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:

1{
2  "scripts": {
3    "amplify:generateReport": "cd amplify/backend/function/generateReport && tsc -p ./tsconfig.json && cd -"
4  },
5}

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

1{
2  "compilerOptions": {
3    "allowSyntheticDefaultImports": true,
4    "lib": ["dom", "esnext"],
5    "module": "commonjs",
6    "moduleResolution": "node",
7    "skipLibCheck": true,
8    "resolveJsonModule": true,
9    "outDir": "./src",
10    "baseUrl": "./",
11    "rootDir": "./lib",
12    "paths": {
13      "src": ["./lib"]
14    }
15  }
16}

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:

1import AWS from 'aws-sdk';

Change to this:

1import * 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:

1{
2  "scripts": {
3    "amplify:generateReport": "cd amplify/backend/function/generateReport && babel lib -d src && cd -"
4  },
5  "devDependencies": {
6    "@babel/cli": "^7.5.5",
7    "@babel/preset-env": "^7.5.5",
8  }
9}

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):

1{
2  "presets": [
3    [
4      "env",
5      {
6        "exclude": ["transform-regenerator"],
7        "targets": {
8          "node": "10.18"
9        }
10      }
11    ]
12  ],
13  "plugins": [
14    "transform-async-to-generator",
15    "transform-exponentiation-operator",
16    "transform-object-rest-spread"
17  ]
18}

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.