bootstrap

#!/opt/bin/node

const fs = require('fs')
const CoffeeScript = require('coffeescript')

// We'll set this so all later .coffee files we require() are
// compiled/transpiled automatically.
CoffeeScript.register()

// bootstrap.coffee is our port of the node-custom-lambda (https://github.com/
// lambci/node-custom-lambda) bootstrap.js. This file handles the lifecycle of
// the lambda. Note: when a lambda runs this file, the cwd() is /var/task
const bootstrap = '/opt/bootstrap.coffee'

// These are options we pass to the CoffeeScript compiler.
const options = {
    bare: true,
    header: false,
    sourceMap: false,
    inlineMap: false,
    // Due to our execution happening inside /var/task but our babel.config.js
    // located in /opt, the transpilation step could never find our babel config
    // and would fail. We needed to pass the "root" option to babel to fix this
    // but the coffeescript cli --transpile option was unfortunately just a 
    // boolean flag.
    // The workaround was to run our bootstrap.coffee using the coffescript
    // nodeJS api instead (hence this file is a nodeJS script) where it is
    // possible to pass the required 'root' option.
    transpile: { root: '/opt/' }
}

fs.readFile(bootstrap, 'utf8', (err, data) => {
    if (err) {
        throw new Error(`Could not find ${bootstrap}: ${err.code} ${err.message}`);
    }
    // Unlike your everyday coffeescript workflow, we're not writing the
    // compiled output to disk but rather evaluated on the fly. The result is
    // that we can save a few millisecs by skipping the i/o.
    CoffeeScript.run(data, options);
});