servant-server-0.19.2: A family of combinators for defining webservices APIs and serving them
Safe Haskell None
Language Haskell2010

Servant.Server

Description

This module lets you implement Server s for defined APIs. You'll most likely just need serve .

Synopsis

Run a wai application from an API

serve :: HasServer api '[] => Proxy api -> Server api -> Application Source #

serve allows you to implement an API and produce a wai Application .

Example:

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

server :: Server MyApi
server = listAllBooks :<|> postBook
  where listAllBooks = ...
        postBook book = ...

myApi :: Proxy MyApi
myApi = Proxy

app :: Application
app = serve myApi server

main :: IO ()
main = Network.Wai.Handler.Warp.run 8080 app

serveWithContext :: ( HasServer api context, ServerContext context) => Proxy api -> Context context -> Server api -> Application Source #

Like serve , but allows you to pass custom context.

defaultErrorFormatters will always be appended to the end of the passed context, but if you pass your own formatter, it will override the default one.

serveWithContextT :: forall api context m. ( HasServer api context, ServerContext context) => Proxy api -> Context context -> ( forall x. m x -> Handler x) -> ServerT api m -> Application Source #

A general serve function that allows you to pass a custom context and hoisting function to apply on all routes.

type ServerContext context = HasContextEntry (context .++ DefaultErrorFormatters ) ErrorFormatters Source #

Constraints that need to be satisfied on a context for it to be passed to serveWithContext .

Typically, this will add default context entries to the context. You shouldn't typically need to worry about these constraints, but if you write a helper function that wraps serveWithContext , you might need to include this constraint.

Construct a wai Application from an API

Handlers for all standard combinators

class HasServer api context where Source #

Associated Types

type ServerT api (m :: * -> *) :: * Source #

Methods

route :: Proxy api -> Context context -> Delayed env ( Server api) -> Router env Source #

hoistServerWithContext :: Proxy api -> Proxy context -> ( forall x. m x -> n x) -> ServerT api m -> ServerT api n Source #

Instances

Instances details
( TypeError ( NoInstanceFor ( HasServer api context)) :: Constraint ) => HasServer (api :: k) context Source #
Instance details

Defined in Servant.Server.Internal

Associated Types

type ServerT api m Source #

Methods

route :: Proxy api -> Context context -> Delayed env ( Server api) -> Router env Source #

hoistServerWithContext :: Proxy api -> Proxy context -> ( forall x. m x -> n x) -> ServerT api m -> ServerT api n Source #

HasServer Raw context Source #

Just pass the request to the underlying application and serve its response.

Example:

type MyApi = "images" :> Raw

server :: Server MyApi
server = serveDirectory "/var/www/images"
Instance details

Defined in Servant.Server.Internal

Associated Types

type ServerT Raw m Source #

HasServer EmptyAPI context Source #

The server for an EmptyAPI is emptyServer .

type MyApi = "nothing" :> EmptyApi

server :: Server MyApi
server = emptyServer
Instance details

Defined in Servant.Server.Internal

Associated Types

type ServerT EmptyAPI m Source #

( HasServer ( ToServantApi api) context, forall (m :: Type -> Type ). Generic (api ( AsServerT m)), forall (m :: Type -> Type ). GServer api m) => HasServer ( NamedRoutes api :: Type ) context Source #
Instance details

Defined in Servant.Server.Internal

Associated Types

type ServerT ( NamedRoutes api) m Source #

( TypeError ( HasServerArrowTypeError a b) :: Constraint ) => HasServer (a -> b :: Type ) context Source #

This instance prevents from accidentally using -> instead of :>

>>> serve (Proxy :: Proxy (Capture "foo" Int -> Get '[JSON] Int)) (error "...")
...
...No instance HasServer (a -> b).
...Maybe you have used '->' instead of ':>' between
...Capture' '[] "foo" Int
...and
...Verb 'GET 200 '[JSON] Int
...
>>> undefined :: Server (Capture "foo" Int -> Get '[JSON] Int)
...
...No instance HasServer (a -> b).
...Maybe you have used '->' instead of ':>' between
...Capture' '[] "foo" Int
...and
...Verb 'GET 200 '[JSON] Int
...
Instance details

