npm install --save nest-openapi-tools @nestjs/swagger swagger-ui-express

This library's goal is to make it as easy as possible to use NestJS with Swagger, also known as OpenAPI. NestJS's Swagger package does not currently generate specification file - rather, it generates the web server with the specification.

This package leverages that tooling to generate a YAML or JSON specification file as well as @openapitools/openapi-generator-cli to then generate a client. By using this as part of our development experience, we can build our APIs with NestJS's npm run start:dev running and have a new, fully-setup API client ready to go for our consuming layer (whether this is a SPA app or another API service).

The NestJS OpenAPI docs for @NestJS/Swagger are a fantastic guide to defining your API in code. There are two routes:

1. Using the CLI Plugin. This is recommended as it is very hands-off and easy-to-use. However, it is a bit of a "magic" solution - this can sometimes prove frustrating.
2. Use decorators for operations and types. This is more hands-on but is concise in what is expected to be produced.

These must be complete in order for Nest OpenAPI Tools to function - this package leverages the NestJS Swagger library to generate the server and specification file.

The OpenApiNestFactory simplifies the process of:

1. Generating an OpenAPI file from a NestJS API.
2. Generating a client project (i.e. an Axios client or an Angular client module).
3. Starting up the OpenAPI documentation web server.

To leverage this functionality, add a call to OpenApiNestFactory.configure() call as demonstrated below.

// main.ts - BEFORE
import { NestFactory } from '@nestjs/core';
import { AppModule } from './app.module';

async function bootstrap() {
  const app = await NestFactory.create(AppModule);
  await app.listen(3000);
}
bootstrap();

// main.ts - AFTER
import { NestFactory } from '@nestjs/core';
import { AppModule } from './app.module';
import { OpenApiNestFactory } from 'nest-openapi-tools';

async function bootstrap() {
  const app = await NestFactory.create(AppModule);

  await OpenApiNestFactory.configure(
    app, 
    new DocumentBuilder().setTitle('My API'),
  );

  await app.listen(3000);
}
bootstrap();

This falls back to all defaults provided by Nest OpenAPI Tools to:

• enable the documentation web server at http://localhost:3000/api-docs
• generate the OpenAPI document at ./openapi.yaml
• generate a TypeScript Axios HTTP client at ../my-api-client.

Note that all of these values can be changed as demonstrated in the section below.

These are the default values when no options are passed in to OpenApiNestFactory. To override these, simply use the configuration object (the third argument in the configure() call).

// main.ts
import { NestFactory } from '@nestjs/core';
import { AppModule } from './app.module';
import { OpenApiNestFactory } from 'nest-openapi-tools';

async function bootstrap() {
  const app = await NestFactory.create(AppModule);

  await OpenApiNestFactory.configure(app, 
    new DocumentBuilder()
      .setTitle('My API')
      .setDescription('An API to do awesome things')
      .addBearerAuth(),
    {
      webServerOptions: {
        enabled: true,
        path: 'api-docs',
      },
      fileGeneratorOptions: {
        enabled: true,
        outputFilePath: './openapi.yaml',  // or ./openapi.json
      },
      clientGeneratorOptions: {
        enabled: true,
        type: 'typescript-axios',
        outputFolderPath: '../typescript-api-client/src',
        additionalProperties:
          'apiPackage=clients,modelPackage=models,withoutPrefixEnums=true,withSeparateModelsAndApi=true',
        openApiFilePath: './openapi.yaml', // or ./openapi.json
        skipValidation: true, // optional, false by default
      },
    }, {
    operationIdFactory: (c: string, method: string) => method,
  });

  await app.listen(3000);
}
bootstrap();

NOTICE! File generation and client generation should be disabled in production as they are costly to startup time.

This project leverages the OpenAPITools/openapi-generator project via the npm package, @openapitools/openapi-generator-cli which is required to be installed globally. Accordingly, any client generators and configuration supported by this project are usable via Nest OpenAPI Tools.

To help with getting started, Nest OpenAPI Tools provides some classes with helpful defaults.

AxiosClientGeneratorOptions

• type = 'typescript-axios';
• outputFolderPath = '../typescript-api-client/src';
• additionalProperties = 'apiPackage=clients,modelPackage=models,withoutPrefixEnums=true,withSeparateModelsAndApi=true';
• openApiFilePath = './openapi.yaml';

Author - Kerry Ritter, BeerMoneyDev

Website - https://www.kerryritter.com/, https://www.beermoney.dev/