PugJS for Dart by running a node process and communicating over stdio

pug.dart

// Copyright (c) 2017, Herman Bergwerf. All rights reserved.
// Use of this source code is governed by a MIT-style license.

import 'dart:io';
import 'dart:async';
import 'dart:convert';

import 'package:logging/logging.dart';

final log = new Logger('pug');

class PugRenderer {
  Process process;
  final queue = new List<Completer<String>>();

  Future<Null> initialize(String template) async {
    process = await Process.start('node', ['render.js', '$template.pug']);

    process.stderr.listen((data) {
      throw new Exception(
          'Pug renderer experienced an error: ${UTF8.decode(data)}');
    });

    // Listen on stdout.
    process.stdout.listen((data) {
      log.info('Rendered Pug template');
      queue.removeAt(0).complete(UTF8.decode(data));
    });
  }

  Future<String> render(dynamic locals) {
    log.info('Render Pug template');
    final input = JSON.encode(locals);
    final completer = new Completer<String>();
    queue.add(completer);
    process.stdin.writeln(input);
    return completer.future;
  }
}

render.js

// Copyright (c) 2017, Herman Bergwerf. All rights reserved.
// Use of this source code is governed by a MIT-style license.

var fs = require('fs')
var pug = require('pug')
var process = require('process')
var readline = require('readline')

var fileName = process.argv[2]
fs.readFile(fileName, (err, buf) => {
  if (err) {
    throw err
  }
  var str = buf.toString('utf8')
  var fn = pug.compile(str)

  // Start listening on stdin.
  var lineReader = readline.createInterface({
    input: process.openStdin()
  })
  lineReader.on('line', function (line) {
    var json = JSON.parse(line)
    process.stdout.write(fn(json))
  })
})