Browserify Transformer for Nunjucks Templates

nunjucksify.js

var through = require('through'),
  path = require('path'),
  nunjucks = require('nunjucks'),
  appRootPath = require('app-root-path').path,
  _ = require('underscore');

var getTemplateReg = /env\.getTemplate\(("(.*?)")/g;

/**
 * Calculates the templates path relative to the app root path.
 */
function templatePath(templatePath) {
  return path.relative(appRootPath, templatePath);
}

/**
 * Browserify transformer for nunjucks templates
 */
function nunjucksify(file, options) {
  var data, extension;

  options = options || {};
  extension = options.extension || ['.nunj'];

  if (!Array.isArray(extension))
    extension = [extension];

  // Check for nunjucks template extension for skipping other content types
  if (!_.contains(extension, path.extname(file)))
    return through();

  // The options hash gets directly passed to the nunjucks.precompileString function.
  // The name option must be fixed to be unique in the precompiling process.
  options = _.extend({
    asFunction: true
  }, options, {
    name: templatePath(file)
  });

  data = '';

  function write(buf) {
    data += buf;
  }

  function buildModule(compiledTemplate) {
    var module = [], requiredTemplates, requires;

    if (options.asFunction) {
      requiredTemplates = {};

      // options.asFunction is true, so we need the nunjucks module for rendering inside the built module
      module.push('var nunjucks = require(\'nunjucks\');');

      compiledTemplate = compiledTemplate.replace(getTemplateReg, function(fullMatch, strMatch, pathMatch) {
        var resolvedTemplatePath = templatePath(path.resolve(path.dirname(file), pathMatch));

        // Store the template paths in the requiredPaths data set for later use.
        requiredTemplates[resolvedTemplatePath] = pathMatch;

        // Replace the getTemplate function call parameter (template file path) with our unique template path.
        return fullMatch.replace(pathMatch, resolvedTemplatePath);
      });

      // Build the require statements for the needed templates to be known to browserify.
      requires = _.values(requiredTemplates).map(function(path) {
        return 'require(\'' + path + '\');';
      });

      // Do we have any required templates? Add them as simple statements to the generated module.
      if (requires.length > 0)
        module.push.apply(module, requires);

      module.push(compiledTemplate);
    } else {
      compiledTemplate = compiledTemplate.replace(getTemplateReg, function(fullMatch, strMatch) {
        return fullMatch.replace(strMatch, 'require(' + strMatch + ')');
      });

      // options.asFunction is false, so we need to return the absolute template name to be able to use it inside
      // other modules
      module.push(compiledTemplate);
      module.push('module.exports = \'' + options.name + '\';');
    }

    return module.join('\n');
  }

  function end() {
    var template = nunjucks.precompileString(data, options);

    this.queue(buildModule(template));
    this.queue(null);
  }

  return through(write, end);
}

module.exports = nunjucksify;