NestJS example

Would it be possible to add sample code for NestJS into https://github.com/vendia/serverless-express/tree/mainline/examples? For example, how to do something like this with v4.0.0?

import { Server } from 'http'
import { NestFactory } from '@nestjs/core'
import { AppModule } from './app.module'
import { Context, APIGatewayEvent } from 'aws-lambda'
import * as ServerlessExpress from '@vendia/serverless-express'
import express from 'express'
import { ExpressAdapter } from '@nestjs/platform-express'

let lambdaProxy : Server

async function bootstrap() {
  const expressServer = express()
  const app = await NestFactory.create(AppModule, new ExpressAdapter(expressServer))
  await app.init()
  return ServerlessExpress.createServer(expressServer)
}

export const handler = (event : APIGatewayEvent, context : Context) => {

  if (!lambdaProxy) {
    bootstrap().then((server) => {
      lambdaProxy = server
      ServerlessExpress.proxy(lambdaProxy, event, context)
    })
  } else {
    ServerlessExpress.proxy(lambdaProxy, event, context)
  }
}

[jlarmstrongiv]

Great idea! My file is similar:

lambda.ts

// transpiling https://github.com/claudiajs/claudia/issues/132
// no relative paths https://github.com/claudiajs/claudia/issues/40#issuecomment-218372727
// timeout https://stackoverflow.com/a/54086731
// aws gateway timeout https://github.com/vendia/serverless-express#considerations
// module.exports https://github.com/janaz/lambda-request-handler/pull/6

import type { Handler, Context } from 'aws-lambda';
import { Server } from 'http';
import { createServer, proxy } from 'aws-serverless-express';
import { eventContext } from 'aws-serverless-express/middleware';

import { NestFactory } from '@nestjs/core';
import {
  ExpressAdapter,
  NestExpressApplication,
} from '@nestjs/platform-express';
import { AppModule } from './app/app.module';
import { useGlobal } from './bootstrap';

// https://github.com/Microsoft/TypeScript/issues/13340
import express = require('express');

// NOTE: If you get ERR_CONTENT_DECODING_FAILED in your browser, this
// is likely due to a compressed response (e.g. gzip) which has not
// been handled correctly by aws-serverless-express and/or API
// Gateway. Add the necessary MIME types to binaryMimeTypes below

// https://github.com/awslabs/aws-serverless-express/blob/master/examples/basic-starter/lambda.js
const binaryMimeTypes: string[] = [
  'application/javascript',
  'application/json',
  'application/octet-stream',
  'application/xml',
  'font/eot',
  'font/opentype',
  'font/otf',
  'image/gif',
  'image/heic',
  'image/jpeg',
  'image/png',
  'image/svg+xml',
  'image/webp',
  'text/comma-separated-values',
  'text/css',
  'text/html',
  'text/javascript',
  'text/plain',
  'text/text',
  'text/xml',
];

let cachedServer: Server;

// Create the Nest.js server and convert it into an Express.js server
async function bootstrapServer(): Promise<Server> {
  if (!cachedServer) {
    const expressApp = express();
    const nestApp = await NestFactory.create<NestExpressApplication>(
      AppModule,
      new ExpressAdapter(expressApp),
    );
    nestApp.use(eventContext());

    // custom add global pipes, filters, interceptors, etc.
    useGlobal(nestApp);

    await nestApp.init();
    cachedServer = createServer(expressApp, undefined, binaryMimeTypes);
  }
  return cachedServer;
}

// Export the handler : the entry point of the Lambda function
export const handler: Handler = async (event: any, context: Context) => {
  // https://medium.com/safara-engineering/wiring-up-typeorm-with-serverless-5cc29a18824f
  context.callbackWaitsForEmptyEventLoop = false;
  cachedServer = await bootstrapServer();
  return proxy(cachedServer, event, context, 'PROMISE').promise;
};

bootstrap.ts

import { NestFactory } from '@nestjs/core';
import { AppModule } from './app/app.module';
import { NestExpressApplication } from '@nestjs/platform-express';
import helmet from 'helmet';

export async function bootstrap(): Promise<NestExpressApplication> {
  const app = await NestFactory.create<NestExpressApplication>(AppModule);
  return app;
}

export async function useGlobal(
  app: NestExpressApplication,
): Promise<NestExpressApplication> {
  app.use(helmet());
  app.disable('x-powered-by');
  return app;
}

EDIT: I added a helper to an npm package I’m working on. Rough around the edges, but at least I have it written down somewhere 😄

[michaelmerrill]

Alright, I think I ended up figuring it out. I’ve updated my repo. If I’m off or missing something let me know!