index.js

var fs = require('fs')
var spawn = require('child_process').spawn
var path = require('path')
var getOptions = require('loader-utils').getOptions
var defaults = require('lodash.defaults')
var util = require('util')

function pushAll (dest, src) {
  Array.prototype.push.apply(dest, src)
}

/* Create a delimeter that is unlikely to appear in parsed code. I've split this
 * string deliberately in case this file accidentally ends up being transpiled
 */
var ioDelimiter = '_' + '_RAILS_ERB_LOADER_DELIMETER__'

/* Match any block comments that start with the string `rails-erb-loader-`. */
var configCommentRegex = /\/\*\s*rails-erb-loader-([a-z-]*)\s*([\s\S]*?)\s*\*\//g

/* Absolute path to the Ruby script that does the ERB transformation. */
var runnerPath = path.join(__dirname, 'erb_transformer.rb')

/* Takes a path and attaches `.rb` if it has no extension nor trailing slash. */
function defaultFileExtension (dependency) {
  return /((\.\w*)|\/)$/.test(dependency) ? dependency : dependency + '.rb'
}

/* Split the `runner` string into a `.file` and its `.arguments` */
function parseRunner (runner) {
  var runnerArguments = runner.split(' ')
  var runnerFile = runnerArguments.shift()

  return { file: runnerFile, arguments: runnerArguments }
}

/* Get each space separated path, ignoring any empty strings. */
function parseDependenciesList (root, string) {
  return string.split(/\s+/).reduce(function (accumulator, dependency) {
    if (dependency.length > 0) {
      var absolutePath = path.resolve(root, defaultFileExtension(dependency))
      accumulator.push(absolutePath)
    }
    return accumulator
  }, [])
}

/* Update config object in place with comments from file */
function parseDependencies (source, root) {
  var dependencies = []
  var match = null
  while ((match = configCommentRegex.exec(source))) {
    var option = match[1]
    var value = match[2]
    switch (option) {
      case 'dependency':
      case 'dependencies':
        pushAll(dependencies, parseDependenciesList(root, value))
        break
      default:
        console.warn(
          'WARNING: Unrecognized configuration command ' +
          '"rails-erb-loader-' + option + '". Comment ignored.'
        )
    }
  }
  return dependencies
}

/* Launch Rails in a child process and run the `erb_transformer.rb` script to
 * output transformed source.
 */
function transformSource (runner, config, source, map, callback) {
  var callbackCalled = false
  var subprocessOptions = {
    stdio: ['pipe', 'pipe', process.stderr],
    env: config.env
  }

  var child = spawn(
    runner.file,
    runner.arguments.concat(
      `"${runnerPath}"`,
      ioDelimiter,
      config.engine
    ),
    subprocessOptions
  )
  var timeoutId = config.timeoutMs
    ? setTimeout(function () { child.kill() }, config.timeoutMs)
    : -1

  var dataBuffers = []
  child.stdout.on('data', function (data) {
    if (config.debug) { console.log(data) }
    dataBuffers.push(data)
  })

  // NOTE: From 'exit' event docs (assumed to apply to 'close' event)
  //
  // "If the process exited, code is the final exit code of the process,
  // otherwise null. If the process terminated due to receipt of a signal,
  // signal is the string name of the signal, otherwise null. One of the two
  // will always be non-null."
  //
  // see: https://nodejs.org/api/child_process.html#child_process_event_exit
  child.on('close', function (code, signal) {
    if (callbackCalled) return

    if (code === 0) {
      // Output is delimited to filter out unwanted warnings or other output
      // that we don't want in our files.
      var sourceRegex = new RegExp(ioDelimiter + '([\\s\\S]+)' + ioDelimiter)
      var matches = Buffer.concat(dataBuffers).toString().match(sourceRegex)
      var transformedSource = matches && matches[1]
      if (timeoutId !== -1) {
        clearTimeout(timeoutId)
      }
      callback(null, transformedSource, map)
    } else if (child.killed) {
      // `child.killed` is true only if the process was killed by `ChildProcess#kill`,
      // ie. after a timeout.
      callback(new Error(
        'rails-erb-loader took longer than the specified ' + config.timeoutMs +
        'ms timeout'
      ))
    } else if (signal !== null) {
      callback(new Error('rails-erb-loader was terminated with signal: ' + signal))
    } else {
      callback(new Error('rails-erb-loader failed with code: ' + code))
    }

    callbackCalled = true
  })

  child.on('error', function (error) {
    if (callbackCalled) return

    callback(error)
    callbackCalled = true
  })

  child.stdin.on('error', function (error) {
    console.error(
      'rails-erb-loader encountered an unexpected error while writing to stdin: "' +
      error.message + '". Please report this to the maintainers.'
    )
  })
  child.stdin.write(source)
  child.stdin.end()
}

function addDependencies (loader, paths, callback) {
  var remaining = paths.length

  if (remaining === 0) callback(null)

  paths.forEach(function (path) {
    fs.stat(path, function (error, stats) {
      if (error) {
        if (error.code === 'ENOENT') {
          callback(new Error('Could not find dependency "' + path + '"'))
        } else {
          callback(error)
        }
      } else {
        if (stats.isFile()) {
          loader.addDependency(path)
        } else if (stats.isDirectory()) {
          loader.addContextDependency(path)
        } else {
          console.warning(
            'rails-erb-loader ignored dependency that was neither a file nor a directory'
          )
        }
        remaining--
        if (remaining === 0) callback(null)
      }
    })
  })
}

var setTimeoutMsFromTimeoutInPlace = util.deprecate(function (config) {
  if (config.timeoutMs != null) {
    throw new TypeError(
      'Both options `timeout` and `timeoutMs` were set -- please just use ' +
      '`timeoutMs`'
    )
  }
  config.timeoutMs = config.timeout * 1000
  delete config.timeout
}, 'rails-erb-loader `timeout` option is deprecated in favor of `timeoutMs`')

module.exports = function railsErbLoader (source, map) {
  var loader = this

  // Mark loader cacheable. Must be called explicitly in webpack 1.
  // see: https://webpack.js.org/guides/migrating/#cacheable
  loader.cacheable()

  // Get options passed in the loader query, or use defaults.
  // Modifying the return value of `getOptions` is not permitted.
  var config = defaults({}, getOptions(loader), {
    dependenciesRoot: 'app',
    runner: './bin/rails runner',
    engine: 'erb',
    env: process.env,
    debug: false
  })

  if (config.timeout !== undefined) {
    setTimeoutMsFromTimeoutInPlace(config)
  }

  // Dependencies are only useful in development, so don't bother searching the
  // file for them otherwise.
  var dependencies = process.env.NODE_ENV === 'development'
    ? parseDependencies(source, config.dependenciesRoot)
    : []

  // Parse the runner string before passing it down to `transfromSource`
  var runner = parseRunner(config.runner)

  var callback = loader.async()

  // Register watchers for any dependencies.
  addDependencies(loader, dependencies, function (error) {
    if (error) {
      callback(error)
    } else {
      transformSource(runner, config, source, map, callback)
    }
  })
}