Example repro for a SystemJS build issue when using Babel

test_systemjs_build_caching.js

/**
 * Assumes jspm's config.js contains configs to use Babel as the transpiler.
 */

var DevBuilder = require('jspm-dev-builder');
var path = require('path');
var ipc = require('ipc-light');
var fs = require('fs');

var appBuilder = new DevBuilder({
    expression: path.join(__dirname, '..', 'src', 'main'),
    outLoc: path.join(__dirname, '..', 'www', 'dev.js'),
    logPrefix: 'my-app',
    buildOptions: {
        minify: false,
        mangle: false,
        sourceMaps: true
    }
});

appBuilder.build().then(function () {

    console.log('App has been fully built, and is functional.');

    fs.appendFileSync('src/controllers/HomeController.js', '\n');
    appBuilder.build('src/controllers/HomeController.js').then(function(){

        console.log('App has been partially rebuilt, and is still functional.');

        fs.appendFileSync('src/controllers/HomeController.js', '\n');
        appBuilder.build('src/controllers/HomeController.js').then(function(){

            console.log('App is broken now, run www/dev.html to see error message.');
            process.exit(0);

        });
    });
});