converter.js

exports.convert = convert;

var fs = require('fs');
var path = require('path');
var sass = require('node-sass');
var glob = require('glob');

function convert(logger, projectDir, options) {
  return new Promise(function (resolve, reject) {
    options = options || {};

    var sassFilesPath = path.join(projectDir, 'app/**/*.scss');
    var sassImportPaths = [
      path.join(projectDir, 'app/'),
      path.join(projectDir, 'node_modules/')
    ];
    //console.log("SASS Import Path", sassImportPaths);

    var sassFiles = glob.sync(sassFilesPath, {follow: true}).filter(function (filePath) {
      if (!(sassImportPaths.find(function (element) {return path.dirname(filePath) === element}))) {
        sassImportPaths.push(path.dirname(filePath));
      }
      var parts = filePath.split('/');
      var filename = parts[parts.length - 1];
      return filePath.indexOf("App_Resources") === -1 && filename.indexOf("_") !== 0;
    });

    if (sassFiles.length === 0) {
      //No sass files in project; skip parsing
      resolve();
    } else {
      var i = 0;
      var loopSassFilesAsync = function (sassFiles) {
        parseSass(sassFiles[i], sassImportPaths, function (e) {
          if (e !== undefined) {
            //Error in the LESS parser; Reject promise
            reject(Error(sassFiles[i] + ' SASS CSS pre-processing failed. Error: ' + e));
          }

          i++; //Increment loop counter

          if (i < sassFiles.length) {
            loopSassFilesAsync(sassFiles);
          } else {
            //All files have been processed; Resolve promise
            resolve();
          }
        });
      }

      loopSassFilesAsync(sassFiles);
    }
  });
}

function parseSass(filePath, importPaths, callback) {
  var sassFileContent = fs.readFileSync(filePath, {encoding: 'utf8'});
  var cssFilePath = filePath.replace('.scss', '.css');

  if (sassFileContent.trim().length === 0) {
    // No SASS content write an empty file
    fs.writeFile(cssFilePath, '', 'utf8', function () {
      callback();
    });
    return;
  }

  sass.render({
    data: sassFileContent,
    includePaths: importPaths,
    outFile: cssFilePath,
    outputStyle: 'compressed'
  }, function (e, output) {
    if (e) {
      //Callback with error
      callback(e);
    }

    if (output && output.css) {
      output = output.css;
    } else {
      output = '';
    }

    fs.writeFile(cssFilePath, output, 'utf8', function () {
      //File done writing
      callback();
    });
  });
}