Show GitHub: An experimental router DSL for warp about warp

[seanmonstar]

This is really cool! (And perhaps somewhat related to #12 and #26).

Something I didn't want to replicate from Akka is the very easy-to-trigger ignored directive since its valid syntax to forget ~. It looks like this doesn't suffer from that.

I haven't built a large app with Akka, but when looking at the examples, it felt like the nested directive style would get very unwieldy with larger and larger apps. Have you noticed that?

[ayosec]

Something I didn't want to replicate from Akka is the very easy-to-trigger ignored directive since its valid syntax to forget ~. It looks like this doesn't suffer from that.

Yep. In Scala it is easier to miss the separator because the ; is optional, so you don't get any help from the compiler. The issue is easier to detect with tests, but still a bit unfortunate.

I haven't built a large app with Akka, but when looking at the examples, it felt like the nested directive style would get very unwieldy with larger and larger apps. Have you noticed that?

You can split the route in multiple functions/files, and put part of its logic in small functions.

Thus, the route tree contains only the declarations to “interpret” the request. The code is also much easier to understand and to maintain.

For example:

// Auth.scala

case class Auth(...) {

  def userAuthenticator(creds: Credentials): Future[Option[User]] = ???

  // Directive to authenticate users
  def requireUser = authenticateBasicAsync(realm = "API", userAuthenticator)

}


// ProjecsAPI.scala

case class ProjecsAPI(...) {

  val auth = Auth()

  def listProjects(user: User) = ???

  def findProject(user: User, projectId: Int): Future[Option[Project]] = ???

  def deleteProject(project: Project): Future[Unit] = ???

  // Routes for /projects

  def routes = pathPrefix("projects") {
    auth.requireUser { user =>
      pathEnd {
        complete(listProjects(user))
      } ~
      path(IntNumber) { projectId =>
        onSuccess(findProject(user, projectId)) {
          case None => 
            complete(NotFound)

          case Some(project) =>
            get {
              complete(project)
            } ~
            delete {
              onSuccess(deleteProject(project)) {
                complete(NoContent)
              }
            }
        }
      }
    }
  }

}


// UsersAPI.scala

case class UsersAPI(...) {

  val auth = Auth()

  // Routes for /users

  def routes = pathPrefix("users") {
    auth.requireUser { user =>
      path("current") {
        complete(user)
      }
    }
  }

}


// Main.scala

val routes = (
  ProjecsAPI().routes ~
  UsersAPI().routes
  // ~ More().routes
)
Http().bindAndHandle(routes, "0.0.0.0", 8080)

(Full example)