servant-swagger

This project converts servant APIs into Swagger 2.0 conforming json.

Given the following servant API, servant-swagger generates the following json.

Input

{-# LANGUAGE DataKinds                  #-}
{-# LANGUAGE DeriveGeneric              #-}
{-# LANGUAGE GeneralizedNewtypeDeriving #-}
{-# LANGUAGE OverloadedStrings          #-}
{-# LANGUAGE TypeOperators              #-}
module Main where

import Control.Lens
import Data.Aeson
import qualified Data.ByteString.Lazy.Char8 as BL8
import Data.Proxy
import Data.Swagger
import GHC.Generics
import Servant
import Servant.Swagger

-- Types
data Todo = Todo
  { created     :: Int
  , description :: String
  } deriving (Show, Eq, Generic)

instance ToJSON Todo

newtype TodoId = TodoId String deriving (FromText, Generic)

-- API
type API = "todo" :> Capture "id" TodoId :> Get '[JSON] Todo

-- Swagger Doc
swagDoc :: Swagger
swagDoc = toSwagger (Proxy :: Proxy API)
  & info.infoTitle   .~ "Todo API"
  & info.infoVersion .~ "1.0"
  & info.infoDescription ?~ "This is an API that tests servant-swagger support for a Todo"
  & info.infoLicense ?~ License "MIT" (Just (URL "http://mit.com"))

-- Documentation and annotations
instance ToParamSchema TodoId

instance ToSchema Todo where
  declareNamedSchema proxy = do
    (name, schema) <- genericDeclareNamedSchema defaultSchemaOptions proxy
    return (name, schema
      & schemaDescription ?~ "This is some real Todo right here"
      & schemaExample ?~ toJSON (Todo 100 "get milk"))

-- Main, create swaggger.json
main :: IO ()
main = BL8.writeFile "swagger.json" (encode swagDoc)

Output

{
   "swagger":"2.0",
   "info":{
      "version":"1.0",
      "title":"Todo API",
      "license":{
         "url":"http://mit.com",
         "name":"MIT"
      },
      "description":"This is an API that tests servant-swagger support for a Todo"
   },
   "definitions":{
      "Todo":{
         "example":{
            "created":100,
            "description":"get milk"
         },
         "required":[
            "created",
            "description"
         ],
         "type":"object",
         "description":"This is some real Todo right here",
         "properties":{
            "created":{
               "maximum":9223372036854775807,
               "minimum":-9223372036854775808,
               "type":"integer"
            },
            "description":{
               "type":"string"
            }
         }
      }
   },
   "paths":{
      "/todo/{id}":{
         "get":{
            "responses":{
               "404":{
                  "description":"`id` not found"
               },
               "200":{
                  "schema":{
                     "$ref":"#/definitions/Todo"
                  },
                  "description":""
               }
            },
            "produces":[
               "application/json"
            ],
            "parameters":[
               {
                  "required":true,
                  "in":"path",
                  "name":"id",
                  "type":"string"
               }
            ]
         }
      }
   }
}

Try it out

All generated swagger specifications can be interactively viewed on Swagger Editor.

Ready-to-use specification can be served as JSON and interactive API documentation can be displayed using Swagger UI.

Many Swagger tools, including server and client code generation for many languages, can be found on Swagger’s Tools and Integrations page.

Contributing

We are happy to receive bug reports, fixes, documentation enhancements, and other improvements.

Please report bugs via the github issue tracker.