source: Dev/trunk/node_modules/grunt-contrib-less/tasks/less.js @ 484

/*
 * grunt-contrib-less
 * http://gruntjs.com/
 *
 * Copyright (c) 2013 Tyler Kellen, contributors
 * Licensed under the MIT license.
 */

'use strict';

module.exports = function(grunt) {

  // Internal lib.
  var contrib = require('grunt-lib-contrib').init(grunt);

  var path = require('path');
  var less = require('less');

  var lessOptions = {
    parse: ['paths', 'optimization', 'filename', 'strictImports', 'syncImport', 'dumpLineNumbers', 'relativeUrls', 'rootpath'],
    render: ['compress', 'yuicompress', 'ieCompat', 'strictMath']
  };

  grunt.registerMultiTask('less', 'Compile LESS files to CSS', function() {
    var done = this.async();

    var options = this.options();
    grunt.verbose.writeflags(options, 'Options');

    if (this.files.length < 1) {
      grunt.log.warn('Destination not written because no source files were provided.');
    }

    grunt.util.async.forEachSeries(this.files, function(f, nextFileObj) {
      var destFile = f.dest;

      var files = f.src.filter(function(filepath) {
        // Warn on and remove invalid source files (if nonull was set).
        if (!grunt.file.exists(filepath)) {
          grunt.log.warn('Source file "' + filepath + '" not found.');
          return false;
        } else {
          return true;
        }
      });

      if (files.length === 0) {
        if (f.src.length < 1) {
          grunt.log.warn('Destination not written because no source files were found.');
        }

        // No src files, goto next target. Warn would have been issued above.
        return nextFileObj();
      }

      var compiledMax = [], compiledMin = [];
      grunt.util.async.concatSeries(files, function(file, next) {
        compileLess(file, options, function(css, err) {
          if (!err) {
            if (css.max) {
              compiledMax.push(css.max);
            }
            compiledMin.push(css.min);
            next();
          } else {
            nextFileObj(err);
          }
        });
      }, function() {
        if (compiledMin.length < 1) {
          grunt.log.warn('Destination not written because compiled files were empty.');
        } else {
          var min = compiledMin.join(options.yuicompress ? '' : grunt.util.normalizelf(grunt.util.linefeed));
          grunt.file.write(destFile, min);
          grunt.log.writeln('File ' + destFile.cyan + ' created.');

          // ...and report some size information.
          if (options.report) {
            contrib.minMaxInfo(min, compiledMax.join(grunt.util.normalizelf(grunt.util.linefeed)), options.report);
          }
        }
        nextFileObj();
      });

    }, done);
  });

  var compileLess = function(srcFile, options, callback) {
    options = grunt.util._.extend({filename: srcFile}, options);
    options.paths = options.paths || [path.dirname(srcFile)];

    var css;
    var srcCode = grunt.file.read(srcFile);

    var parser = new less.Parser(grunt.util._.pick(options, lessOptions.parse));

    parser.parse(srcCode, function(parse_err, tree) {
      if (parse_err) {
        lessError(parse_err);
        callback('',true);
      }

      try {
        css = minify(tree, grunt.util._.pick(options, lessOptions.render));
        callback(css, null);
      } catch (e) {
        lessError(e);
        callback(css, true);
      }
    });
  };

  var formatLessError = function(e) {
    var pos = '[' + 'L' + e.line + ':' + ('C' + e.column) + ']';
    return e.filename + ': ' + pos + ' ' + e.message;
  };

  var lessError = function(e) {
    var message = less.formatError ? less.formatError(e) : formatLessError(e);

    grunt.log.error(message);
    grunt.fail.warn('Error compiling LESS.');
  };

  var minify = function (tree, options) {
    var result = {
      min: tree.toCSS(options)
    };
    if (!grunt.util._.isEmpty(options)) {
      result.max = tree.toCSS();
    }
    return result;
  };
};