Build options

In some cases, it might be necessary to execute a script before a function is deployed, e.g. to transpile Typescript or ES6 with Babel or with tsc into a format that is supported by the AWS Lambda's node runtime. amplify push will look for a script definition in the project root's package.json with the name amplify:<resource_name> and run it right after npm install is called in the function resource's src directory.

Example: Transpiling Typescript code with TSC

Make sure you have the tsc command installed globally by running npm install -g typescript or locally by running npm install --save-dev typescript

Let's say, a function resource has been created with amplify function add and it is called generateReport. The ES6 source code for this function is located in amplify/backend/function/generateReport/lib and the resource's src directory only contains the auto-generated package.json for this function. In order to compile TypeScript, you have to add the following script definition to your project root's package.json:

{
  "scripts": {
    "amplify:generateReport": "cd amplify/backend/function/generateReport && tsc -p ./tsconfig.json && cd -"
  },
}

Navigate into amplify/backend/function/generateReport and create tsconfig.json then add the following to it:

{
  "compilerOptions": {
    "allowSyntheticDefaultImports": true,
    "lib": ["dom", "esnext"],
    "module": "commonjs",
    "moduleResolution": "node",
    "skipLibCheck": true,
    "resolveJsonModule": true,
    "outDir": "./src",
    "baseUrl": "./",
    "rootDir": "./lib",
    "paths": {
      "src": ["./lib"]
    }
  }
}

Note: It is important to note that if you are using aws-sdk in your TypeScript file, you will get a timeout if you attempt to import it with the following:

import AWS from 'aws-sdk';

Change to this:

import * as AWS from 'aws-sdk';

Once you run amplify push, the amplify:generateReport script will be executed, either by yarn or by npm depending on the existence of a yarn.lock file in the project root directory.

Example: Transpiling ES6 code with Babel

Let's say, a function resource has been created with amplify function add and it is called generateReport. The ES6 source code for this function is located in amplify/backend/function/generateReport/lib and the resource's src directory only contains the auto-generated package.json for this function. In order to run Babel, you have to add the following script definition and dev dependencies to your project root's package.json:

{
  "scripts": {
    "amplify:generateReport": "cd amplify/backend/function/generateReport && babel lib -d src && cd -"
  },
  "devDependencies": {
    "@babel/cli": "^7.5.5",
    "@babel/preset-env": "^7.5.5",
  }
}

Babel needs to be configured properly so that the transpiled code can be run on AWS Lambda. This can be done by adding a .babelrc file to the resource folder (amplify/backend/function/generateReport/.babelrc in this case):

{
  "presets": [
    [
      "env",
      {
        "exclude": ["transform-regenerator"],
        "targets": {
          "node": "10.18"
        }
      }
    ]
  ],
  "plugins": [
    "transform-async-to-generator",
    "transform-exponentiation-operator",
    "transform-object-rest-spread"
  ]
}

Once you run amplify push, the amplify:generateReport script will be executed, either by yarn or by npm depending on the existence of a yarn.lock file in the project root directory.