gulpfile.js

var gulp = require('gulp');
var sass = require('gulp-sass');
var postcss = require('gulp-postcss');
var cssnano = require('gulp-cssnano');
var sourcemaps = require('gulp-sourcemaps');
var merge = require('merge-stream');
var clone = require('gulp-clone');

var bower_path = 'vendor/bower_components';

var paths = [
    'bootstrap'         : bower_path + '/bootstrap-sass/assets',
    ];

gulp.task('front-sass-ex', function()
{
    var processors = [
        require("postcss-cssnext")({
            'browers': ['last 2 version'],
            'customProperties': true,
            'colorFunction': true,
            'customSelectors': true,
            'sourcemap': true,
            'compress': false
        })
    ];
    var css = gulp.src(resource_path + '/sass/app.scss')
        .pipe(sourcemaps.init())
        .pipe(sass(
            {
                outputStyle: 'expanded',
                sourceMap: true,
                sourceMapRoot: [
                    resource_path + '/sass/app/',
                    paths.bootstrap + '/stylesheets'
                ],
                includePaths: [
                    require('node-bourbon').includePaths,
                    require('node-neat').includePaths,
                    paths.bootstrap + '/stylesheets'
                ],
                noCache: true,
                errLogToConsole: true
            }))
        .pipe(postcss(processors))
        .pipe(gulp.dest('public/assets/css'));

    var min = css.pipe(clone())
        .pipe(cssnano({discardComments: {removeAll: true}}))
        .pipe(rename('app.min.css'));

    return merge(css, min)
        .pipe(sourcemaps.write('.', {
            sourceRoot: resource_path + '/sass/app/',
            includeContent: false
        }))
        .pipe(gulp.dest(''));
});