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TypeScript、Python、Goにわたる堅牢なエラー処理のパターン。型付きエラー、エラー境界、リトライ、サーキットブレーカー、ユーザー向けエラーメッセージをカバーします。
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Basé sur la classification professionnelle SOC
| name | error-handling |
| description | TypeScript、Python、Goにわたる堅牢なエラー処理のパターン。型付きエラー、エラー境界、リトライ、サーキットブレーカー、ユーザー向けエラーメッセージをカバーします。 |
| origin | ECC |
本番アプリケーション向けの一貫した堅牢なエラー処理パターン。
catchブロックは処理、再スロー、またはログのいずれかを行う必要がある// ドメインのエラー階層を定義する
export class AppError extends Error {
constructor(
message: string,
public readonly code: string,
public readonly statusCode: number = 500,
public readonly details?: unknown,
) {
super(message)
this.name = this.constructor.name
// トランスパイルされたES5 JavaScriptでプロトタイプチェーンを正しく維持する。
// 組み込みのErrorクラスを拡張する際に`instanceof`チェック
// （例: `error instanceof NotFoundError`）が正しく動作するために必要。
Object.setPrototypeOf(this, new.target.prototype)
}
}
export class NotFoundError extends AppError {
constructor(resource: string, id: string) {
super(`${resource} not found: ${id}`, 'NOT_FOUND', 404)
}
}
export class ValidationError extends AppError {
constructor(message: string, details: { field: string; message: string }[]) {
super(message, 'VALIDATION_ERROR', 422, details)
}
}
export class UnauthorizedError extends AppError {
constructor(reason = 'Authentication required') {
super(reason, 'UNAUTHORIZED', 401)
}
}
export class RateLimitError extends AppError {
constructor(public readonly retryAfterMs: number) {
super('Rate limit exceeded', 'RATE_LIMITED', 429)
}
}
失敗が想定され一般的な操作（パース、外部呼び出し）向け:
type Result<T, E = AppError> =
| { ok: true; value: T }
| { ok: false; error: E }
function ok<T>(value: T): Result<T> {
return { ok: true, value }
}
function err<E>(error: E): Result<never, E> {
return { ok: false, error }
}
// 使用例
async function fetchUser(id: string): Promise<Result<User>> {
try {
const user = await db.users.findUnique({ where: { id } })
if (!user) return err(new NotFoundError('User', id))
return ok(user)
} catch (e) {
return err(new AppError('Database error', 'DB_ERROR'))
}
}
const result = await fetchUser('abc-123')
if (!result.ok) {
// TypeScriptはここでresult.errorを認識する
logger.error('Failed to fetch user', { error: result.error })
return
}
// TypeScriptはここでresult.valueを認識する
console.log(result.value.email)
import { NextRequest, NextResponse } from 'next/server'
function handleApiError(error: unknown): NextResponse {
// 既知のアプリケーションエラー
if (error instanceof AppError) {
return NextResponse.json(
{
error: {
code: error.code,
message: error.message,
...(error.details ? { details: error.details } : {}),
},
},
{ status: error.statusCode },
)
}
// Zodバリデーションエラー
if (error instanceof z.ZodError) {
return NextResponse.json(
{
error: {
code: 'VALIDATION_ERROR',
message: 'Request validation failed',
details: error.issues.map(i => ({
field: i.path.join('.'),
message: i.message,
})),
},
},
{ status: 422 },
)
}
// 予期しないエラー — 詳細をログに記録し、汎用メッセージを返す
console.error('Unexpected error:', error)
return NextResponse.json(
{ error: { code: 'INTERNAL_ERROR', message: 'An unexpected error occurred' } },
{ status: 500 },
)
}
export async function POST(req: NextRequest) {
try {
// ... ハンドラーロジック
} catch (error) {
return handleApiError(error)
}
}
import { Component, ErrorInfo, ReactNode } from 'react'
interface Props {
fallback: ReactNode
onError?: (error: Error, info: ErrorInfo) => void
children: ReactNode
}
interface State {
hasError: boolean
error: Error | null
}
export class ErrorBoundary extends Component<Props, State> {
state: State = { hasError: false, error: null }
static getDerivedStateFromError(error: Error): State {
return { hasError: true, error }
}
componentDidCatch(error: Error, info: ErrorInfo) {
this.props.onError?.(error, info)
console.error('Unhandled React error:', error, info)
}
render() {
if (this.state.hasError) return this.props.fallback
return this.props.children
}
}
// 使用例
<ErrorBoundary fallback={<p>Something went wrong. Please refresh.</p>}>
<MyComponent />
</ErrorBoundary>
class AppError(Exception):
"""基底アプリケーションエラー。"""
def __init__(self, message: str, code: str, status_code: int = 500):
super().__init__(message)
self.code = code
self.status_code = status_code
class NotFoundError(AppError):
def __init__(self, resource: str, id: str):
super().__init__(f"{resource} not found: {id}", "NOT_FOUND", 404)
class ValidationError(AppError):
def __init__(self, message: str, details: list[dict] | None = None):
super().__init__(message, "VALIDATION_ERROR", 422)
self.details = details or []
from fastapi import FastAPI, Request
from fastapi.responses import JSONResponse
app = FastAPI()
@app.exception_handler(AppError)
async def app_error_handler(request: Request, exc: AppError) -> JSONResponse:
return JSONResponse(
status_code=exc.status_code,
