Silent Failure Review - Error Visibility & Handling

Target: All failures are visible, debuggable, and user-informed.

Silent Failure Risk Levels

Pattern	Risk	Impact
Empty catch block	🔴 Critical	Errors completely hidden
Promise without catch	🔴 Critical	Unhandled rejections
Fire and forget async	🟡 High	Lost error context
Console.log only	🟡 High	No user feedback
Missing Error Boundary	🟡 High	App crash on component error
Excessive optional chaining	🟢 Medium	May mask bugs

Section-Based Loading

Section	File	Focus	Triggers
Detection	references/detection-patterns.md	Regex patterns, search commands	空のcatch, empty catch
Handling	references/error-handling.md	Proper error handling patterns	エラーハンドリング
Boundaries	references/error-boundaries.md	React Error Boundary	Error Boundary

Quick Checklist

Critical (Must Fix)

• No empty catch blocks
• All Promises have error handling (.catch or try-catch)
• No console.log as only error handling
• No swallowed errors in event handlers

High Priority

• Error boundaries around major sections
• Async operations in useEffect have error handling
• API calls have proper error states
• Form submissions handle failures

Best Practices

• Errors logged with context (user id, action, etc.)
• User-facing error messages for failures
• Optional chaining used intentionally, not defensively
• Retry logic for transient failures

Key Principles

Principle	Application
Fail Fast	Make failures visible and immediate
User Feedback	Always inform users of failures
Context Logging	Log with enough info to debug
Graceful Degradation	Fail gracefully, not silently

Detection Commands

# Empty catch blocks
rg "catch\s*\([^)]*\)\s*\{\s*\}" --glob "*.{ts,tsx}"

# Then without catch
rg "\.then\([^)]+\)$" --glob "*.{ts,tsx}"

# Console.log only error handling
rg "catch.*console\.log" --glob "*.{ts,tsx}"

Common Patterns

Empty Catch → Proper Handling

// ❌ Silent failure
try {
  await fetchUserData()
} catch (e) {
  // Nothing here - error disappears
}

// ✅ Proper handling
try {
  await fetchUserData()
} catch (error) {
  logger.error('Failed to fetch user data', { error })
  setError('Unable to load user data. Please try again.')
}

Promise Chain → Error Handling

// ❌ Unhandled rejection
fetchData().then(data => setData(data))

// ✅ With error handling
fetchData()
  .then(data => setData(data))
  .catch(error => {
    logger.error('Failed to fetch data', error)
    setError('Loading failed')
  })

References

Core Principles

• @~/.claude/rules/development/PROGRESSIVE_ENHANCEMENT.md - Graceful degradation

Related Skills

• reviewing-type-safety - Type safety catches some errors at compile time
• generating-tdd-tests - Test error paths

Used by Agents

• silent-failure-reviewer - Primary consumer of this skill