259 lines
6.5 KiB
Markdown
259 lines
6.5 KiB
Markdown
---
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id: api-openapi-spec
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title: OpenAPI / Swagger — Schema-first vs Code-first
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category: Coding
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status: draft
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source_trust_level: B
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verification_status: conceptual
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created_at: 2026-05-09
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updated_at: 2026-05-09
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tags: [api, openapi, swagger, vibe-coding]
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tech_stack: { language: "TS / OpenAPI", applicable_to: ["Backend"] }
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applied_in: []
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aliases: [OpenAPI, Swagger, schema-first, code-first, Hono RPC, oRPC, ts-rest]
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---
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# OpenAPI
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> API contract 표준. **Schema → Type generation, mock server, client SDK, docs**. Schema-first 또는 Code-first. **Hono / ts-rest / oRPC** 가 modern code-first.
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## 📖 핵심 개념
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- OpenAPI 3.1: 표준 spec.
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- Schema-first: yaml/json 먼저 → 코드 생성.
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- Code-first: 코드의 type → spec 자동.
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- Server / client SDK 자동.
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## 💻 코드 패턴
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### Schema-first (yaml)
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```yaml
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openapi: 3.1.0
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info:
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title: Acme API
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version: 1.0.0
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paths:
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/orders:
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get:
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summary: List orders
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parameters:
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- { name: limit, in: query, schema: { type: integer, default: 20 } }
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- { name: cursor, in: query, schema: { type: string } }
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responses:
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'200':
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description: ok
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content:
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application/json:
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schema:
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$ref: '#/components/schemas/OrderList'
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post:
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summary: Create order
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requestBody:
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required: true
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content:
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application/json:
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schema: { $ref: '#/components/schemas/CreateOrder' }
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responses:
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'201':
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description: created
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content:
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application/json:
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schema: { $ref: '#/components/schemas/Order' }
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'400':
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description: validation error
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content:
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application/problem+json:
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schema: { $ref: '#/components/schemas/Problem' }
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components:
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schemas:
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Order:
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type: object
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required: [id, items, total]
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properties:
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id: { type: string, format: uuid }
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items:
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type: array
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items: { $ref: '#/components/schemas/OrderItem' }
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total: { type: string }
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status: { type: string, enum: [open, paid, shipped] }
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Problem:
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type: object
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required: [type, title, status]
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properties:
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type: { type: string, format: uri }
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title: { type: string }
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status: { type: integer }
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detail: { type: string }
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```
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### 코드 생성
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```bash
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# Server stub
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openapi-generator-cli generate -i api.yaml -g typescript-node-server -o server/
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# Client SDK
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openapi-generator-cli generate -i api.yaml -g typescript-axios -o client/
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# 또는 modern: openapi-typescript
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npx openapi-typescript api.yaml -o api-types.ts
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```
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```ts
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import type { paths } from './api-types';
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type CreateOrderRequest = paths['/orders']['post']['requestBody']['content']['application/json'];
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type OrderResponse = paths['/orders']['post']['responses']['201']['content']['application/json'];
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```
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### Code-first — Hono + zod-openapi
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```ts
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import { OpenAPIHono, createRoute, z } from '@hono/zod-openapi';
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const app = new OpenAPIHono();
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const route = createRoute({
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method: 'post',
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path: '/orders',
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request: {
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body: {
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content: { 'application/json': { schema: CreateOrderSchema } },
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},
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},
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responses: {
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201: {
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content: { 'application/json': { schema: OrderSchema } },
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description: 'Created',
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},
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},
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});
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app.openapi(route, async (c) => {
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const data = c.req.valid('json'); // typed
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const order = await createOrder(data);
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return c.json(order, 201);
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});
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// Spec 노출
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app.doc('/openapi.json', { openapi: '3.1.0', info: { title: 'API', version: '1.0' } });
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```
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### Code-first — ts-rest
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```ts
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import { initContract } from '@ts-rest/core';
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const c = initContract();
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export const contract = c.router({
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createOrder: {
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method: 'POST',
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path: '/orders',
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body: CreateOrderSchema,
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responses: { 201: OrderSchema, 400: ProblemSchema },
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},
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});
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// Server (Express / Fastify / Hono)
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import { initServer } from '@ts-rest/express';
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const router = initServer().router(contract, {
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createOrder: async ({ body }) => ({ status: 201, body: await create(body) }),
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});
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// Client (auto-typed)
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import { initClient } from '@ts-rest/core';
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const api = initClient(contract, { baseUrl: '...' });
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const r = await api.createOrder({ body: { items: [...] } });
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```
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→ Frontend / backend 가 type 공유.
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### Mock server (fast prototyping)
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```bash
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# Prism — OpenAPI mock
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prism mock api.yaml --port 4010
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```
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→ Backend 만들기 전에 frontend 시작.
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### Docs UI
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```ts
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// Swagger UI
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import swaggerUi from 'swagger-ui-express';
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app.use('/docs', swaggerUi.serve, swaggerUi.setup(spec));
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// Scalar (modern, beautiful)
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import { apiReference } from '@scalar/express-api-reference';
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app.use('/docs', apiReference({ spec: { url: '/openapi.json' } }));
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// Stoplight Elements
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```
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### Validation (Hono / Express middleware)
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```ts
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// Express
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import OpenApiValidator from 'express-openapi-validator';
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app.use(OpenApiValidator.middleware({ apiSpec: 'api.yaml' }));
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// 자동 validate body / query / response
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```
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### Lint (Spectral)
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```bash
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npx spectral lint api.yaml
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# 표준 / 일관성 검사
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```
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```yaml
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# .spectral.yml
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rules:
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operation-tag-defined: warn
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operation-success-response: error
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no-unresolved-refs: error
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```
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### Diff (breaking change)
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```bash
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npx oasdiff diff old.yaml new.yaml --breaking-only
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# CI 에서 PR 마다
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```
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### Code-first vs Schema-first
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```
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Schema-first:
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+ Single source of truth
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+ Multi-language (server / client)
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- Sync 어려움 (yaml 과 코드)
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Code-first:
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+ TS type 가 진실
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+ Hot reload
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- 다른 언어 client = generate 필요
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```
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## 🤔 의사결정 기준
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| 상황 | 추천 |
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| TS only fullstack | ts-rest / oRPC / Hono RPC / tRPC |
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| 다양한 client 언어 | Schema-first OpenAPI |
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| Public API | OpenAPI + Scalar docs |
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| Mock first | Schema-first + Prism |
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| Strong type 일급 | Code-first |
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| 빠른 prototype | Code-first |
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## ❌ 안티패턴
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- **Spec 과 코드 drift**: schema-first 의 위험. CI 에서 검증.
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- **모든 endpoint 200 만 명시**: 4xx / 5xx 같이.
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- **Schema 안 example**: 사용자 모름.
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- **Auth 누락 (security scheme)**: 명시.
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- **Generated client 직접 변경**: 다음 generate 시 잃음.
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- **OpenAPI 안 서버 검증**: client 만 — server bypass 가능.
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- **Versioning 없는 spec 변경**: breaking.
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## 🤖 LLM 활용 힌트
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- TS = ts-rest / Hono RPC.
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- 다중 언어 = OpenAPI yaml + generators.
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- Spectral lint + oasdiff CI.
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## 🔗 관련 문서
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- [[API_REST_Best_Practices]]
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- [[API_Versioning_Strategies]]
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- [[TS_Schema_Validation_Comparison]]
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