[BUG] SwaggerAkka can't be used with a path of more than one segment

[kubukoz]

Tapir version: 0.16.10

Scala version: 2.12.12

Describe the bug

val path = "v1/docs"

new SwaggerAkka(docs.toYaml, path).routes

Using a route generated like that results in an invalid route: it doesn't match /v1/docs, but actually /v1/%2Fdocs (%2F, the urlencoded slash) - that's because SwaggerAkka is using pathPrefix(path) which accepts a PathMatcher, to which the string is converted as an entire segment.

When you go to /v1/%2Fdocs, however, you get a redirect to /v1/docs/index.html?url=/v1/docs/docs.yaml, which is still incorrect:

url --head localhost:8080/v1%2Fdocs                                                      
HTTP/1.1 308 Permanent Redirect
Location: /v1/docs/index.html?url=/v1/docs/docs.yaml
Server: akka-http/10.1.12
Date: Wed, 05 Aug 2020 23:33:26 GMT
Content-Type: text/html; charset=UTF-8
Content-Length: 128

How to reproduce?

libraryDependencies ++= Seq(
  "com.softwaremill.sttp.tapir" %% "tapir-akka-http-server" % "0.16.10",
  "com.softwaremill.sttp.tapir" %% "tapir-openapi-docs" % "0.16.10",
  "com.softwaremill.sttp.tapir" %% "tapir-openapi-circe-yaml" % "0.16.10",
  "com.softwaremill.sttp.tapir" %% "tapir-swagger-ui-akka-http" % "0.16.10"
)

scalaVersion := "2.12.12"

import java.nio.charset.StandardCharsets
import sttp.tapir.openapi.circe.yaml._
import sttp.tapir.openapi._
import sttp.tapir.docs.openapi._
import akka.http.scaladsl.Http
import akka.http.scaladsl.server.Directives
import akka.actor.ActorSystem
import akka.http.scaladsl.server.HttpApp
import sttp.tapir.swagger.akkahttp.SwaggerAkka
import sttp.tapir.server.akkahttp._
import scala.concurrent.Future

object Endpoints {
  import sttp.tapir._

  val randomEndpoint: Endpoint[Unit, Unit, String, Nothing] =
    endpoint.in("v1" / "hello").out(stringBody(StandardCharsets.UTF_8))

}
object Demo extends HttpApp with App {

  import Endpoints._

  val docs =
    randomEndpoint
      .toOpenAPI("my app", "0.0.1")

  val docsRoute = new SwaggerAkka(docs.toYaml, "v1/docs").routes
  val route = randomEndpoint.toRoute(_ => Future.successful(Right("witam")))

  override val routes = docsRoute // ~ route

  startServer("localhost", 8080)
}

then hit localhost:8080/v1/docs in your browser.

Additional information

This has been encountered by @CucumisSativus, so credits to him for finding this issue ;)

I think the simplest fix would be to either:

• accept some PathMatcher[...] instead of a String (might be weird in types, haven't tried though)
• not accept any string at all and create a route on the root level, thus requiring users to wrap the whole thing in a pathPrefix of their own
• accept a list of segments and concatenate them with the right / operator.

I would personally opt for option 2, as it's the most flexible anyway. The existing implementation could be left as a deprecated overload for a while, then removed maybe in 0.17 or 1.0.