index.js

var fs = require('fs');
var path = require('path');
var mkdirp = require('mkdirp');
var includePathSearcher = require('include-path-searcher');
var quickTemp = require('quick-temp');
var mapSeries = require('promise-map-series');
var less = require('less');
var _ = require('lodash');
var RSVP = require('rsvp');

var Writer = require('broccoli-writer');
var helpers = require('broccoli-kitchen-sink-helpers');

module.exports = LessCompiler;
LessCompiler.prototype = Object.create(Writer.prototype);
LessCompiler.prototype.constructor = LessCompiler;

function LessCompiler (sourceTrees, inputFile, outputFile, options) {
  if (!(this instanceof LessCompiler)) return new LessCompiler(sourceTrees, inputFile, outputFile, options);
  this.sourceTrees = sourceTrees;
  this.inputFile = inputFile;
  this.outputFile = outputFile;
  this.lessOptions = options || {};

  this.cache = {};

  this.cached = undefined;
}

LessCompiler.prototype.write = function (readTree, destDir) {
  var self = this;

  var destFile = destDir + '/' + this.outputFile;
  mkdirp.sync(path.dirname(destFile));
  return mapSeries(this.sourceTrees, readTree)
    .then(function (includePaths) {

      var newCache = {};

      // glob off of input tree
      var inputFiles = includePaths.map(function(path) {
        var files = helpers.multiGlob(['**/*.less'], {cwd: path});
        return files.map(function(filepath) { return path + '/' + filepath; });
      });

      var needRecompile = false;

      _.flatten(inputFiles).forEach(function(path) {
        var statsHash = helpers.hashStats(fs.statSync(path));
        if (self.cache[statsHash] === undefined) {
          // cache miss, recompile needed!
          needRecompile = true;
        }
        newCache[statsHash] = true;  // eventually this could store some extra state
      });

      self.cache = newCache;

      if (needRecompile === false) {
        fs.writeFileSync(destFile, self.cached, { encoding: 'utf8' });
        return RSVP.Promise.resolve(self.tmpDestDir);
      }

      var lessOptions = {
        filename: includePathSearcher.findFileSync(self.inputFile, includePaths),
        paths: includePaths,
      };

      _.merge(lessOptions, self.lessOptions);
      lessOptions.paths = [path.dirname(lessOptions.filename)].concat(lessOptions.paths);
      data = fs.readFileSync(lessOptions.filename, 'utf8');

      var parser = new(less.Parser)(lessOptions);

      var promise = new RSVP.Promise(function(resolve, reject) {
        parser.parse(data, function (e, tree) {
          try {
            if (e) {
              less.writeError(e, lessOptions);
              reject(e);
            }

            var css = tree.toCSS(lessOptions);
            fs.writeFileSync(destFile, css, {
              encoding: 'utf8'
            });

            resolve(self._tmpDestDir);
          } catch(error) {
            reject(error);
          }
        });
      });

      return promise;
    });
};