By name: handling-errors description: Prevents silent failures and context loss in error handling. Use when writing try-catch blocks, designing error propagation, reviewing catch blocks, or implementing Result patterns.
Handling Errors
Error Categories
| Type | Examples | Handling |
|---|---|---|
| Expected | Validation, Not found, Unauthorized | Return Result type, log info |
| Transient | Network timeout, Rate limit | Retry with backoff, log warn |
| Unexpected | Null reference, DB crash | Log error, show support ID |
| Critical | Auth down, Payment gateway offline | Circuit breaker, alert |
Fail Fast vs Degrade Gracefully
Fail fast for critical dependencies:
await connectToDatabase(); // Throws on failure - app can't run without it
Degrade gracefully for optional features:
const prefs = await loadPreferences(userId).catch(() => DEFAULT_PREFS);
Log at the Right Layer
// ❌ Logging at every layer = same error 3x
async function fetchData() {
try { return await fetch(url); }
catch (e) { console.error("Fetch failed:", e); throw e; }
}
// ✅ Log once where handled
async function fetchData() {
const response = await fetch(url);
if (!response.ok) throw new Error(`HTTP ${response.status}`);
return response;
}
// Top level logs the error once
Language-Specific Patterns
- TypeScript/React: See references/typescript-react.md for Error Boundaries, typed errors, Result pattern, UI display
- Python: See references/python.md for EAFP, exception chaining, context managers
- Go: See references/go.md for explicit error returns, wrapping with %w, sentinel errors
Anti-Patterns
| Pattern | Problem | Fix |
|---|---|---|
| Empty catch blocks | Hides errors | Log or re-throw |
return false on error |
Loses context | Return Result type |
| Generic "Error" messages | Undebuggable | Include what/why/context |
| Logging same error at each layer | Log pollution | Log once at boundary |
Bare except: / catch (e) all |
Catches system signals | Catch specific types |