NestJS - Swagger contract first approach sample

Description

Nest framework TypeScript starter repository with NestSwaggerContractFirst middleware.

NestSwaggerContractFirst middleware provides a way to bind your NestJS controllers to your swagger repository. It replaces NestJS router by reading the Swagger specification and routing requests to corresponding methods.

The binding is provided by swagger-tools and rely on x-swagger-router-controller swagger extensions to link with NestJS controllers.

Motivation

This project is motivated by the idea to use contract first approach to develop API with NestJS.

As opposed to code first approach, the goal is to let teams design their API firstly using swagger and then implement it iteratively thanks to stubbing.

This approach ease team communication and in most cases it brings a better API design. It also eases controllers maintenance by removing all boilerplate decorators needed to generate the documentation in code first approach.

You can find other great reasons to adopt contract/design first approach in this article.

How does it works ?

// 1. Load your swagger specification
const swagger = yaml.safeLoad(fs.readFileSync(path.join(__dirname, './swagger/swagger.yaml'), 'utf8'));

const options = {
  swagger,// 2. Provide it in options
  controllers: '**/*.controller.ts',// 3. Indicate where to find your controller classes
  useStubs: true,// You can optionally ask the library to stub missing controllers (usefull if some routes defined in your swagger specification are not yet implemented)
  useSwaggerValidator: true,// You can optionally validates request parameters against specification to handle bad request with ease
  validateResponse: true// You can even validate responses 
}

const app = await NestFactory.create(AppModule);//Bootstrap NestJS application
await registerSwaggerContractFirstMiddleware(app, options);//Register NestSwaggerContractFirst middlewares
await app.listen(3000);//Start the API

registerSwaggerContractFirstMiddleware will first reads options.controllers option to fetch all your controllers. For each of those controllers it will find among exported members the first one that ends up with Controller and will assume this is your controller class object.

Once done it will compute available methods on this object and build a map indexed by controller and method names linking to app controller instance's method (it uses app.get(controllerName) to fetch app controller instance).

Then this map is given to swagger-tools router middleware that route the requests on demand.

It finally uses NestJS RouterResponseController to keep underlying http framework abstraction as much as possible.

Installation

$ yarn

or

$ npm install

Running the app

# development
$ yarn start
# OR
$ npm run start

# watch mode
$ yarn start:dev
# OR
$ npm run start:dev

# production mode
$ yarn start:prod
# OR
$ npm run start:prod

Test

# unit tests
$ yarn test
# OR
$ npm run test

# e2e tests
$ yarn test:e2e
# OR
$ npm run test:e2e

# test coverage
$ yarn test:cov
# OR
$ npm run test:cov

Stay in touch

• Author - Jean-Baptiste WATENBERG

License

This project is MIT licensed.