hook.bundle.js

var cssInject = "(function(c){var d=document,a='appendChild',i='styleSheet',s=d.createElement('style');s.type='text/css';d.getElementsByTagName('head')[0][a](s);s[i]?s[i].cssText=c:s[a](d.createTextNode(c));})";

var escape = function (source) {
    return source
    .replace(/(["\\])/g, '\\$1')
    .replace(/[\f]/g, '\\f')
    .replace(/[\b]/g, '\\b')
    .replace(/[\n]/g, '\\n')
    .replace(/[\t]/g, '\\t')
    .replace(/[\r]/g, '\\r')
    .replace(/[\ufeff]/g, '')
    .replace(/[\u2028]/g, '\\u2028')
    .replace(/[\u2029]/g, '\\u2029');
};

exports.translate = function (load) {
    load.metadata.format = 'defined';
};

exports.bundle = function (loads, compileOpts, outputOpts) {
    var stubDefines = loads.map(function (load) {
        return (compileOpts.systemGlobal || "System") + ".register('" + load.name + "', [], false, function() {});";
    }).join('\n');

    var lessc = System._nodeRequire("less");
    var compilePromise = function (load) {
        return lessc.render(load.source, {
            filename: load.name.replace(/^file:(\/+)?/i, '')
        })
        .then(function (output) {
            // output.css = string of css
            // output.map = string of sourcemap
            // output.imports = array of string filenames of the imports referenced

            return output.css;
        })
    };

    var cssOptimize = outputOpts.minify && outputOpts.cssOptimize !== false;
    var CleanCSS = System._nodeRequire("clean-css");
    var cleaner = new CleanCSS({
        advanced: cssOptimize,
        agressiveMerging: cssOptimize,
        mediaMerging: cssOptimize,
        restructuring: cssOptimize,
        shorthandCompacting: cssOptimize,

        ////sourceMap: !!outputOpts.sourceMaps,
        ////sourceMapInlineSources: outputOpts.sourceMapContents
    });

    return Promise.all(loads.map(compilePromise))
        .then(function (cssResults) {
            var all = cssResults.join("");
            var minified = cleaner.minify(all).styles;
            return [stubDefines, cssInject, "('" + escape(minified) + "');"].join('\n');
        });
};