servant-http-streams

Automatic derivation of querying functions for servant

http://docs.servant.dev/

LTS Haskell 24.7:	0.20.2@rev:2
Stackage Nightly 2025-08-23:	0.20.2@rev:2
Latest on Hackage:	0.20.2@rev:2

See all snapshots servant-http-streams appears in

BSD-3-Clause licensed by Servant Contributors

Maintained by haskell-servant-maintainers@googlegroups.com

This version can be pinned in stack with:servant-http-streams-0.20.2@sha256:cda06fbc456ff279774f8d3a2fa13f7d47ccb03afb1aea36463b724079b7201d,4525

Module documentation for 0.20.2

Servant
- Servant.HttpStreams
  - Servant.HttpStreams.Internal

Depends on 23 packages(full list with versions):

servant-client

servant

This library lets you automatically derive Haskell functions that let you query each endpoint of a servant webservice.

Example

{-# LANGUAGE DataKinds #-}
{-# LANGUAGE TypeOperators #-}

import Data.Proxy
import Data.Text
import Servant.API
import Servant.HttpStreams


type Book = Text

type MyApi = "books" :> Get '[JSON] [Book] -- GET /books
        :<|> "books" :> ReqBody '[JSON] Book :> Post '[JSON] Book -- POST /books

myApi :: Proxy MyApi
myApi = Proxy

-- 'client' allows you to produce operations to query an API from a client.
postNewBook :: Book -> ClientM Book
getAllBooks :: ClientM [Book]
(getAllBooks :<|> postNewBook) = client myApi

-- the IOException happens already in withClientEnvIO
main' :: IO ()
main' = do
    let burl = BaseUrl Http "localhost" 8081 ""
    withClientEnvIO burl $ \env -> do
        res <- runClientM getAllBooks env
        case res of
            Left err -> putStrLn $ "Error: " ++ show err
            Right books -> print books

main :: IO ()
main = return ()

Changes

The latest version of this document is on GitHub. Changelog for servant package contains significant entries for all core packages.

0.20.2

Compatibility with newer dependencies and GHC versions

0.20

Compatibility with GHC series 9.2, 9.4, 9.6

0.18.4

Significant changes

servant-client / servant-client-core / servant-http-streams: Fix erroneous behavior, where only 2XX status codes would be considered successful, irrelevant of the status parameter specified by the verb combinator. (#1469)

0.18.3

Other changes

Support GHC-9.0.1.
Fix test suite running in CI.
Bump bytestring and hspec dependencies.

0.18.2

Significant changes

Support servant-client-core 0.18.2.

0.18.1

Significant changes

Union verbs

Other changes

Bump “tested-with” ghc versions

0.18

Significant changes

Support for ghc8.8 (#1318, #1326, #1327)

0.17

Significant changes

Add NoContentVerb #1028 #1219 #1228

The NoContent API endpoints should now use NoContentVerb combinator. The API type changes are usually of the kind
```
- :<|> PostNoContent '[JSON] NoContent
+ :<|> PostNoContent
```
i.e. one doesn’t need to specify the content-type anymore. There is no content.
Capture can be Lenient #1155 #1156

You can specify a lenient capture as
```
:<|> "capture-lenient"  :> Capture' '[Lenient] "foo" Int :> GET
```
which will make the capture always succeed. Handlers will be of the type Either String CapturedType, where Left err represents the possible parse failure.

Other changes

servant-client servant-client-core servant-http-streams Fix Verb with headers checking content type differently #1200 #1204

For Verbs with response Headers, the implementation didn’t check for the content-type of the response. Now it does.
servant-client servant-http-streams HasClient instance for Stream with Headers #1170 #1197
servant-client Redact the authorization header in Show and exceptions #1238

0.16.0.1

Allow base-compat-0.11

0.16

Initial release