loopback 4 generate openapi.json on build

Question

I would like to generate an openapi.json file on a loopback 4 api without having to start the server and request the openapi endpoint. I could not find any way to do it in the loopback documentation.

Is there any way to generate that file ?

Answer 1

Method getApiSpec() from rest.server.ts @loopback/rest/rest.server.ts.

add method in index.ts:

// Node module: @loopback/example-express-composition
// This file is licensed under the MIT License.
// License text available at https://opensource.org/licenses/MIT

import { ExpressServer } from './server';
import { ApplicationConfig } from '@loopback/core';
import { RequestContext } from '@loopback/rest';

export { ExpressServer };

export async function main(options: ApplicationConfig = {}) {
  const server = new ExpressServer(options);
  await server.boot();
  await server.start();

  console.log('Server is running at http://127.0.0.1:3000');
}

export async function getOpenApiJSONtoFile(options: ApplicationConfig = {}) {
  const server = new ExpressServer(options);

  await server.boot();

  return server.lbApp.restServer.getApiSpec()
}

and create file for create json:

const application = require('./dist');
const fs = require('fs');


const config = {
  rest: {
    port: +process.env.PORT || 3000,
    host: process.env.HOST || 'localhost',
    openApiSpec: {
      // useful when used with OpenAPI-to-GraphQL to locate your application
      setServersFromRequest: true,
    },
    // Use the LB4 application as a route. It should not be listening.
    listenOnStart: false,
  },
};
application.getOpenApiJSONtoFile(config)
  .then(result => {
    let data = JSON.stringify(result);
    fs.writeFileSync('openapi.json', data);
  })
  .catch(err => { console.log(err) });