Example of Express + Zod + Zod to OpenAPI + Swagger UI

main.ts

import express from 'express';
import morgan from 'morgan';
import swaggerUi from 'swagger-ui-express';
import { extendZodWithOpenApi, OpenApiGeneratorV3, OpenAPIRegistry } from '@asteasolutions/zod-to-openapi';
import { z } from 'zod';

extendZodWithOpenApi(z);

const host = process.env.HOST ?? 'localhost';
const port = process.env.PORT ? Number(process.env.PORT) : 3000;

const app = express();

// parse json request body
app.use(express.json());

// parse urlencoded request body
app.use(express.urlencoded({ extended: true }));

app.use(morgan('dev'));

export const registry = new OpenAPIRegistry();

const UserSchema = z
  .object({
    id: z.string().openapi({ example: '1212121' }),
    name: z.string().openapi({ example: 'John Doe' }),
    age: z.number().openapi({ example: 42 }),
  })
  .openapi('User');

registry.registerPath({
  method: 'get',
  path: '/users/{id}',
  summary: 'Get a single user',
  request: {
    params: z.object({ id: z.string() }),
    headers: z.object({ 'x-api-key': z.string() }),
    query: z.object({ fields: z.string() }),
  },

  responses: {
    200: {
      description: 'Object with user data.',
      content: {
        'application/json': {
          schema: UserSchema,
        },
      },
    },
  },
});

const generator = new OpenApiGeneratorV3(registry.definitions);
const swaggerDocument = generator.generateDocument({
  openapi: '3.0.0',
  info: {
    version: '1.0.0',
    title: 'My API',
    description: 'This is the API',
  },
  servers: [{ url: 'v1' }],
});

app.use('/api-docs', swaggerUi.serve, swaggerUi.setup(swaggerDocument));

app.use('/', (req, res) => {
  res.send('Hello World');
});

app.listen(port, host, () => {
  console.log(`[ ready ] http://${host}:${port}`);
});

package.json

{
  "dependencies": {
    "@asteasolutions/zod-to-openapi": "^6.4.0",
    "express": "~4.18.1",
    "morgan": "^1.10.0",
    "swagger-ui-express": "^5.0.0",
    "zod": "^3.22.4"
  }
}