Hack to enable source maps in with gulp-sourcemaps and autoprefixer.

gulp-autoprefixer-map.js

#!/usr/bin/env node

/*
  Hack to enable source maps in with gulp-sourcemaps and autoprefixer.

  Created by null on 12/08/14.

  npm --save-dev install through2
  npm --save-dev install autoprefixer
  npm --save-dev install vinyl-sourcemaps-apply

    var sourcemaps = require('gulp-sourcemaps');
    var concat = require('gulp-concat'); // Supports gulp-sourcemaps
    var prefixer = require('./gulp-autoprefixer-map.js');
 
    gulp.task('css', [], function() {
      gulp.src('src/*.css')
       .pipe(sourcemaps.init())
       .pipe(concat('app.css'))
       .pipe(prefixer())
       .pipe(sourcemaps.write('.'))
       .pipe(gulp.dest('dest/'))
    });

 */

var through = require('through2');
var prefix = require('autoprefixer');
var applySourceMap = require('vinyl-sourcemaps-apply');

module.exports = function(browsers, options) {

  options = options || {};

  return through.obj(function(file, enc, cb) {

    if(file.isStream()) {
      throw new Error('Streams not supported');
    }

    if(!file.isNull()) {

      if(file.sourceMap) {
        options.map = {
          annotation: false
        };
        options.to = options.from = file.relative;
      }

      var contents = file.contents.toString();

      var result = prefix(browsers).process(contents, options);
      contents = result.css;

      file.contents = new Buffer(contents);

      if(file.sourceMap) {
        applySourceMap(file, result.map.toString());
      }
    }

    this.push(file);
    cb();

  });

};