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

Package versions follow the Package Versioning Policy: in A.B.C, bumps to either A or B represent major versions.

0.20.2

• Fix build of examples/greet.hs. Add “429 Too Many Requests” error. #1591

• Full query string helpers #1604 This involves a new instance HasServer (QueryString :> api) context.

• Add MkHandler pattern synonym #1732 #1733

  Add a bidirectional pattern synonym to construct Handler a values from IO (Either ServerError a) ones, and match in the other direction.

• Add instance HasServer (EmptyAPI :> api) context #1775

• Bugfix - CaptureAll produces [””] for empty paths due to trailing slash. #1243 #1516

  CaptureAll resulted in [""] for empty paths due to trailing slash. Similar oddities occurred around these edge cases like "/" resulted in [] correctly, but "//" resulted in ["", ""]. This patch simply eliminates the first "" in the pathinfo list as taken from the wai response. This might break user code that relies on personal shims to solve the problem, however simply removing their workarounds should fix their code as the behavior is now sane.

0.20

• Add API docs for ServerT #1573
• Add Functor instance to AuthHandler. #1638
• Compatibility with GHC 9.6. #1680

0.19.2

Compatibility with GHC 9.4, see PR #1592.

0.19.1

• Add MonadFail instance for Handler wrt #1545
• Support GHC 9.2 #1525
• Add capture hints in Router type for debug and display purposes [PR #1556] (http://github.com/haskell-servant/servant/pull/1556)

0.19

Significant changes

• Drop support for GHC < 8.6.
• Support GHC 9.0 (GHC 9.2 should work as well, but isn’t fully tested yet).
• Support Aeson 2 (#1475), which fixes a DOS vulnerability related to hash collisions.
• Add NamedRoutes combinator, making support for records first-class in Servant (#1388).
• Add custom type errors for partially applied combinators (#1289, #1486).

0.18.3

Significant changes

• Add response header support to UVerb (#1420)

Other changes

• Support GHC-9.0.1.
• Bump bytestring, hspec and base64-bytestring dependencies.

0.18.2

Significant changes

• Support Fragment combinator.

0.18.1

Significant changes

• Union verbs

Other changes

• Bump “tested-with” ghc versions
• Allow newer dependencies

0.18

Significant changes

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

• Configurable error messages for automatic errors thrown by servant, like “no route” or “could not parse json body” (#1312, #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.

• servant-server use queryString to parse QueryParam, QueryParams and QueryFlag #1249 #1262

  Some APIs need query parameters rewriting, e.g. in order to support for multiple casing (camel, snake, etc) or something to that effect.

  This could be easily achieved by using WAI Middleware and modifying request’s Query. But QueryParam, QueryParams and QueryFlag use rawQueryString. By using queryString rather then rawQueryString we can enable such rewritings.

• servant servant-server Make packages build-type: Simple #1263

  We used build-type: Custom, but it’s problematic e.g. for cross-compiling. The benefit is small, as the doctests can be run other ways too (though not so conveniently).

0.16.2

• singleton-bool-0.1.5 (SBool is re-exported)
  • Add discreteBool :: Dec (a :~: b) (GHC-7.8+)
  • Add Show, Eq, Ord SBool b instances.
• dependencies update

0.16.1

• Use http-api-data-0.4.1 (a part of its API is re-exported) #1181

0.16

• Rename ServantError to ClientError, ServantErr to ServerError #1131
• servant-server Reorder HTTP failure code priorities #1103
• servant-server Re-organise internal modules #1139
• Allow network-3.0 #1107

0.15

• Streaming refactoring. #991 #1076 #1077

  The streaming functionality (Servant.API.Stream) is refactored to use servant’s own SourceIO type (see Servant.Types.SourceT documentation), which replaces both StreamGenerator and ResultStream types.

  New conversion type-classes are ToSourceIO and FromSourceIO (replacing ToStreamGenerator and BuildFromStream). There are instances for conduit, pipes and machines in new packages: servant-conduit servant-pipes and servant-machines respectively.

  Writing new framing strategies is simpler. Check existing strategies for examples.

  This change shouldn’t affect you, if you don’t use streaming endpoints.

• Drop support for GHC older than 8.0 #1008 #1009

• servant NewlineFraming encodes newline after each element (i.e last) #1079 #1011

• servant Add lookupResponseHeader :: ... => Headers headers r -> ResponseHeader h a #1064

• servant-server Add MonadMask Handler #1068

• servant Export GetHeaders' #1052

• servant Add Bitraversable and other Bi- instances for :<|> #1032

• servant Add PutCreated method type alias #1024

• servant Add ToSourceIO (NonEmpty a) instance #988

0.14.1

• Merge in servant-generic (by Patrick Chilton) into servant (Servant.API.Generic), servant-client-code (Servant.Client.Generic) and servant-server (Servant.Server.Generic).

• servant-server Deprecate Servant.Utils.StaticUtils, use Servant.Server.StaticUtils.

0.14

• Stream takes a status code argument

  -Stream method        framing ctype a
  +Stream method status framing ctype a
  

  (#966 #972)

• ToStreamGenerator definition changed, so it’s possible to write an instance for conduits.

  -class ToStreamGenerator f a where
  -   toStreamGenerator :: f a -> StreamGenerator a
  +class ToStreamGenerator a b | a -> b where
  +   toStreamGenerator :: a -> StreamGenerator b
  

  (#959)

• Added NoFraming streaming strategy (#959)

• servant-server File serving in polymorphic monad. i.e. Generalised types of serveDirectoryFileServer etc functions in Servant.Utils.StaticFiles (#953)

• servant-server ReqBody content type check is recoverable. This allows writing APIs like:

        ReqBody '[JSON] Int      :> Post '[PlainText] Int
  :<|>  ReqBody '[PlainText] Int :> Post '[PlainText] Int
  

  which is useful when handlers are subtly different, for example may do less work. (