trpc-openapi

---

OpenAPI support for tRPC 🧩

• Easy REST endpoints for your tRPC procedures.
• Perfect for incremental adoption.
• OpenAPI version 3.0.3.

Usage

1. Install trpc-openapi.

# npm
npm install trpc-openapi@alpha
# yarn
yarn add trpc-openapi@alpha

2. Add OpenApiMeta to your tRPC instance.

import { initTRPC } from '@trpc/server';
import { OpenApiMeta } from 'trpc-openapi';

const t = initTRPC.meta<OpenApiMeta>().create(); /* 👈 */

3. Enable openapi support for a procedure.

export const appRouter = t.router({
  sayHello: t.procedure
    .meta({ /* 👉 */ openapi: { method: 'GET', path: '/say-hello' } })
    .input(z.object({ name: z.string() }))
    .output(z.object({ greeting: z.string() }))
    .query(({ input }) => {
      return { greeting: `Hello ${input.name}!` };
    });
});

4. Generate an OpenAPI document.

import { generateOpenApiDocument } from 'trpc-openapi';

import { appRouter } from '../appRouter';

/* 👇 */
export const openApiDocument = generateOpenApiDocument(appRouter, {
  title: 'tRPC OpenAPI',
  version: '1.0.0',
  baseUrl: 'http://localhost:3000',
});

5. Add an trpc-openapi handler to your app.

We currently support adapters for Express, Next.js & node:http.

Fastify & Serverless soon™, PRs are welcomed 🙌.

import http from 'http';
import { createOpenApiHttpHandler } from 'trpc-openapi';

import { appRouter } from '../appRouter';

const server = http.createServer(createOpenApiHttpHandler({ router: appRouter })); /* 👈 */

server.listen(3000);

6. Profit 🤑

// client.ts
const res = await fetch('http://localhost:3000/say-hello?name=James', { method: 'GET' });
const body = await res.json(); /* { greeting: 'Hello James!' } */

Requirements

Peer dependencies:

• tRPC Server v10 (@trpc/server@next) must be installed.
• Zod v3 (zod@^3.14.4) must be installed.

For a procedure to support OpenAPI the following must be true:

• Both input and output parsers are present AND use Zod validation.
• Query input parsers extend ZodObject<{ [string]: ZodString }> or ZodVoid.
• Mutation input parsers extend ZodObject<{ [string]: ZodAnyType }> or ZodVoid.
• meta.openapi.method is GET, POST, PATCH, PUT or DELETE.
• meta.openapi.path is a string starting with /.
• meta.openapi.path parameters exist in input parser as ZodString

Please note:

• Data transformers are ignored.
• tRPC v9 .interop() routers are not supported.
• Trailing slashes are ignored.
• Routing is case-insensitive.

HTTP Requests

Procedures with a GET/DELETE method will accept inputs via URL query parameters. Procedures with a POST/PATCH/PUT method will accept inputs via the request body with a application/json content type.

Path parameters

A procedure can accept a set of inputs via URL path parameters. You can add a path parameter to any OpenAPI procedure by using curly brackets around an input name as a path segment in the meta.openapi.path field.

Query parameters

Query & path parameter inputs are always accepted as a string, if you wish to support other primitives such as number, boolean, Date etc. please use z.preprocess().

// Router
export const appRouter = t.router({
  sayHello: t.procedure
    .meta({ openapi: { method: 'GET', path: '/say-hello/{name}' /* 👈 */ } })
    .input(z.object({ name: z.string() /* 👈 */, greeting: z.string() }))
    .output(z.object({ greeting: z.string() }))
    .query(({ input }) => {
      return { greeting: `${input.greeting} ${input.name}!` };
    });
});

// Client
const res = await fetch('http://localhost:3000/say-hello/James?greeting=Hello' /* 👈 */, {
  method: 'GET',
});
const body = await res.json(); /* { greeting: 'Hello James!' } */

Request body

// Router
export const appRouter = t.router({
  sayHello: t.procedure
    .meta({ openapi: { method: 'POST', path: '/say-hello/{name}' /* 👈 */ } })
    .input(z.object({ name: z.string() /* 👈 */, greeting: z.string() }))
    .output(z.object({ greeting: z.string() }))
    .mutation(({ input }) => {
      return { greeting: `${input.greeting} ${input.name}!` };
    });
});

// Client
const res = await fetch('http://localhost:3000/say-hello/James' /* 👈 */, {
  method: 'POST',
  headers: { 'Content-Type': 'application/json' },
  body: JSON.stringify({ greeting: 'Hello' }),
});
const body = await res.json(); /* { greeting: 'Hello James!' } */

Custom headers

Any custom headers can be specified in the meta.openapi.headers array, these headers will not be validated on request. Please consider using Authorization for first-class OpenAPI auth/security support.

