement?
   • Are all edge cases handled?
   • Does it match the spec exactly?

3. Test Functionality

   • Run the tests
   • Manual test if needed
   • Verify outputs match expectations

Gate: Only proceed to Stage 2 if Stage 1 passes.

Stage 2: Code Quality Review

Is it well-written?

Review in priority order:

1. Security - Vulnerabilities that could be exploited
2. Correctness - Logic errors, edge cases missed
3. Performance - Unnecessary slowness
4. Maintainability - Hard to understand or modify
5. UX - User experience issues (if UI involved)
6. Accessibility - A11y issues (if UI involved)

Security Review Checklist

Check	Looking For	Example Vulnerability
Input validation	Unvalidated user input	SQL injection, XSS
Authentication	Missing auth checks	Unauthorized access
Authorization	Missing permission checks	Privilege escalation
Secrets	Hardcoded credentials	API key exposure
SQL queries	String concatenation	SQL injection
Output encoding	Unescaped output	XSS attacks
CSRF	Missing tokens	Cross-site request forgery
File handling	Path traversal	Reading arbitrary files

For each security issue found:

- [CRITICAL] SQL injection at `src/api/users.ts:45`
  - Problem: User input concatenated into query
  - Fix: Use parameterized query
  - Code: `db.query(\`SELECT * FROM users WHERE id = ?\`, [userId])`

Quality Review Checklist

Check	Good	Bad
Naming	calculateTotalPrice()	calc(), doStuff()
Functions	Does one thing	Multiple responsibilities
Complexity	Linear flow	Nested conditions
Duplication	DRY where sensible	Copy-paste code
Error handling	Graceful failures	Silent failures
Testability	Injectable dependencies	Global state

Performance Review Checklist

Pattern	Problem	Fix
N+1 queries	Loop with DB call	Batch query
Unnecessary loops	Iterating full list	Early return
Missing cache	Repeated expensive ops	Add caching
Memory leaks	Objects never cleaned	Cleanup on dispose
Sync blocking	Blocking main thread	Async operation

UX Review Checklist (UI Code)

Check	Verify
Loading states	Shows loading indicator
Error states	Shows helpful error message
Empty states	Shows appropriate empty message
Success feedback	Confirms action completed
Form validation	Shows inline errors
Responsive	Works on mobile/tablet

Accessibility Review Checklist (UI Code)

Check	Verify
Semantic HTML	Uses correct elements (button, not div)
Alt text	Images have meaningful alt text
Keyboard	All interactions keyboard accessible
Focus	Focus visible and logical order
Color contrast	Meets WCAG AA (4.5:1 text)
Screen reader	Labels and ARIA where needed

Severity Classification

Severity	Definition	Action
CRITICAL	Security vulnerability or blocks functionality	Must fix before merge
MAJOR	Affects functionality or significant quality issue	Should fix before merge
MINOR	Style issues, small improvements	Can merge, fix later
NIT	Purely stylistic preferences	Optional

Red Flags - STOP and Re-review

If you find yourself:

• Reviewing code style before checking functionality
• Not running the tests
• Skipping the security checklist
• Giving generic feedback ("looks good")
• Not providing file:line citations
• Not explaining WHY something is wrong
• Not providing fix recommendations

STOP. Start over with Stage 1.

Rationalization Prevention

Excuse	Reality
"Tests pass so it's fine"	Tests can miss requirements. Check spec compliance.
"Code looks clean"	Clean code can still be wrong. Verify functionality.
"I trust this developer"	Trust but verify. Everyone makes mistakes.
"It's a small change"	Small changes cause big bugs. Review thoroughly.
"No time for full review"	Bugs take more time than reviews. Do it properly.
"Security is overkill"	One vulnerability can sink the company. Check it.

Output Format

## Code Review: [PR Title/Component]

### Stage 1: Spec Compliance ✅/❌

**Requirements:**
- [x] Requirement 1 - implemented at `file:line`
- [x] Requirement 2 - implemented at `file:line`
- [ ] Requirement 3 - NOT IMPLEMENTED

**Tests:** PASS (24/24)

**Verdict:** [Meets spec / Missing requirements]

---

### Stage 2: Code Quality

**Security:**
- [CRITICAL] Issue at `file:line` - Fix: [recommendation]
- No issues found ✅

**Performance:**
- [MAJOR] N+1 query at `file:line` - Fix: Use batch query
- No issues found ✅

**Quality:**
- [MINOR] Unclear naming at `file:line` - Suggestion: rename to X
- No issues found ✅

**UX/A11y:** (if UI code)
- [MAJOR] Missing loading state - Fix: Add spinner
- No issues found ✅

---

### Summary

**Decision:** Approve / Request Changes

**Critical:** [count]
**Major:** [count]
**Minor:** [count]

**Required fixes before merge:**
1. [Most important fix]
2. [Second fix]

Review Loop Protocol

After requesting changes:

1. Wait for fixes - Developer addresses issues
2. Re-review - Check that fixes actually fix the issues
3. Verify no regressions - Run tests again
4. Approve or request more changes - Repeat if needed

Never approve without verifying fixes work.

Final Check

Before approving:

• Stage 1 complete (spec compliance verified)
• Stage 2 complete (all checklists reviewed)
• All critical/major issues addressed
• Tests pass
• No regressions introduced
• Evidence captured for each claim