gulpfile I use for polymer

gulpfile.js

/**
Structure used:
Source files are in /app
There are php files in /app/private_php and /app/public_php
Static files (elements, bower_components) are in /app/static

Builds into /dist-dev and /dist-prod
*/

var gulp = require('gulp');
var $ = require('gulp-load-plugins')();
var path = require('path');
var bowerFiles = require('main-bower-files');
var merge = require('merge-stream');
var del = require('del');
var runSequence = require('run-sequence');
var pump = require('pump');

var paths = {
    scripts: 'app/static/**/*.js',
    styles: ['./app/**/*.css', './app/**/*.scss'],
    index: './app/private_php/index.php',
    html: './app/static/**/*.html',
    distDev: './dist-dev',
    distProd: './dist-prod'
};

var AUTOPREFIXER_BROWSERS = [
  'ie >= 10',
  'ie_mob >= 10',
  'ff >= 30',
  'chrome >= 34',
  'safari >= 7',
  'opera >= 23',
  'ios >= 7',
  'android >= 4.0',
  'bb >= 10'
];

var distDev = function(subpath) {
    return !subpath ? paths.distDev : path.join(paths.distDev, subpath);
};

var distProd = function(subpath) {
    return !subpath ? paths.distProd : path.join(paths.distProd, subpath);
};

var styleTask = function(stylesPath, srcs) {
    var src = gulp.src(srcs.map(function(src) {
      return path.join('app', stylesPath, src);
    }));

    var sass = src.pipe($.changed(stylesPath, {extension: '.scss'}))
    .pipe($.sass());

    var css = src.pipe($.changed(stylesPath, {extension: '.css'}));

    return merge(sass, css)
    .pipe($.autoprefixer(AUTOPREFIXER_BROWSERS))
    .pipe(gulp.dest(distDev(stylesPath)))
    .pipe($.size({title: stylesPath}))
    .pipe(gulp.dest('.tmp/' + stylesPath))
    .pipe($.cleanCss())
    .pipe(gulp.dest(distProd(stylesPath)))
    .pipe($.size({title: stylesPath + " css min"}));
};

var imageOptimizeTask = function(src) {
  return gulp.src(src)
    .pipe($.imagemin({
      progressive: true,
      interlaced: true
    }))
    .pipe(gulp.dest(distDev('static/images')))
    .pipe(gulp.dest(distProd('static/images')))
    .pipe($.size({title: 'images'}));
};

// Compile and automatically prefix stylesheets
gulp.task('styles', function() {
  return styleTask('/static/styles', ['**/*css']);
});

gulp.task('images', function() {
  return imageOptimizeTask('app/static/images/**/*');
});

gulp.task('copyDev', function() {
    return gulp.src([
        'app/**',
        '!app/static/styles/**/*css',
        '!**/.DS_Store'
    ], {
        dot: true
    })
    .pipe(gulp.dest(distDev()))
    .pipe($.size({
        title: 'copyDev'
    }));
});

gulp.task('copyProd', function() {
    var app = gulp.src([
      'app/**',
      '!app/static/styles/**/*css',
      '!app/test/**',
      '!app/static/elements/**',
      '!app/static/bower_components/**',
      '!**/.DS_Store'
    ], {
      dot: true
  }).pipe(gulp.dest(distProd()));

    // Copy over only the bower_components we need
    // These are things which cannot be vulcanized
    var bower = gulp.src([
      'app/static/bower_components/{webcomponentsjs,promise-polyfill,moment}/**/*'
  ]).pipe(gulp.dest(distProd('/static/bower_components')));

    return merge(app, bower)
      .pipe($.size({
        title: 'copyProd'
      }));
});

//Vulcanize for production
gulp.task('vulcanize', function() {
  return gulp.src('app/static/elements/*elements.html')
    .pipe($.vulcanize({
      stripComments: true,
      inlineCss: true,
      inlineScripts: true
    }))
    .pipe(gulp.dest(distProd('static/elements')))
    .pipe($.size({title: 'vulcanize'}));
});

//Minify html in production dir
gulp.task('minifyHtml', function() {
    return gulp.src([distProd('/**/*.html'),
            distProd('/**_php/*.php')])
        .pipe($.size({title: 'HTML'}))
        .pipe($.htmlmin({
            collapseWhitespace: true,
            minifyCSS: true,
            minifyJS: false,
            preserveLineBreaks: true,
            ignoreCustomFragments: [ /<%[\s\S]*?%>/g, /<\?[\s\S]*?(\?>|$)/g ],
            removeComments: true
        }))
        .pipe(gulp.dest(distProd()))
        .pipe($.size({title: 'HTML min'}))
});

gulp.task('minifyJs', function(cb) {
    runSequence('prodJsSize', '_minifyJs', 'prodJsSize', cb);
});

//Didn't work to put size() in the pump, had to split it up
gulp.task('_minifyJs', function(cb) {
    pump([
        gulp.src(distProd('/**/scripts/**/*.js')),
        $.uglify({ compress: false }),
        gulp.dest(distProd())
    ], cb);
});

gulp.task('prodJsSize', function() {
    return gulp.src(distProd('/**/scripts/**/*.js'))
        .pipe($.size({title: 'js'}));
});

// Clean output directory
gulp.task('clean', function() {
  return del(['.tmp', distDev(), distProd()]);
});

// Build production files, the default task
gulp.task('default', ['clean'], function(cb) {
  runSequence(
    ['copyDev', 'copyProd', 'styles'],
    'images',
    'vulcanize',
    'minifyHtml',
    'minifyJs',
    cb);
});