type-safe-api

Type-Safe API Core Knowledge

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Zod to OpenAPI

Generate OpenAPI specs from Zod schemas for type-first development.

npm install @asteasolutions/zod-to-openapi zod

Define Schemas

import { z } from 'zod';
import { extendZodWithOpenApi } from '@asteasolutions/zod-to-openapi';

extendZodWithOpenApi(z);

// Schema with OpenAPI metadata
export const UserSchema = z.object({
  id: z.string().openapi({ example: 'user_123' }),
  name: z.string().min(1).openapi({ example: 'John Doe' }),
  email: z.string().email().openapi({ example: '[email protected]' }),
  role: z.enum(['user', 'admin']).openapi({ example: 'user' }),
  createdAt: z.date().openapi({ example: '2024-01-01T00:00:00Z' }),
}).openapi('User');

export const CreateUserSchema = UserSchema.omit({ id: true, createdAt: true })
  .openapi('CreateUser');

export type User = z.infer<typeof UserSchema>;
export type CreateUser = z.infer<typeof CreateUserSchema>;

Generate OpenAPI Document

import { OpenAPIRegistry, OpenApiGeneratorV3 } from '@asteasolutions/zod-to-openapi';

const registry = new OpenAPIRegistry();

// Register schemas
registry.register('User', UserSchema);
registry.register('CreateUser', CreateUserSchema);

// Register endpoints
registry.registerPath({
  method: 'get',
  path: '/users/{id}',
  summary: 'Get user by ID',
  request: {
    params: z.object({ id: z.string() }),
  },
  responses: {
    200: {
      description: 'User found',
      content: {
        'application/json': { schema: UserSchema },
      },
    },
    404: {
      description: 'User not found',
    },
  },
});

registry.registerPath({
  method: 'post',
  path: '/users',
  summary: 'Create user',
  request: {
    body: {
      content: {
        'application/json': { schema: CreateUserSchema },
      },
    },
  },
  responses: {
    201: {
      description: 'User created',
      content: {
        'application/json': { schema: UserSchema },
      },
    },
  },
});

// Generate OpenAPI document
const generator = new OpenApiGeneratorV3(registry.definitions);
const openApiDocument = generator.generateDocument({
  openapi: '3.0.0',
  info: {
    title: 'User API',
    version: '1.0.0',
  },
  servers: [{ url: 'https://api.example.com' }],
});