Example: respond with 404 if None returned from server logic (#4257)

examples/src/main/scala/sttp/tapir/examples/errors/optionalValueExample.scala

@@ -0,0 +1,65 @@
+// {cat=Error handling; effects=Future; server=Pekko HTTP; JSON=circe}: Optional returned from the server logic, resulting in 404 if None
+
+//> using dep com.softwaremill.sttp.tapir::tapir-core:1.11.12
+//> using dep com.softwaremill.sttp.tapir::tapir-pekko-http-server:1.11.12
+//> using dep com.softwaremill.sttp.tapir::tapir-json-circe:1.11.12
+//> using dep com.softwaremill.sttp.client3::core:3.10.2
+
+package sttp.tapir.examples.errors
+
+import io.circe.generic.auto.*
+import io.circe.parser.parse
+import org.apache.pekko.actor.ActorSystem
+import org.apache.pekko.http.scaladsl.Http
+import sttp.client3.{HttpURLConnectionBackend, Identity, SttpBackend, UriContext, basicRequest}
+import sttp.model.StatusCode
+import sttp.tapir.*
+import sttp.tapir.generic.auto.*
+import sttp.tapir.json.circe.*
+import sttp.tapir.server.pekkohttp.PekkoHttpServerInterpreter
+
+import scala.concurrent.{Await, Future}
+import scala.concurrent.duration.*
+
+@main def optionalValueExample(): Unit =
+
+  case class Beer(name: String, volumeInLiters: Double)
+
+  val bartenderEndpoint = endpoint
+    .get
+    .in("beer" / query[Int]("age"))
+    // Optional value from serverLogic, responding with 404 "Not Found" when logic returns None
+    .out(oneOf(
+      oneOfVariantExactMatcher(StatusCode.NotFound, jsonBody[Option[Beer]])(None),
+      oneOfVariantValueMatcher(StatusCode.Ok, jsonBody[Option[Beer]]) {
+        case Some(_) => true
+      }
+    ))
+
+  //
+
+  val bartenderServerEndpoint = bartenderEndpoint.serverLogic {
+      case a if a < 18 => Future.successful(Right(None))
+      case _ => Future.successful(Right(Some(Beer("IPA", 0.5))))
+    }
+
+
+  given actorSystem: ActorSystem = ActorSystem()
+  import actorSystem.dispatcher
+  val routes = PekkoHttpServerInterpreter().toRoute(bartenderServerEndpoint)
+
+  val serverBinding = Http().newServerAt("localhost", 8080).bindFlow(routes).map { binding =>
+    val backend: SttpBackend[Identity, Any] = HttpURLConnectionBackend()
+
+    val response1 = basicRequest.get(uri"http://localhost:8080/beer?age=15").send(backend)
+    assert(response1.code == StatusCode.NotFound)
+
+    val response2 = basicRequest.get(uri"http://localhost:8080/beer?age=21").send(backend)
+    println("Got result: " + response2.body)
+    val beerEither = response2.body.flatMap(parse).flatMap(_.as[Beer])
+    assert(beerEither == Right(Beer("IPA", 0.5)))
+
+    binding
+  }
+
+  val _ = Await.result(serverBinding, 1.minute)