js-module-loader

AMD and CommonJs loaders for Scala.

Setup

resolvers += Resolver.bintrayRepo("dgolubets", "releases")
libraryDependencies += "ru.dgolubets" %% "js-module-loader" % "0.1.1"

AMD

AMD Loader is created as follows

val loader = AmdLoader(FileModuleReader("src/javascript/amd"))

then it can be used in Scala

loader.requireAsync("app").map { module => 
  // module.value will be a ScriptObjectMirror or boxed Java primitive, depending on the module return value
}
loader.requireAsync(Seq("React", "CommentBox")).map {
  case Seq(ScriptModule(react: ScriptObjectMirror), ScriptModule(commentBox: ScriptObjectMirror)) =>
    val commentBoxHtml = loader.lock {
      react.callMember("renderToString", react.callMember("createElement", commentBox)).toString
    }
}

and in Javascript

// javascript should be evaluated with loader.context
loader.engine.eval("require(['app'], function(app){ console.log(app); })")

CommonJs

CommonJs Loader is created as follows

val loader = CommonJsLoader(FileModuleReader("src/javascript/commonjs"))

then it can be used in Scala

loader.require("app") match { 
  case Success(module) => ???
  case _ => ???
}

and in Javascript

// javascript should be evaluated with loader.context
loader.engine.eval("require('app').startMyApp();")

Thread safety

Loaders are safe to use from different threads. However, once you got javascript objects or deal with a ScriptEngine you are one on one with a Nashorn which is not thread safe. You can read more about Nashorn and MT-safety there: https://blogs.oracle.com/nashorn/entry/nashorn_multi_threading_and_mt

To synchronize the loader and external calls to the script engine and script objects there is a special method "lock" on the base interface.

loader.lock {
  // now it's safe to call engine.eval or scriptObjectMirror.callMember
}

Known Issues

Play < 2.4 doesn't have Nashorn classes in it's boot loader. To workaround it, add the following code to your play SBT config

Play.playCommonClassloader := {
  val oldCl = Play.playCommonClassloader.value
  def isNashornClass(className: String) = className.startsWith("jdk.nashorn.")
  def notNashornResource(resource: String) = resource != "META-INF/services/javax.script.ScriptEngineFactory"
  new classpath.DualLoader(
    oldCl, !isNashornClass(_), notNashornResource,
    ClassLoader.getSystemClassLoader, isNashornClass, notNashornResource
  )
}