Generate swagger 2.0 yaml using swagger 4.x package - swagger

Question

I am going to integrate my API server to Google Cloud Endpoints.
And Google Cloud Endpoints supports swagger 2.0 as of now.
But my dependencies/libraries are up versions now. So I want to generate swagger 2.0 yaml file without downgrading swagger library version (api end points are already described with swagger 4.x - openapi 3.0 spec).
Nestjs and swagger dependencies (package.json):
...
"#nestjs/common": "^7.0.0",
"#nestjs/config": "^0.4.0",
"#nestjs/core": "^7.0.0",
"#nestjs/platform-express": "^7.0.0",
"js-yaml": "^3.14.0",
...
"#nestjs/swagger": "^4.5.4",
"swagger-ui-express": "^4.1.4",
...
And swagger generator script:
import { NestFactory } from '#nestjs/core';
import { AppModule } from './app.module';
import * as fs from 'fs'
import * as yaml from 'js-yaml'
const generateSwaggerYaml = async () => {
const app = await NestFactory.create(AppModule);
const options = new DocumentBuilder()
.setTitle('API Title')
.setDescription('API Description')
.build()
const document = SwaggerModule.createDocument(app, options)
fs.writeFileSync("./openapi-run.yaml", yaml.safeDump(document))
}
generateSwaggerYaml()
And output of script is openapi 3.0 spec :(
openapi: 3.0.0
info:
title: API Title
description: API Description.
version: 1.0.0
contact: {}
tags: []
servers: []
...
Is there any option/way to generate swagger2.0 yaml from openapi 3.0 document?
How can I downgrade openapi 3.0 spec to swagger 2.0 spec?

Answer 1

I use this project from github for that very purpose: https://github.com/LucyBot-Inc/api-spec-converter
For openapi 3 yaml to swagger 2 yaml, it's as simple as $ api-spec-converter --from openapi_3 --syntax yaml --to swagger_2 ${f} > ${SWAGGER_V2_FILE}