swagger2-koa

Koa 2 async-style middleware for loading, parsing and validating requests via swagger2.

• router(document) => koa2-style Router
• validate(document) => koa2 middleware

Installation

$ npm add swagger2-koa

Usage

router(document) => koa2-style Router

This is the easiest way to use swagger2-koa; it creates a standalone koa server, adds the validate middleware, and returns a Router object that allows you to add your route implementations.

import * as swagger from 'swagger2';
import { router as swaggerRouter, Router } from 'swagger2-koa';

// ...
const document = swagger.loadDocumentSync('./swagger.yml');
const router: Router = swaggerRouter(document);

router.get('/ping', async (context) => {
  context.status = 200;
  context.body = {
    serverTime: new Date().toISOString(),
  };
});

// ...

router
  .app() // get the koa 2 server
  .listen(3000); // start handling requests on port 3000

Note: in addition to validate (described below), router adds the following middleware to its koa server:

• @koa/cors
• @koa/router
• koa-bodyparser

validate(document) => koa2 middleware

If you already have a Koa server, this middleware adds basic loading and validation of HTTP requests and responses against swagger 2.0 document:

import * as swagger from 'swagger2';
import { validate } from 'swagger2-koa';

const app = new Koa();

// load YAML swagger file
const document = swagger.loadDocumentSync('./swagger.yml');

// validate document
if (!swagger.validateDocument(document)) {
  throw Error(`./swagger.yml does not conform to the Swagger 2.0 schema`);
}

app.use(body());
app.use(validate(document));

The validate middleware behaves as follows:

• expects context.body to contain request body in object form (e.g. via use of koa-body)
• if the request is for a path not defined in swagger document, an HTTP 404 is returned to the client (subsequent middleware is never processed).
• if the request body does not validate, an HTTP 400 is returned to the client (subsequent middleware is never processed)
• if the response body does not validate, an HTTP 500 is returned to the client

For either request (HTTP 400) or response (HTTP 500) errors, details of the schema validation error are passed back in the body. e.g.:

{
  "code": "SWAGGER_RESPONSE_VALIDATION_FAILED",
  "errors": [{
     "actual": {"badTime": "mock"},
     "expected": {
        "schema": {"type": "object", "required": ["time"], "properties": {"time": {"type": "string", "format": "date-time"}}}
     },
     "where": "response"
  }]
}

Debugging

This library uses debug, which can be activated using the DEBUG environment variable:

export DEBUG=swagger2-koa:*

Limitations

• only supports Koa 2-style async/await middleware interface
• requires ESM + Node version 22 and above

License

MIT