debugging

name	debugging
description	Systematic debugging workflow to find and fix bugs efficiently. Use this skill when troubleshooting errors, investigating issues, or when code doesn't work as expected.

🐛 Debugging Skill

Workflow

Step 1: Reproduce 🔄

- [ ] ทำซ้ำปัญหาให้ได้
- [ ] บันทึกขั้นตอนที่ทำให้เกิด error
- [ ] ตรวจสอบ error message/stack trace

Step 2: Isolate 🎯

- [ ] หาไฟล์/function ที่เกี่ยวข้อง
- [ ] ใช้ console.log หรือ debugger
- [ ] ตัด code ออกทีละส่วนจนหาจุดที่พัง

Step 3: Root Cause Analysis 🔬

- [ ] ถาม "ทำไม" 5 ครั้ง (5 Whys)
- [ ] ดู git blame/history
- [ ] ตรวจ dependencies versions

Step 4: Fix 🔧

- [ ] แก้ไขที่ root cause ไม่ใช่ symptom
- [ ] ทำให้ fix เล็กที่สุดเท่าที่จะทำได้
- [ ] ไม่ทำให้อย่างอื่นพัง

Step 5: Verify ✅

- [ ] ทดสอบว่า bug หายแล้ว
- [ ] ทดสอบ edge cases
- [ ] Run existing tests

Step 6: Document 📝

- [ ] บันทึกลง solutions.md
- [ ] บันทึกลง lessons.md (ถ้าเรียนรู้อะไรใหม่)
- [ ] Update changelog

Common Debugging Commands

# Check process
Get-Process | Where-Object { $_.Name -like "*node*" }

# Check ports
netstat -ano | findstr ":3000"

# Kill process
Stop-Process -Name "node" -Force

Decision Tree

Error occurred
├── Has error message? → Google it first
├── Works locally but not in prod? → Check env variables
├── Works yesterday? → Check git diff
└── Random/intermittent? → Check async/race conditions

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🤖 AI-Assisted Debugging

Auto Root Cause Analysis

Error Pattern	Likely Cause	Fix Suggestion
Cannot read property of undefined	Missing null check	Add optional chaining ?.
ECONNREFUSED	Service not running	Start the service
CORS error	Missing headers	Add CORS middleware
Module not found	Missing dependency	npm install
Maximum call stack	Infinite recursion	Check recursion base case

AI Debug Patterns

// Pattern: Add context to errors
try {
  await processData(input);
} catch (error) {
  console.error('processData failed:', {
    input,
    error: error.message,
    stack: error.stack,
    timestamp: new Date().toISOString()
  });
  throw error;
}

Quick Fix Commands

# Clear caches
npm cache clean --force
rm -rf node_modules && npm install

# Reset DB
npx prisma migrate reset

# Check environment
node -e "console.log(process.env)"

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🔧 Auto-Fix Suggestions

Common Fixes

Issue	Auto-Fix
TypeScript errors	Regenerate types
Build failures	Clear build cache
Test failures	Update snapshots
Lock file conflicts	Delete & regenerate

Debug Logging Template

const DEBUG = process.env.DEBUG === 'true';

function log(...args) {
  if (DEBUG) console.log('[DEBUG]', new Date().toISOString(), ...args);
}