Using esbuild in your Serverless Framework Project

readme.md

Using esbuild in your Serverless Framework Project

How to use esbuild to transpile and bundle your TypeScript Lambda functions in a Serverless Framework project - all without using any plugins!

Example source code from article Using esbuild in your Serverless Framework Project.

build.js

const fs = require('fs')
const cloudformationSchema = require('@serverless/utils/cloudformation-schema')
const esbuild = require('esbuild')
const yaml = require('js-yaml')
const rimraf = require('rimraf')

const SERVERLESS_YML_PATH = './serverless.yml'
const OUT_DIR = './dist'

// ref: https://esbuild.github.io/api/#simple-options
const ESBUILD_CONFIG = {
  bundle: true,
  external: ['aws-sdk'],
  format: 'cjs',
  minify: true,
  platform: 'node',
  outbase: 'src',
  outdir: OUT_DIR,
}

async function getConfig() {
  return yaml.loadAll(fs.readFileSync(SERVERLESS_YML_PATH), {
    schema: cloudformationSchema,
  })[0]
}

;(async function main() {
  rimraf.sync(OUT_DIR)

  const { functions, provider } = await getConfig()

  const handlers = Object.entries(functions)
    .map(([, fn]) => fn.handler.replace('dist/', 'src/'))
    .map((fn) => {
      const parts = fn.split('.')
      const path = parts.slice(0, parts.length - 1).join('.')

      return fs.existsSync(path + '.ts') ? path + '.ts' : path + '.js'
    })

  console.info('Building handlers..')

  await esbuild
    .build({
      ...ESBUILD_CONFIG,
      entryPoints: handlers,
      target: provider.runtime
        ? 'node' + provider.runtime.match(/\d+/g)[0]
        : 'node14',
    })
    .catch(() => process.exit(1))

  handlers.map((handler) => {
    const bundlePath = handler.replace('.ts', '.js').replace('src/', 'dist/')
    const stat = fs.statSync(bundlePath)

    console.log(
      bundlePath,
      '-',
      +(stat.size / 1024 / 1024).toPrecision(3),
      'MB',
    )
  })
})()

package.json

{
  "name": "example",
  "scripts": {
    "build": "node build.js",
    "predeploy": "npm run build",
    "deploy": "serverless deploy"
  },
  "devDependencies": {
    "@types/aws-lambda": "8.10.83",
    "esbuild": "0.12.22",
    "js-yaml": "4.1.0",
    "serverless": "2.55.0",
    "rimraf": "3.0.2",
    "typescript": "4.3.5"
  }
}

serverless.yml

service: example

provider:
  name: aws
  runtime: nodejs14.x

package:
  excludeDevDependencies: false
  patterns:
    - '!./**'
    - './dist/**'

functions:
  example:
    description: An example lambda function
    handler: dist/example.handler
    memorySize: 256
    events:
      - http: GET /example

src-example.ts

// Save as: src/example.ts

import * as AWSLambda from 'aws-lambda'

export default async function exampleHandler(
  event: AWSLambda.APIGatewayProxyEvent,
  context: AWSLambda.Context,
): Promise<AWSLambda.APIGatewayProxyStructuredResultV2> {
  return {
    statusCode: 200,
    body: JSON.stringify({ event, context }),
  }
}