Separating CoreDsl from ScalatraBase

[Pyppe]

Would it be possible to separate CoreDsl from the ScalatraBase? This would make it possible to define own typesasfe DSL for the HTTP verbs? (Something like def get(transformers: RouteTransformer*)(block: => MyTypesafeResult): Route)

Why, you ask?

We're refactoring from json4s to argonaut, and like to make it impossible to call e.g. the following:

import JsonImplicits.FooCodecJson
get("/foo") {
  // This compiles but won't produce JSON at runtime,
  // because argonaut cannot do that dynamically (no reflection).
  // Block argument of type `=> Any` is dangerous... :(
  Foo("bar", 5)
}

[dozed]

I am afraid that modifying the DSL (e.g. change the signatures or move the methods out from ScalatraBase) is not possible without breaking existing code. I see three options:

1. Restrict the return type on your own (see below)
2. Create an opt-in solution on which new applications can build for Scalatra 2.x and existing code still runs without modifications.
3. Think how to do this in a Scalatra 3.x, possibly built on http4s.org

You also might want to take a look at https://github.com/ceedubs/scrutinator and https://github.com/ceedubs/scrutinator-pet-store.

import org.scalatra.{ScalatraServlet, ActionResult, Ok}

case class Foo()
case class Bar()

type ResponseRenderer[A] = A => ActionResult

object Renderers {

  def responseRenderer[A](x: ResponseRenderer[A]) = x

  implicit val fooRenderer = responseRenderer[Foo](x => Ok("foo"))

  def restrictTo[A:ResponseRenderer](x: => A): A = x

}

import Renderers._

trait FooServlet extends ScalatraServlet {

  get("/api/foos")(restrictTo[Foo] {
    Foo()
  })

  // does not compile
  get("/api/bars")(restrictTo[Bar] {
    Bar()
  })

}

[takezoe]

@dozed @seratch Should we move this issue to 2.6.0 or 3.0.0 milestone?

[takezoe]

Removed from the milestone once to close 2.5.0 milestone which has been already released. If we should add this to the future plan, set the milestone again, please.