Jade Syntax Checker

syntax.js

var jade = require('jade'),
    runtime = require('jade/lib/runtime'),
    spawn = require('child_process').spawn,
    fs = require('fs');

function parse(str, filename){
  var options = {filename: filename, compileDebug: true};
  try {
    // Parse
    var parser = new jade.Parser(str, filename, options)
      , compiler = new (jade.Compiler)(parser.parse(), options)
      , js = compiler.compile();
    
    return ''
      + 'var buf = [];\n'
      + js;
  } catch (err) {
    parser = parser.context();
    runtime.rethrow(err, parser.filename, parser.lexer.lineno);
  }
}

function checkSyntax(str, filename) {
  var fn, err, lineno;
  
  fn = ['var __jade = [{ lineno: 1, filename: ' + JSON.stringify(filename) + ' }];'
    , parse(str, filename)].join('\n');
  
  var child = spawn(process.execPath, ['-e', fn]);
  
  child.stderr.setEncoding('utf8');
  
  child.stderr.on('data', function (data) {
    var errLines = data.split('\n'),
        descLine = errLines[4];
    
    if (/^SyntaxError: /.test(descLine)) {
      // Syntax error was found
      var infoLine = errLines[1].split(':');
      
      fn = fn.split('\n').slice(0, infoLine[1]);
      for (var i = 0; i < fn.length; i++)
        if (!/__jade/.test(fn[i]))
          fn[i] = '';
      fn = fn.join('\n') + '__jade[0].lineno';
      lineno = eval(fn);
      
      err = new SyntaxError(descLine.substr(13));
    }
  });
  
  child.on('exit', function (code, signal) {
    if (err)
      runtime.rethrow(err, filename, lineno);
    else
      console.error('No SyntaxError found');
  });
}

function checkFile(path) {
  fs.readFile(path, 'utf8', function (err, str) {
    if (err) throw err;
    checkSyntax(str, path);
  });
}

checkFile('./test.jade');

test.jade

- var o = {a:'Hello', b:'world'}
p= o.a
p= o.b
p(class='foo' id='bar') and fail!

Outputs the following error:

SyntaxError: ./test.jade:4
    2| p= o.a
    3| p= o.b
  > 4| p(class='foo' id='bar') and fail!

Unexpected identifier
    at Socket.<anonymous>
    at Socket.emit (events.js:67:17)
    at Pipe.onread (net.js:342:31)