Defined in Servant.Server.Internal

Associated Types

type ServerT (a -> b) m Source #

Methods

route :: Proxy (a -> b) -> Context context -> Delayed env ( Server (a -> b)) -> Router env Source #

hoistServerWithContext :: Proxy (a -> b) -> Proxy context -> ( forall x. m x -> n x) -> ServerT (a -> b) m -> ServerT (a -> b) n Source #

ReflectMethod method => HasServer ( NoContentVerb method :: Type ) context Source #
Instance details

Defined in Servant.Server.Internal

Associated Types

type ServerT ( NoContentVerb method) m Source #

( HasServer a context, HasServer b context) => HasServer (a :<|> b :: Type ) context Source #

A server for a :<|> b first tries to match the request against the route represented by a and if it fails tries b . You must provide a request handler for each route.

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

server :: Server MyApi
server = listAllBooks :<|> postBook
  where listAllBooks = ...
        postBook book = ...
Instance details

Defined in Servant.Server.Internal

Associated Types

type ServerT (a :<|> b) m Source #

( HasContextEntry context ( NamedContext name subContext), HasServer subApi subContext) => HasServer ( WithNamedContext name subContext subApi :: Type ) context Source #
Instance details

Defined in Servant.Server.Internal

Associated Types

type ServerT ( WithNamedContext name subContext subApi) m Source #

Methods

route :: Proxy ( WithNamedContext name subContext subApi) -> Context context -> Delayed env ( Server ( WithNamedContext name subContext subApi)) -> Router env Source #

hoistServerWithContext :: Proxy ( WithNamedContext name subContext subApi) -> Proxy context -> ( forall x. m x -> n x) -> ServerT ( WithNamedContext name subContext subApi) m -> ServerT ( WithNamedContext name subContext subApi) n Source #

( ReflectMethod method, AllMime contentTypes, All (IsServerResourceWithStatus contentTypes) as, Unique ( Statuses as)) => HasServer ( UVerb method contentTypes as :: Type ) context Source #
Instance details

Defined in Servant.Server.UVerb

Associated Types

type ServerT ( UVerb method contentTypes as) m Source #

Methods

route :: Proxy ( UVerb method contentTypes as) -> Context context -> Delayed env ( Server ( UVerb method contentTypes as)) -> Router env Source #

hoistServerWithContext :: Proxy ( UVerb method contentTypes as) -> Proxy context -> ( forall x. m x -> n x) -> ServerT ( UVerb method contentTypes as) m -> ServerT ( UVerb method contentTypes as) n Source #

( TypeError ( PartialApplication ( HasServer :: k -> [ Type ] -> Constraint ) arr) :: Constraint ) => HasServer (arr :> sub :: Type ) context Source #
Instance details

Defined in Servant.Server.Internal

Associated Types

type ServerT (arr :> sub) m Source #

Methods

route :: Proxy (arr :> sub) -> Context context -> Delayed env ( Server (arr :> sub)) -> Router env Source #

hoistServerWithContext :: Proxy (arr :> sub) -> Proxy context -> ( forall x. m x -> n x) -> ServerT (arr :> sub) m -> ServerT (arr :> sub) n Source #

HasServer api context => HasServer ( HttpVersion :> api :: Type ) context Source #
Instance details

Defined in Servant.Server.Internal

Associated Types

type ServerT ( HttpVersion :> api) m Source #

( FramingUnrender framing, FromSourceIO chunk a, MimeUnrender ctype chunk, HasServer api context) => HasServer ( StreamBody' mods framing ctype a :> api :: Type ) context Source #
Instance details