HTTP Responses

Status codes will be 200 by default for any successful requests. In the case of an error, the status code will be derived from the thrown TRPCError or fallback to 500.

You can modify the status code or headers for any response using the responseMeta function.

Please see error status codes here.

Authorization

To create protected endpoints, add protect: true to the meta.openapi object of each tRPC procedure. You can then authenticate each request with the createContext function using the Authorization header with the Bearer scheme.

Explore a complete example here.

Server

import * as trpc from '@trpc/server';
import { OpenApiMeta } from 'trpc-openapi';

type User = { id: string; name: string };

const users: User[] = [
  {
    id: 'usr_123',
    name: 'James',
  },
];

export type Context = { user: User | null };

const t = initTRPC.context<Context>().meta<OpenApiMeta>().create();

export const createContext = async ({ req, res }): Promise<Context> => {
  let user: User | null = null;
  if (req.headers.authorization) {
    const userId = req.headers.authorization.split(' ')[1];
    user = users.find((_user) => _user.id === userId);
  }
  return { user };
};

export const appRouter = t.router({
  sayHello: t.procedure
    .meta({ openapi: { method: 'GET', path: '/say-hello', protect: true /* 👈 */ } })
    .input(z.void()) // no input expected
    .output(z.object({ greeting: z.string() }))
    .query(({ input, ctx }) => {
      if (!ctx.user) {
        throw new trpc.TRPCError({ message: 'User not found', code: 'UNAUTHORIZED' });
      }
      return { greeting: `Hello ${ctx.user.name}!` };
    }),
});

Client

const res = await fetch('http://localhost:3000/say-hello', {
  method: 'GET',
  headers: { Authorization: 'Bearer usr_123' } /* 👈 */,
});
const body = await res.json(); /* { greeting: 'Hello James!' } */

Examples

For advanced use-cases, please find examples in our complete test suite.

With Express

Please see full example here.

import { createExpressMiddleware } from '@trpc/server/adapters/express';
import express from 'express';
import { createOpenApiExpressMiddleware } from 'trpc-openapi';

import { appRouter } from '../appRouter';

const app = express();

app.use('/api/trpc', createExpressMiddleware({ router: appRouter }));
app.use('/api', createOpenApiExpressMiddleware({ router: appRouter })); /* 👈 */

app.listen(3000);

With Next.js

Please see full example here.

// pages/api/[...trpc].ts
import { createOpenApiNextHandler } from 'trpc-openapi';

import { appRouter } from '../../server/appRouter';

export default createOpenApiNextHandler({ router: appRouter });

With AWS Lambda

Please see full example here.

import { createOpenApiAwsLambdaHandler } from 'trpc-openapi';

import { appRouter } from './appRouter';

export const openApi = createOpenApiAwsLambdaHandler({ router: appRouter });

Types

GenerateOpenApiDocumentOptions

Please see full typings here.

Property	Type	Description	Required
title	string	The title of the API.	true
description	string	A short description of the API.	false
version	string	The version of the OpenAPI document.	true
baseUrl	string	The base URL of the target server.	true
docsUrl	string	A URL to any external documentation.	false
tags	string[]	A list for ordering endpoint groups.	false

OpenApiMeta

Please see full typings here.

Property	Type	Description	Required	Default
enabled	boolean	Exposes this procedure to trpc-openapi adapters and on the OpenAPI document.	false	true
method	HttpMethod	HTTP method this endpoint is exposed on. Value can be GET, POST, PATCH, PUT or DELETE.	true	undefined
path	string	Pathname this endpoint is exposed on. Value must start with /, specify path parameters using {}.	true	undefined
protect	boolean	Requires this endpoint to use an Authorization header credential with Bearer scheme on OpenAPI document.	false	false
summary	string	A short summary of the endpoint included in the OpenAPI document.	false	undefined
description	string	A verbose description of the endpoint included in the OpenAPI document.	false	undefined
tags	string[]	A list of tags used for logical grouping of endpoints in the OpenAPI document.	false	undefined
headers	ParameterObject[]	An array of custom headers to add for this endpoint in the OpenAPI document.	false	undefined

CreateOpenApiNodeHttpHandlerOptions

Please see full typings here.

Property	Type	Description	Required
router	Router	Your application tRPC router.	true
createContext	Function	Passes contextual (ctx) data to procedure resolvers.	false
responseMeta	Function	Returns any modifications to statusCode & headers.	false
onError	Function	Called if error occurs inside handler.	false
maxBodySize	number	Maximum request body size in bytes (default: 100kb).	false

---

Still using tRPC v9? See our master branch.

License

Distributed under the MIT License. See LICENSE for more information.

Contact

James Berry - Follow me on Twitter @jlalmes 💚