Duo gulp integration

gulpnduo.js

/**
 * Module Dependencies
 */

var debug = require('debug')('lapwing:build');
var relative = require('path').relative;
var resolve = require('path').resolve;
var extname = require('path').extname;
var uglify = require('gulp-uglify');
var Batch = require('better-batch');
var root = require('../root-path');
var yieldly = require('yieldly');
var Glob = require('glob').sync;
var map = require('map-stream');
var join = require('path').join;
var csso = require('gulp-csso');
var gulp = require('gulp');
var Duo = require('duo');

/**
 * Expose `build`
 */

module.exports = yieldly(build);

/**
 * Gulp plugins
 */

var myth = require('gulp-myth');

/**
 * Environment
 */

var dev = 'development' == process.env.NODE_ENV;

/**
 * File extension maps
 */

var extmap = {
  'styl': 'css'
};

/**
 * Build
 *
 * @param {String} glob
 * @param {Function} fn
 * @api public
 */

function build(glob, fn) {
  var files = Glob(glob);
  var segments = segment(files);

  Batch()
    .push(wrap(styles, segments.css))
    .push(wrap(scripts, segments.js))
    .end(fn);

  // wrap batch
  function wrap(fn, files) {
    return function (done) {
      fn(files, done);
    }
  }
}

/**
 * Compile styles
 *
 * @param {Function} fn
 * @return {Gulp} stream
 * @api private
 */

function styles(styles, fn) {
  var s = gulp.src(styles)
    .pipe(logger('building'))
    .pipe(duo())
    .on('error', fn)
    .pipe(myth())
    .on('error', fn)

  if (!dev) {
    s.pipe(csso())
     .on('error', fn);
  }

  s.pipe(gulp.dest('build'))
   .on('error', fn)
   .on('end', fn);

  return s;
}

/**
 * Compile javascript
 *
 * @param {Array} scripts
 * @return {Function} fn
 */

function scripts(scripts, fn) {
  var s = gulp.src(scripts)
    .pipe(logger('building'))
    .pipe(duo())
    .on('error', fn);

  if (!dev) {
    s.pipe(uglify())
     .on('error', fn);
  }

  s.pipe(gulp.dest('build'))
   .on('error', fn)
   .on('end', fn);

  return s;
}

/**
 * Build with Duo
 *
 * @return {Function}
 */

function duo() {
  return map(function(file, fn) {
    // change the base to root
    file.base = root;

    Duo(root)
      .entry(file.path)
      .run(function(err, src) {
        if (err) return fn(err);
        file.contents = new Buffer(src);
        fn(null, file);
      });
  });
}

/**
 * Segment files by extension
 *
 * @param {Array} files
 * @return {Object}
 * @api private
 */

function segment(files) {
  var out = {};

  files.map(function(file) {
    var ext = extname(file).slice(1);
    ext = extmap[ext] ? extmap[ext] : ext;
    if(!out[ext]) out[ext] = [];
    out[ext].push(file);
  });

  return out;
}

/**
 * Logging
 *
 * @param {Stream} stream
 * @api private
 */

function logger(event) {
  return map(function(file, fn) {
    debug('%s: %s', relative(root, file.path), event);
    fn(null, file);
  });
}

koa-middleware.js

/**
 * Module Dependencies
 */

var build = require('../build')

/**
 * Expose `middleware`
 */

module.exports = middleware;

/**
 * Initialize `middleware`
 *
 * @param {String} glob
 * @return {Generator}
 */

function middleware(glob) {
  return function *(next) {
    yield build(glob);
    yield next;
  }
}

Usage:

build(join(__dirname, 'home.{js,styl,css}'), function(err) {
  // built
});

This allows you to easily integrate with middleware & only build the files you need for that page.

Here's a simpler, less-robust version just to demonstrate the idea: https://gist.github.com/johntron/1c057bbad6d477362ab6