Defined in Servant.Server.Internal

Associated Types

type ServerT ( StreamBody' mods framing ctype a :> api) m Source #

Methods

route :: Proxy ( StreamBody' mods framing ctype a :> api) -> Context context -> Delayed env ( Server ( StreamBody' mods framing ctype a :> api)) -> Router env Source #

hoistServerWithContext :: Proxy ( StreamBody' mods framing ctype a :> api) -> Proxy context -> ( forall x. m x -> n x) -> ServerT ( StreamBody' mods framing ctype a :> api) m -> ServerT ( StreamBody' mods framing ctype a :> api) n Source #

( AllCTUnrender list a, HasServer api context, SBoolI ( FoldLenient mods), HasContextEntry ( MkContextWithErrorFormatter context) ErrorFormatters ) => HasServer ( ReqBody' mods list a :> api :: Type ) context Source #

If you use ReqBody in one of the endpoints for your API, this automatically requires your server-side handler to be a function that takes an argument of the type specified by ReqBody . The Content-Type header is inspected, and the list provided is used to attempt deserialization. If the request does not have a Content-Type header, it is treated as application/octet-stream (as specified in RFC 7231 section 3.1.1.5 ). This lets servant worry about extracting it from the request and turning it into a value of the type you specify.

All it asks is for a FromJSON instance.

Example:

type MyApi = "books" :> ReqBody '[JSON] Book :> Post '[JSON] Book

server :: Server MyApi
server = postBook
  where postBook :: Book -> Handler Book
        postBook book = ...insert into your db...
Instance details

Defined in Servant.Server.Internal

Associated Types

type ServerT ( ReqBody' mods list a :> api) m Source #

Methods

route :: Proxy ( ReqBody' mods list a :> api) -> Context context -> Delayed env ( Server ( ReqBody' mods list a :> api)) -> Router env Source #

hoistServerWithContext :: Proxy ( ReqBody' mods list a :> api) -> Proxy context -> ( forall x. m x -> n x) -> ServerT ( ReqBody' mods list a :> api) m -> ServerT ( ReqBody' mods list a :> api) n Source #

HasServer api context => HasServer ( RemoteHost :> api :: Type ) context Source #
Instance details

Defined in Servant.Server.Internal

Associated Types

type ServerT ( RemoteHost :> api) m Source #

( KnownSymbol sym, FromHttpApiData a, HasServer api context, SBoolI ( FoldRequired mods), SBoolI ( FoldLenient mods), HasContextEntry ( MkContextWithErrorFormatter context) ErrorFormatters ) => HasServer ( QueryParam' mods sym a :> api :: Type ) context Source #

If you use QueryParam "author" Text in one of the endpoints for your API, this automatically requires your server-side handler to be a function that takes an argument of type Maybe Text .

This lets servant worry about looking it up in the query string and turning it into a value of the type you specify, enclosed in Maybe , because it may not be there and servant would then hand you Nothing .

You can control how it'll be converted from Text to your type by simply providing an instance of FromHttpApiData for your type.

Example:

type MyApi = "books" :> QueryParam "author" Text :> Get '[JSON] [Book]

server :: Server MyApi
server = getBooksBy
  where getBooksBy :: Maybe Text -> Handler [Book]
        getBooksBy Nothing       = ...return all books...
        getBooksBy (Just author) = ...return books by the given author...
Instance details

Defined in Servant.Server.Internal

Associated Types

type ServerT ( QueryParam' mods sym a :> api) m Source #

Methods

route :: Proxy ( QueryParam' mods sym a :> api) -> Context context -> Delayed env ( Server ( QueryParam' mods sym a :> api)) -> Router env Source #

hoistServerWithContext :: Proxy ( QueryParam' mods sym a :> api) -> Proxy context -> ( forall x. m x -> n x) -> ServerT ( QueryParam' mods sym a :> api) m -> ServerT ( QueryParam' mods sym a :> api) n Source #

( KnownSymbol sym, FromHttpApiData a, HasServer api context, HasContextEntry ( MkContextWithErrorFormatter context) ErrorFormatters ) => HasServer ( QueryParams sym a :> api :: Type ) context Source #

If you use QueryParams "authors" Text in one of the endpoints for your API, this automatically requires your server-side handler to be a function that takes an argument of type [ Text ] .

