index.js

var exec = require('child_process').exec;
var through = require('through2');
var gutil = require('gulp-util');
var merge = require('merge');
var PluginError = gutil.PluginError;
var chalk = require('chalk');
var winston = require('winston');
var vnuJar = require('vnu-jar');

var vnuErrorLevels = {
  levels: {
    'success': 0,
    'error': 1,
    'info': 2,
    'non-document-error': 3
  },
  colors: {
    'success': 'green',
    'error': 'red',
    'info': 'yellow',
    'non-document-error': 'black'
  }
};

const logger = new (winston.Logger)({
  levels: vnuErrorLevels.levels,
  transports: [
    new (winston.transports.Console)({
      formatter: function(options) {
        var levelType = '';
        // Return string will be passed to logger.
        if(options.level === 'error') {
          levelType = chalk.red('error: ');
        }
        else if(options.level === 'info') {
          levelType = chalk.yellow('warning: ');
        }
        else if(options.level === 'success') {
          return chalk.green(options.message) + chalk.underline.bold(options.meta.path) + '\n';
        }
        else {
          return chalk.bold('non-document-error: ') + options.message;
        }

        return  levelType + chalk.underline.bold(options.meta.url) + '\n' +
          chalk.bold(options.meta.lastLine + ':' + options.meta.firstColumn) + '\t' + options.message + '\n' +
          'source: ' + options.meta.extract + '\n';
      }
    })
  ]
});

module.exports = function(opt) {
  var vnuCmd = 'java -Xss1024k -jar ' + vnuJar + ' ';

  var options = merge({
    'errors-only': false,
    'format': 'gnu',
    'html': false,
    'no-stream': false,
    'verbose': false
  }, opt);

  // Set options
  Object.keys(options).forEach(function (key) {
    var val = options[key];
    if (key === 'format' && val !== 'gnu') vnuCmd += '--format ' + val + ' ';
    if (val === true) vnuCmd += '--' + key + ' ';
  });

  function handleError (error, messages, path) {
    var parsedMessages = JSON.parse(messages).messages;

    if(error === null && !parsedMessages.length) {
      logger.log('success', 'Document is valid: ', {path: path});
    }
    else {
      parsedMessages.map(function(msg) {
        logger.log(msg.type, msg.message, msg);
      });
    }
  }

  var stream  = through.obj(function(file, enc, cb) {
    if (file.isNull()) return cb(null, file);
    if (file.isStream()) {
      return cb(new PluginError('gulp-html', 'Streaming not supported'));
    }

    exec(vnuCmd + file.history, function (err, stdout, stderr) {
      if(options.format === 'json') {
        return cb(handleError(err, stderr, file.history[0]));
      }

      if (err === null) return cb(null, file);
      return cb(new PluginError('gulp-html', stderr));
    });
  });

  return stream;
};