SASSAsset.js

const Asset = require('../Asset');
const localRequire = require('../utils/localRequire');
const promisify = require('../utils/promisify');
const path = require('path');
const os = require('os');
const Resolver = require('../Resolver');

class SASSAsset extends Asset {
  constructor(name, options) {
    super(name, options);
    this.type = 'css';
  }

  async parse(code) {
    // node-sass should be installed locally in the module that's being required
    let sass = await localRequire('node-sass', this.name);
    let render = promisify(sass.render.bind(sass));
    const resolver = new Resolver({
      extensions: ['.scss', '.sass'],
      rootDir: this.options.rootDir
    });

    let opts =
      (await this.getConfig(['.sassrc', '.sassrc.js'], {packageKey: 'sass'})) ||
      {};
    opts.includePaths = (opts.includePaths || []).concat(
      path.dirname(this.name)
    );
    opts.data = opts.data ? opts.data + os.EOL + code : code;
    let type = this.options.rendition ? this.options.rendition.type : path.extname(this.name).toLowerCase().replace('.','');
    opts.indentedSyntax = typeof opts.indentedSyntax === 'boolean' ? opts.indentedSyntax : type === 'sass';

    opts.functions = Object.assign({}, opts.functions, {
      url: node => {
        let filename = this.addURLDependency(node.getValue());
        return new sass.types.String(`url(${JSON.stringify(filename)})`);
      }
    });
    
    opts.importer = opts.importer || [];
    opts.importer = Array.isArray(opts.importer) ? opts.importer : [opts.importer];
    opts.importer.push((url, prev, done) => {
      if (!/^(~|\.\/|\/)/.test(url)) {
        url = './' + url;
      } else if (!/^(~\/|\.\/|\/)/.test(url)) {
        url = url.substring(1);
      }
      resolver
        .resolve(url, prev === 'stdin' ? this.name : prev)
        .then(resolved => resolved.path)
        .catch(() => url)
        .then(file => done({file}))
        .catch(err => done(normalizeError(err)));
    });

    return await render(opts);
  }

  collectDependencies() {
    for (let dep of this.ast.stats.includedFiles) {
      this.addDependency(dep, {includedInParent: true});
    }
  }

  generate() {
    return [
      {
        type: 'css',
        value: this.ast ? this.ast.css.toString() : '',
        hasDependencies: false
      }
    ];
  }
}

module.exports = SASSAsset;

// Ensures an error inherits from Error
function normalizeError(err) {
  let message = 'Unknown error';

  if (err) {
    if (err instanceof Error) {
      return err;
    }

    message = err.stack || err.message || err;
  }

  return new Error(message);
}