This lets servant worry about looking up 0 or more values in the query string associated to authors and turning each of them into a value of the type you specify.

You can control how the individual values are converted from Text to your type by simply providing an instance of FromHttpApiData for your type.

Example:

type MyApi = "books" :> QueryParams "authors" Text :> Get '[JSON] [Book]

server :: Server MyApi
server = getBooksBy
  where getBooksBy :: [Text] -> Handler [Book]
        getBooksBy authors = ...return all books by these authors...
Instance details

Defined in Servant.Server.Internal

Associated Types

type ServerT ( QueryParams sym a :> api) m Source #

( KnownSymbol sym, HasServer api context) => HasServer ( QueryFlag sym :> api :: Type ) context Source #

If you use QueryFlag "published" in one of the endpoints for your API, this automatically requires your server-side handler to be a function that takes an argument of type Bool .

Example:

type MyApi = "books" :> QueryFlag "published" :> Get '[JSON] [Book]

server :: Server MyApi
server = getBooks
  where getBooks :: Bool -> Handler [Book]
        getBooks onlyPublished = ...return all books, or only the ones that are already published, depending on the argument...
Instance details

Defined in Servant.Server.Internal

Associated Types

type ServerT ( QueryFlag sym :> api) m Source #

( KnownSymbol sym, FromHttpApiData a, HasServer api context, SBoolI ( FoldRequired mods), SBoolI ( FoldLenient mods), HasContextEntry ( MkContextWithErrorFormatter context) ErrorFormatters ) => HasServer ( Header' mods sym a :> api :: Type ) context Source #

If you use Header in one of the endpoints for your API, this automatically requires your server-side handler to be a function that takes an argument of the type specified by Header . This lets servant worry about extracting it from the request and turning it into a value of the type you specify.

All it asks is for a FromHttpApiData instance.

Example:

newtype Referer = Referer Text
  deriving (Eq, Show, FromHttpApiData)

           -- GET /view-my-referer
type MyApi = "view-my-referer" :> Header "Referer" Referer :> Get '[JSON] Referer

server :: Server MyApi
server = viewReferer
  where viewReferer :: Referer -> Handler referer
        viewReferer referer = return referer
Instance details

Defined in Servant.Server.Internal

Associated Types

type ServerT ( Header' mods sym a :> api) m Source #

Methods

route :: Proxy ( Header' mods sym a :> api) -> Context context -> Delayed env ( Server ( Header' mods sym a :> api)) -> Router env Source #

hoistServerWithContext :: Proxy ( Header' mods sym a :> api) -> Proxy context -> ( forall x. m x -> n x) -> ServerT ( Header' mods sym a :> api) m -> ServerT ( Header' mods sym a :> api) n Source #

HasServer api context => HasServer ( IsSecure :> api :: Type ) context Source #
Instance details

Defined in Servant.Server.Internal

Associated Types

type ServerT ( IsSecure :> api) m Source #

( AtLeastOneFragment api, FragmentUnique ( Fragment a1 :> api), HasServer api context) => HasServer ( Fragment a1 :> api :: Type ) context Source #

Ignore Fragment in server handlers. See https://ietf.org/rfc/rfc2616.html#section-15.1.3 for more details.

Example:

type MyApi = "books" :> Fragment Text :> Get '[JSON] [Book]

server :: Server MyApi
server = getBooks
  where getBooks :: Handler [Book]
        getBooks = ...return all books...
Instance details

Defined in Servant.Server.Internal

Associated Types

type ServerT ( Fragment a1 :> api) m Source #

( HasServer api context, HasContextEntry context ( AuthHandler Request ( AuthServerData ( AuthProtect tag)))) => HasServer ( AuthProtect tag :> api :: Type ) context Source #

Known orphan instance.

Instance details

Defined in Servant.Server.Experimental.Auth

Associated Types

type ServerT ( AuthProtect tag :> api) m Source #

HasServer api ctx => HasServer ( Summary desc :> api :: Type ) ctx Source #

Ignore Summary in server handlers.