content={"error": {"code": exc.code, "message": str(exc)}},
)
@app.exception_handler(Exception)
async def generic_error_handler(request: Request, exc: Exception) -> JSONResponse:
# 詳細をログに記録し、汎用メッセージを返す
logger.exception("Unexpected error", exc_info=exc)
return JSONResponse(
status_code=500,
content={"error": {"code": "INTERNAL_ERROR", "message": "An unexpected error occurred"}},
)
package domain
import "errors"
// 型チェック用センチネルエラー
var (
ErrNotFound = errors.New("not found")
ErrUnauthorized = errors.New("unauthorized")
ErrConflict = errors.New("conflict")
)
// コンテキスト付きでエラーをラップする — 元のエラーを失わない
func (r *UserRepository) FindByID(ctx context.Context, id string) (*User, error) {
user, err := r.db.QueryRow(ctx, "SELECT * FROM users WHERE id = $1", id)
if errors.Is(err, sql.ErrNoRows) {
return nil, fmt.Errorf("user %s: %w", id, ErrNotFound)
}
if err != nil {
return nil, fmt.Errorf("querying user %s: %w", id, err)
}
return user, nil
}
// ハンドラーレベルでアンラップしてレスポンスを決定する
func (h *Handler) GetUser(w http.ResponseWriter, r *http.Request) {
user, err := h.service.GetUser(r.Context(), chi.URLParam(r, "id"))
if err != nil {
switch {
case errors.Is(err, domain.ErrNotFound):
writeError(w, http.StatusNotFound, "not_found", err.Error())
case errors.Is(err, domain.ErrUnauthorized):
writeError(w, http.StatusForbidden, "forbidden", "Access denied")
default:
slog.Error("unexpected error", "err", err)
writeError(w, http.StatusInternalServerError, "internal_error", "An unexpected error occurred")
}
return
}
writeJSON(w, http.StatusOK, user)
}
interface RetryOptions {
maxAttempts?: number
baseDelayMs?: number
maxDelayMs?: number
retryIf?: (error: unknown) => boolean
}
async function withRetry<T>(
fn: () => Promise<T>,
options: RetryOptions = {},
): Promise<T> {
const {
maxAttempts = 3,
baseDelayMs = 500,
maxDelayMs = 10_000,
retryIf = () => true,
} = options
let lastError: unknown
for (let attempt = 1; attempt <= maxAttempts; attempt++) {
try {
return await fn()
} catch (error) {
lastError = error
if (attempt === maxAttempts || !retryIf(error)) throw error
const jitter = Math.random() * baseDelayMs
const delay = Math.min(baseDelayMs * 2 ** (attempt - 1) + jitter, maxDelayMs)
await new Promise(resolve => setTimeout(resolve, delay))
}
}
throw lastError
}
// 使用例: 一時的なネットワークエラーはリトライ、4xxはリトライしない
const data = await withRetry(() => fetch('/api/data').then(r => r.json()), {
maxAttempts: 3,
retryIf: (error) => !(error instanceof AppError && error.statusCode < 500),
})
エラーコードを人間が読めるメッセージにマッピングする。技術的な詳細はユーザーに見えるテキストに含めない。
const USER_ERROR_MESSAGES: Record<string, string> = {
NOT_FOUND: 'The requested item could not be found.',
UNAUTHORIZED: 'Please sign in to continue.',
FORBIDDEN: "You don't have permission to do that.",
VALIDATION_ERROR: 'Please check your input and try again.',
RATE_LIMITED: 'Too many requests. Please wait a moment and try again.',
INTERNAL_ERROR: 'Something went wrong on our end. Please try again later.',
}
export function getUserMessage(code: string): string {
return USER_ERROR_MESSAGES[code] ?? USER_ERROR_MESSAGES.INTERNAL_ERROR
}
エラー処理に触れるコードをマージする前に:
catchブロックが処理、再スロー、またはログを行っている — サイレントな飲み込みなし{ error: { code, message } }に従っているcodeフィールドを持つ基底AppErrorを継承しているErrorBoundaryでラップされているShare durable, inspectable context and handoffs between Claude, Codex, Hermes, Cursor, OpenCode, and other agents through the local ECC Memory Vault. Use when an agent must save work state, transfer context, resume another agent's task, or search shared project knowledge.
Share durable, inspectable context and handoffs between Claude, Codex, Hermes, Cursor, OpenCode, and other agents through the local ECC Memory Vault. Use when an agent must save work state, transfer context, resume another agent's task, or search shared project knowledge.
Share durable, inspectable context and handoffs between Claude, Codex, Hermes, Cursor, OpenCode, and other agents through the local ECC Memory Vault. Use when an agent must save work state, transfer context, resume another agent's task, or search shared project knowledge.
Use when multiple consumers and providers must evolve an API or event schema without field drift, integration surprises, or one side silently redefining the interface.
Instinct-based learning system that observes sessions via hooks, creates atomic instincts with confidence scoring, and evolves them into skills/commands/agents. v2.1 adds project-scoped instincts to prevent cross-project contamination.
Query live GPU inventory, submit an authenticated Itô fixed-rate RFQ, inspect RFQ or procurement status, and run explicitly gated node qualification through the separately installed canonical CLI. Use when a user asks to find H100/H200 capacity, request a fixed compute rate, check Itô compute status, or validate GPU nodes.