Play framework 2.3 ActionBuilder composition issue - scala

Question

I really like play framework 2.3's ActionBuilder and the andThen method that allows you to dynamically compose actions.
Here's a snippet of how I want to use action composition:
def showHomepage = RedirectingAction andThen
AuthenticatedAction andThen NotificationAction async { request =>
Future {
Ok(views.html.homepage.render(request.user, request.notifications ))
}
}
As you can guess, NotificationAction depends on AuthenticatedAction, and hence needs AuthenticatedRequest which contains the User object.
The code complains on:
object NotificationAction extends ActionBuilder[NotificationAuthRequest] {
def invokeBlock[A](request: AuthenticatedRequest[A], block: (NotificationAuthRequest[A]) => Future[Result]) = { ...
The error is:
object creation impossible, since method invokeBlock in trait ActionFunction of type [A](request: play.api.mvc.Request[A], block: controllers.v3.ScalaHomepageController.NotificationAuthRequest[A] => scala.concurrent.Future[play.api.mvc.Result])scala.concurrent.Future[play.api.mvc.Result] is not defined
Apparently it allows only:
def invokeBlock[A](request: Request[A], block: ...
but not:
def invokeBlock[A](request: AuthenticatedRequest[A], block: ...
I'd really appreciate if someone could throw light on this. Maybe my approach is wrong, but I don't like the idea of precomposed actions (like using ActionFunction) because I could have more actions that I could be mixing in at a later point.
Here's the code:
case class AuthenticatedRequest[A](val user: Option[User], request: Request[A]) extends WrappedRequest(request)
case class NotificationAuthRequest[A](val user: Option[User], val notifications: Option[List[UserNotificationData]], request: Request[A]) extends WrappedRequest(request)
object RedirectingAction extends ActionBuilder[Request] {
def invokeBlock[A](request: Request[A], block: (Request[A]) => Future[Result]) = {
Future {
Redirect(REDIRECT_URL + request.uri + paramString)
}
}
}
object AuthenticatedAction extends ActionBuilder[AuthenticatedRequest] {
def invokeBlock[A](request: Request[A], block: (AuthenticatedRequest[A]) => Future[Result]) = {
request.cookies.get("uid") map {
cookie =>
val user = userClient.getUserById(userId(cookie)).get
block(AuthenticatedRequest[A](user, request))
} getOrElse {
block(AuthenticatedRequest[A](userClient.getUserById(uid).get, request))
}
}
def userId(cookie: Cookie) = {
if(AppUtil.isProd) cookie.value else IMPERSONATE_ID.getOrElse(cookie.value)
}
}
object NotificationAction extends ActionBuilder[NotificationAuthRequest] {
def invokeBlock[A](request: AuthenticatedRequest[A], block: (NotificationAuthRequest[A]) => Future[Result]) = {
request.user.map {
user => block(NotificationAuthRequest[A](Some(user), userClient.getNotifications(user.getId).get.map(_.toList), request))
}.getOrElse {
block(NotificationAuthRequest[A](None, None, request))
}
}
}

Answer 1

Reading the docs I think you need to have ActionRefiners and ActionTransformers.
This is what I came up with:
package controllers
import play.api.mvc._
import scala.concurrent.Future
case class User(id: Long)
case class UserNotificationData(text: String)
case class AuthRequest[A](user: Option[User], request: Request[A]) extends WrappedRequest(request)
case class AuthNotificationRequest[A](user: Option[User], notifications: Option[List[UserNotificationData]], request: Request[A]) extends WrappedRequest(request)
object RedirectingAction extends ActionBuilder[Request] {
def invokeBlock[A](request: Request[A], block: (Request[A]) => Future[Result]) = {
block(request)
}
}
object AuthenticatedAction extends ActionBuilder[AuthRequest] with ActionTransformer[Request, AuthRequest] {
def transform[A](request: Request[A]) = Future.successful {
request.cookies.get("uid") map {
cookie =>
val user = Some(User(1))
AuthRequest[A](user, request)
} getOrElse {
AuthRequest[A](Some(User(1)), request)
}
}
}
object WithNotifications extends ActionTransformer[AuthRequest, AuthNotificationRequest] {
def transform[A](request: AuthRequest[A]) = Future.successful {
request.user.map { user => AuthNotificationRequest[A](Some(user), Some(List(UserNotificationData("Notification"))), request)} getOrElse {
AuthNotificationRequest[A](None, None, request)
}
}
}
object Application extends Controller {
def index = (RedirectingAction andThen AuthenticatedAction andThen WithNotifications) { request: AuthNotificationRequest[AnyContent] =>
Ok(views.html.index("Your new application is ready."))
}
}