easel/tapir

Declarative, type-safe web endpoints library

Welcome!

Intro

With tapir, you can describe HTTP API endpoints as immutable Scala values. Each endpoint can contain a number of input and 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]
  • Netty
  • Finatra FinatraRoute
  • Pekko HTTP Routes/Directives
  • Play Route
  • Vert.X Router => Route
  • ZIO Http Http
  • Armeria HttpServiceWithRoutes
  • aws through Lambda/SAM/Terraform
• a client, which is a function from input parameters to output parameters. Currently supported:
  • sttp
  • Play
  • http4s
• documentation. Currently supported:
  • OpenAPI
  • AsyncAPI

Depending on how you prefer to explore the library, take a look at one of the examples or head over to the docs for a more detailed description of how tapir works! Or, use adopt-tapir to generate a tapir-based project in a couple of clicks! You can also generate a stub of a tapir-based application directly from the command line with sbt new softwaremill/tapir.g8.

Why tapir?

• type-safety: compile-time guarantees, develop-time completions, read-time information
• declarative: separate the shape of the endpoint (the "what"), from the server logic (the "how")
• OpenAPI / Swagger integration: generate documentation from endpoint descriptions
• observability: leverage the metadata to report rich metrics and tracing information
• abstraction: re-use common endpoint definitions, as well as individual inputs/outputs
• library, not a framework: integrates with your stack

Adopters

Is your company already using tapir? We're continually expanding the "adopters" section in the documentation; the more the merrier! It would be great to feature your company's logo, but in order to do that, we'll need written permission to avoid any legal misunderstandings.

Please email us at tapir@softwaremill.com from your company's email with a link to your logo (if we can use it, of course!) or with details who to kindly ask for permission to feature the logo in tapir's documentation. We'll handle the rest.

Teaser

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

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


// Define an endpoint

val booksListing: PublicEndpoint[(BooksQuery, Limit, AuthToken), String, List[Book], Any] = 
  endpoint
    .get
    .in(("books" / path[String]("genre") / path[Int]("year")).mapTo[BooksQuery])
    .in(query[Limit]("limit").description("Maximum number of books to retrieve"))
    .in(header[AuthToken]("X-Auth-Token"))
    .errorOut(stringBody)
    .out(jsonBody[List[Book]])


// Generate OpenAPI documentation

import sttp.apispec.openapi.circe.yaml._
import sttp.tapir.docs.openapi.OpenAPIDocsInterpreter

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


// Convert to akka-http Route

import sttp.tapir.server.akkahttp.AkkaHttpServerInterpreter
import akka.http.scaladsl.server.Route
import scala.concurrent.Future
import scala.concurrent.ExecutionContext.Implicits.global

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


// Convert to sttp Request

import sttp.tapir.client.sttp.SttpClientInterpreter
import sttp.client3._

val booksListingRequest: Request[DecodeResult[Either[String, List[Book]]], Any] = 
  SttpClientInterpreter()
    .toRequest(booksListing, Some(uri"http://localhost:8080"))
    .apply((BooksQuery("SF", 2016), 20, "xyz-abc-123"))

Documentation

tapir documentation is available at tapir.softwaremill.com.

Quickstart with sbt

Add the following dependency:

"com.softwaremill.sttp.tapir" %% "tapir-core" % "1.9.7"

Then, import:

import sttp.tapir._

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

Scala 2.12

Partial unification is now enabled by default from Scala 2.13. However, if you're using Scala 2.12 or older, then you'll need partial unification enabled in the compiler (alternatively, you'll need to manually provide type arguments in some cases):

scalacOptions += "-Ypartial-unification"

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

Other sttp projects

sttp is a family of Scala HTTP-related projects, and currently includes:

• sttp client: the Scala HTTP client you always wanted!
• sttp tapir: this project
• sttp model: simple HTTP model classes (used by client & tapir)
• sttp shared: shared web socket, FP abstractions, capabilities and streaming code.
• sttp apispec: OpenAPI, AsyncAPI and JSON Schema models.

Contributing

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 discourse or via github. This probably means that the documentation, scaladocs or code is unclear and be improved for the benefit of all. In order to develop the documentation, you can use the doc/watch.sh script, which runs Sphinx using Python. Use doc/requirements.txt to set up your Python environment with pip. If you're using Nix, you can just run nix develop in the doc directory to set up a working shell with all the dependencies.

The core module needs to remain binary-compatible with earlier versions. To check if your changes meet this requirement, you can run core/mimaReportBinaryIssues from the sbt console. However, be aware that tags from the repository aren’t automatically fetched during forking; hence, the command will not operate without first fetching the tags.

After forking and cloning the repository, add the original repository as a remote:

git remote add upstream git@github.com:softwaremill/tapir.git

Fetch the tags from the upstream:

git fetch --tags upstream

Scoping which projects are included by sbt

• when STTP_NATIVE is set, Scala native projects are included in the build (when running sbt)
• when ALSO_LOOM is set, projects using virtual threads and requiring Java 21 are included in the build
• when ONLY_LOOM is set, only projects using virtual threads are included in the build

Testing locally

The JS tests use Gecko instead of Chrome, although this causes another problem: out of memory when running JS tests for multiple modules. Work-arounds:

• run only tests for a specific Scala version and platform using testScoped 2.13 JS (supported versions: 2.12, 2.13, 3; supported platforms: JVM, JS, Native)
• test single JS projects
• use CI (GitHub Actions) to test all projects - the .github/workflows/ci.yml enumerates them one by one

You can test only server/client/doc/other projects using testServers, testClients, testDocs and testOther.

To verify that the code snippet in docs compile, run compileDocumentation. A full mdoc run is done during a release (when the documentation is generated).

Importing into IntelliJ

By default, when importing to IntelliJ, only the Scala 3/JVM subprojects will be imported. This is controlled by the ideSkipProject setting in build.sbt (inside commonSettings).

If you'd like to work on a different platform or Scala version, simply change this setting temporarily so that the correct subprojects are imported. For example:

// import only Scala 2.13, JS projects
ideSkipProject := (scalaVersion.value != scala2_13) || !thisProjectRef.value.project.contains("JS")

// import only Scala 3, JVM projects
ideSkipProject := (scalaVersion.value != scala3) || thisProjectRef.value.project.contains("JS") || thisProjectRef.value.project.contains("Native"),

// import only Scala 2.13, Native projects
ideSkipProject := (scalaVersion.value != scala2_13) || !thisProjectRef.value.project.contains("Native")

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) 2018-2023 SoftwareMill https://softwaremill.com.