With tapir you can describe HTTP API endpoints as immutable Scala values. Each endpoint can contain a number of input parameters, error-output parameters, and normal-output parameters. An endpoint specification can be interpreted as:

• a server, given the "business logic": a function, which computes output parameters based on input parameters. Currently supported:
  • Akka HTTP Routes/Directives.
  • Http4s HttpRoutes[F]
• a client, which is a function from input parameters to output parameters. Currently supported: sttp.
• documentation. Currently supported: OpenAPI.

Teaser

import tapir._
import tapir.json.circe._
import io.circe.generic.auto._

type Limit = Int
type AuthToken = String
case class BooksFromYear(genre: String, year: Int)
case class Book(title: String)

val booksListing: Endpoint[(BooksFromYear, Limit, AuthToken), String, List[Book], Nothing] = endpoint
    .get
    .in(("books" / path[String]("genre") / path[Int]("year")).mapTo(BooksFromYear))
    .in(query[Int]("limit").description("Maximum number of books to retrieve"))
    .in(header[String]("X-Auth-Token"))
    .errorOut(stringBody)
    .out(jsonBody[List[Book]])

//

import tapir.docs.openapi._
import tapir.openapi.circe.yaml._

val docs = booksListing.toOpenAPI("My Bookshop", "1.0")
println(docs.toYaml)

//

import tapir.server.akkahttp._
import akka.http.scaladsl.server.Route
import scala.concurrent.Future

def bookListingLogic(bfy: BooksFromYear, 
                     limit: Limit,  
                     at: AuthToken): Future[Either[String, List[Book]]] =
  Future.successful(Right(List(Book("The Sorrows of Young Werther"))))
val booksListingRoute: Route = booksListing.toRoute(bookListingLogic _)

//

import tapir.client.sttp._
import com.softwaremill.sttp._

val booksListingRequest: Request[Either[String, List[Book]], Nothing] = booksListing
  .toSttpRequest(uri"http://localhost:8080")
  .apply(BooksFromYear("SF", 2016), 20, "xyz-abc-123")

Documentation

tapir documentation is available at tapir-scala.readthedocs.io.

Quickstart with sbt

Add the following dependency:

"com.softwaremill.tapir" %% "tapir-core" % "0.11.9"

You'll need partial unification enabled in the compiler (alternatively, you'll need to manually provide type arguments in some cases):

scalacOptions += "-Ypartial-unification"

Then, import:

import tapir._

And finally, type endpoint. and see where auto-complete gets you!

---

Sidenote for scala 2.12.4 and higher: if you encounter an issue with compiling your project because of a StackOverflowException related to this scala bug, please increase your stack memory. Example:

sbt -J-Xss4M clean compile

Contributing

Tapir is an early stage project. Everything might change. All suggestions welcome :)

See the list of issues and pick one! Or report your own.

If you are having doubts on the why or how something works, don't hesitate to ask a question on gitter or via github. This probably means that the documentation, scaladocs or code is unclear and be improved for the benefit of all.

Commercial Support

We offer commercial support for tapir and related technologies, as well as development services. Contact us to learn more about our offer!

Copyright

Copyright (C) 2018-2019 SoftwareMill https://softwaremill.com.