Scala 3 opaque types are not supported as path parameters

[colin-lamed]

Play Version

3.0.3

API

Scala

Expected Behavior

For an opaque type with PathBindable, e.g.

opaque type TeamName = String

implicit def teamNamePathBindable(using strBinder: PathBindable[String]): PathBindable[TeamName] =
    strBinder.transform(TeamName.apply, _.toString())

and a Controller

@Singleton
class TeamsController @Inject()(cc: ControllerComponents) extends AbstractController(cc) {
  def team(teamName: TeamName): Action[AnyContent] =
    Action { OK("Hello " + teamName) }
}

When creating a route with the path bindable, e.g.

GET        /teams/:teamName  TeamsController.team(teamName: TeamName)

It should generate a Routes file for this endpoint

Actual Behavior

The compiler throws

[error] /conf/app.routes:5:1: model.TeamName is not a class type
[error] GET        /teams/:teamName    TeamsController.team(teamName: TeamName)
[error] one error found
[error] (Compile / compileIncremental) Compilation failed

Note, this can be implemented when providing the generated routes manually when the HandlerDef. parameterTypes are suppressed:

override def routes: Router.Routes = {
    case routeMatch(params@_) =>
      call(params.fromPath[TeamName]("teamName", None)) { (teamName) =>
        createInvoker(
          fakeCall   = teamsController.team(fakeValue[TeamName]),
          handlerDef = HandlerDef(
            classLoader    = this.getClass.getClassLoader,
            routerPackage  = "app",
            controller     = "TeamsController",
            method         = "team",
            parameterTypes = Seq.empty,//Seq(classOf[TeamName]), // This is where opaque types don't work
            verb           = "GET",
            path           = this.prefix + """teams/""" + "$" + """teamName<[^/]+>/team""",
            comments       = "",
            modifiers      = Seq.empty
          )
        ).call(teamsController.team(teamName))
      }
  }

  private lazy val routeMatch = Route("GET",
    PathPattern(List(StaticPart(this.prefix), StaticPart(this.defaultPrefix), StaticPart("teams/"), DynamicPart("teamName", """[^/]+""", encodeable=true), StaticPart("/team")))
  )

[mkurz]

hmm.... I will not work on this right now, not sure yet if/what we can do on Play's side here. If you come up with a PR of course I am happy to review it.

[AndySpaven]

Looking at https://github.com/playframework/playframework/blob/03149e7f022e12b70eda882a85c9ca5768748b2a/dev-mode/play-routes-compiler/src/main/twirl/play/routes/compiler/inject/forwardsRouter.scala.twirl#L68 the problem is with classOf[SomeOpaqueType]. I've found a possible fix in the routes file but not sure where else opaque types may fail. Hence this isn't a PR.

@call.parameters.filterNot(_.isEmpty).map(params => params.map("classOf[" + _.typeNameReal + "]").mkString(", ")).map("Seq(" + _ + ")").getOrElse("Nil"), becomes

@call.parameters.filterNot(_.isEmpty).map(params => params.map("scala.reflect.classTag[" + _.typeNameReal + "].runtimeClass").mkString(", ")).map("Seq(" + _ + ")").getOrElse("Nil"),

This translates the opaque type to it's underlying class rather than trying to get the class directly and seems to work for cases that broke with it as it was.