This project contains an amplify project with one lambda function and one lambda layer. The Lambda function and the Lambda Layer implements some hello world code in typescript. When you deploy the app, npm scripts are triggered (as part of the amplify lifecycle hooks) and transpile the typescript to javascript.

Lambda Layer elements are accessible in the lambda function via /opt/. Because this folder doesn't exist on your local machine, you need path mapping in the tsconfig.

Install Amplify CLI globally

npm install -g @aws-amplify/cli

Clone the Project, Install Dependencies and Deploy the Project

• git clone https://github.com/StefanV85/LambdaLayerWithTS.git
• cd LambdaLayerWithTS
• amplify init => assign an AWS profile for your account
• npm install
• cd ./amplify/backend/function
• npm install
• cd ../../..
• amplify push

npm install -g @aws-amplify/cli

amplify init

• Choose the project name
• Choose your AWS profile to link your AWS account

amplify add function

• Select: Lambda function (serverless function)
• Answer the following Questions (e.g. Lambda Function Name)
• Select NodeJS as runtime
• Select "Hello World" as function template
• Select "No" for advanced Settings
• Select "No" for edit local Lambda function now
• Try out "amplify push" to push the Lambda Function to your AWS account
• After successfully push, you can test the Lambda function in the AWS Management Console

amplify add function

• Choose layer name
• Choose runtime (e.g. NodeJS)
• Choose which AWS Accounts should have access to this layer (e.g. recommend "Specific AWS Accounts"):
• Enter your AWS Account ID

amplify update function

• Choose Lambda function (serverless function)
• Select the existing Lambda Function
• Select "Lambda layers configuration"
• Select "yes" to enable Layers for this function
• select the existing Lambda layer
• select "no" for edit the local Lambda function now
• Try out "amplify push" to push the Lambda Function to your AWS account
• After successfully push, you can see in the AWS Management Console, that the Lambda function references to the Lambda layer

• Typescript should be handled in ./amplify/backend/function (one level over the function itself)
• The fact, that typescript is one layer over the specific lambdafunction folders, it's not necassary to install typescript as devDependency on each Lambda Function. Additionally: Amplify uploads all dependencies to the cloud. Therefore you should be carefully with devDependencies inside the lambdafunction folders, because it's increase the deployment time.

- cd ./amplify/backend/function
- npm init
- npm install typescript --save-dev
- npm install @types/node --save-dev

• Rename ./amplify/backend/function/LambdaName/src/index.js to "index.ts"
• Enhance code with typescript hello world

{
    exports.handler = async (event) => {
    let message: string = 'Hello, World!'
    console.log(message)

    const response = {
        statusCode: 200,
        body: JSON.stringify(message),
    }
    return response
    }
}

• create ./amplify/backend/function/LambdaName/src/tsconfig.json

{
    "compilerOptions": {
        "module": "commonjs",
        "target": "es6",
        "outDir": ".",
        "rootDir": ".",
        "sourceMap": true,
        "strict": false,
        "experimentalDecorators": true,
        "baseUrl": ".",
        "resolveJsonModule": true,
        "paths": {
        }
    },
    "exclude": []
}

• Add package.json on root level of the project (if doesn't exist yet)
• npm init
• Add a Script for your Lambda Function: "amplify:< LambdaFunctionName>"
• Add a Script for your Lambda Layer: "amplify:< LambdaLayerName>"
• Because of the prefix amplify:, the script will be triggered automatically be the amplify cli

{
  "name": "lambdalayerwithts",
  "version": "1.0.0",
  "description": "- amplify init\r -- Choose the project name\r -- Choose your aws profile to link your aws account",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1",
    "amplify:LambdaFunc1": "cd amplify/backend/function && npm run tscLambdaFunc1",
    "amplify:lambdalayerwithtsLambdaLayer1": "cd amplify/backend/function && npm run tsclambdalayerwithtsLambdaLayer1"
  },
  "repository": {
    "type": "git",
    "url": "git+https://github.com/StefanV85/LambdaLayerWithTS.git"
  },
  "author": "",
  "license": "ISC",
  "bugs": {
    "url": "https://github.com/StefanV85/LambdaLayerWithTS/issues"
  },
  "homepage": "https://github.com/StefanV85/LambdaLayerWithTS#readme"
}

• Add a corresponding script for your Lambda Function in ./amplify/backend/function/package.json

{
  "name": "function",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1",
    "tscLambdaFunc1": "tsc -p ./LambdaFunc1/src/",
    "tsclambdalayerwithtsLambdaLayer1": "tsc -p ./lambdalayerwithtsLambdaLayer1/opt/"
  },
  "author": "",
  "license": "ISC",
  "dependencies": {},
  "devDependencies": {
    "@types/node": "^16.4.0",
    "typescript": "^4.3.5"
  }
}

Create an Build Task, to be able to trigger the transpile via Ctrl+Shift+B manually too

• create ./.vscode/tasks.json

{
  "version": "2.0.0",
  "tasks": [
    {
      "label": "LambdaFunc1 TypeScript->JavaScript",
      "type": "npm",
      "group": "build",
      "script": "amplify:LambdaFunc1",
      "problemMatcher": []
    },
    {
      "label": "LambdaLayer TypeScript->JavaScript",
      "type": "npm",
      "group": "build",
      "script": "amplify:lambdalayerwithtsLambdaLayer1",
      "problemMatcher": []
    }
  ]
}

• Try out "amplify push" to transpile and push the Lambda code to the cloud
• After pushing successfully you should see the transpiled javascript code in the AWS Management Console

• Create ./amplify/backend/function/layerName/opt/Shared/Logger/Logger.ts

export class Logger {
  log(message: string) {
    console.log(message)
  }
}

• create ./amplify/backend/function/layerName/opt/tsconfig.json

{
    "compilerOptions": {
        "module": "commonjs",
        "target": "es6",
        "outDir": ".",
        "rootDir": ".",
        "sourceMap": true,
        "strict": false,
        "experimentalDecorators": true,
        "resolveJsonModule": true,
        "baseUrl": ".",
        "skipLibCheck": true
    },
    "include": ["**/*"],
    "exclude": ["node_modules"]
}

In the Cloud, the layer code is accessable in the path /opt/ Because /opt/ doesn't exist locally, we introduce path mapping in tsconfig

{
  "compilerOptions": {
    "module": "commonjs",
    "target": "es6",
    "outDir": ".",
    "rootDir": ".",
    "sourceMap": true,
    "strict": false,
    "experimentalDecorators": true,
    "baseUrl": ".",
    "resolveJsonModule": true,
    "paths": {
      "/opt/Shared/Logger/Logger": [
        "../../lambdalayerwithtsLambdaLayer1/opt/Shared/Logger/Logger"
      ]
    }
  },
  "exclude": []
}

Remark Pathmapping in tsconfig is sometime not considerred immediatly by the IDE. Maybe you have to restart your IDE.

// @ts-ignore
import { Logger } from '/opt/Shared/Logger/Logger'

exports.handler = async (event) => {
  let message: string = 'Hello, World!'
  Logger.log(message)

  const response = {
    statusCode: 200,
    body: JSON.stringify(message),
  }
  return response
}

• Try out "amplify push" to transpile and push the changes to the cloud
• Test your Lambda Code in the AWS Management Console.