metamask-extension/development/build/styles.js

const pify = require('pify')
const gulp = require('gulp')
const sass = require('gulp-sass')
sass.compiler = require('node-sass')
const autoprefixer = require('gulp-autoprefixer')
const gulpStylelint = require('gulp-stylelint')
const watch = require('gulp-watch')
const sourcemaps = require('gulp-sourcemaps')
const rtlcss = require('gulp-rtlcss')
const rename = require('gulp-rename')
const pump = pify(require('pump'))
const { createTask } = require('./task')

// scss compilation and autoprefixing tasks
module.exports = createStyleTasks

function createStyleTasks ({ livereload }) {

  const prod = createTask('styles:prod', createScssBuildTask({
    src: 'ui/app/css/index.scss',
    dest: 'ui/app/css/output',
    devMode: false,
  }))

  const dev = createTask('styles:dev', createScssBuildTask({
    src: 'ui/app/css/index.scss',
    dest: 'ui/app/css/output',
    devMode: true,
    pattern: 'ui/app/**/*.scss',
  }))

  const lint = createTask('lint-scss', function () {
    return gulp
      .src('ui/app/css/itcss/**/*.scss')
      .pipe(gulpStylelint({
        reporters: [
          { formatter: 'string', console: true },
        ],
        fix: true,
      }))
  })

  return { prod, dev, lint }

  function createScssBuildTask ({ src, dest, devMode, pattern }) {
    return async function () {
      if (devMode) {
        watch(pattern, async (event) => {
          await buildScss()
          livereload.changed(event.path)
        })
      }
      await buildScss(devMode)
    }

    async function buildScss () {
      await pump(...[
        // pre-process
        gulp.src(src),
        devMode && sourcemaps.init(),
        sass().on('error', sass.logError),
        devMode && sourcemaps.write(),
        autoprefixer(),
        // standard
        gulp.dest(dest),
        // right-to-left
        rtlcss(),
        rename({ suffix: '-rtl' }),
        devMode && sourcemaps.write(),
        gulp.dest(dest),
      ].filter(Boolean))
    }
  }

}