Instance details

Defined in Servant.Server.Internal

Associated Types

type ServerT ( Summary desc :> api) m Source #

HasServer api ctx => HasServer ( Description desc :> api :: Type ) ctx Source #

Ignore Description in server handlers.

Instance details

Defined in Servant.Server.Internal

Associated Types

type ServerT ( Description desc :> api) m Source #

( KnownSymbol capture, FromHttpApiData a, Typeable a, HasServer api context, SBoolI ( FoldLenient mods), HasContextEntry ( MkContextWithErrorFormatter context) ErrorFormatters ) => HasServer ( Capture' mods capture a :> api :: Type ) context Source #

If you use Capture in one of the endpoints for your API, this automatically requires your server-side handler to be a function that takes an argument of the type specified by the Capture . This lets servant worry about getting it from the URL and turning it into a value of the type you specify.

You can control how it'll be converted from Text to your type by simply providing an instance of FromHttpApiData for your type.

Example:

type MyApi = "books" :> Capture "isbn" Text :> Get '[JSON] Book

server :: Server MyApi
server = getBook
  where getBook :: Text -> Handler Book
        getBook isbn = ...
Instance details

Defined in Servant.Server.Internal

Associated Types

type ServerT ( Capture' mods capture a :> api) m Source #

Methods

route :: Proxy ( Capture' mods capture a :> api) -> Context context -> Delayed env ( Server ( Capture' mods capture a :> api)) -> Router env Source #

hoistServerWithContext :: Proxy ( Capture' mods capture a :> api) -> Proxy context -> ( forall x. m x -> n x) -> ServerT ( Capture' mods capture a :> api) m -> ServerT ( Capture' mods capture a :> api) n Source #

( KnownSymbol capture, FromHttpApiData a, Typeable a, HasServer api context, HasContextEntry ( MkContextWithErrorFormatter context) ErrorFormatters ) => HasServer ( CaptureAll capture a :> api :: Type ) context Source #

If you use CaptureAll in one of the endpoints for your API, this automatically requires your server-side handler to be a function that takes an argument of a list of the type specified by the CaptureAll . This lets servant worry about getting values from the URL and turning them into values of the type you specify.

You can control how they'll be converted from Text to your type by simply providing an instance of FromHttpApiData for your type.

Example:

type MyApi = "src" :> CaptureAll "segments" Text :> Get '[JSON] SourceFile

server :: Server MyApi
server = getSourceFile
  where getSourceFile :: [Text] -> Handler Book
        getSourceFile pathSegments = ...
Instance details

Defined in Servant.Server.Internal

Associated Types

type ServerT ( CaptureAll capture a :> api) m Source #

Methods

route :: Proxy ( CaptureAll capture a :> api) -> Context context -> Delayed env ( Server ( CaptureAll capture a :> api)) -> Router env Source #

hoistServerWithContext :: Proxy ( CaptureAll capture a :> api) -> Proxy context -> ( forall x. m x -> n x) -> ServerT ( CaptureAll capture a :> api) m -> ServerT ( CaptureAll capture a :> api) n Source #

( KnownSymbol realm, HasServer api context, HasContextEntry context ( BasicAuthCheck usr)) => HasServer ( BasicAuth realm usr :> api :: Type ) context Source #

Basic Authentication

Instance details

Defined in Servant.Server.Internal

Associated Types

type ServerT ( BasicAuth realm usr :> api) m Source #

Methods

route :: Proxy ( BasicAuth realm usr :> api) -> Context context -> Delayed env ( Server ( BasicAuth realm usr :> api)) -> Router env Source #

hoistServerWithContext :: Proxy ( BasicAuth realm usr :> api) -> Proxy context -> ( forall x. m x -> n x) -> ServerT ( BasicAuth realm usr :> api) m -> ServerT ( BasicAuth realm usr :> api) n Source #

HasServer api context => HasServer ( Vault :> api :: Type ) context Source #
Instance details

Defined in Servant.Server.Internal

Associated Types

type ServerT ( Vault :> api) m Source #

( KnownSymbol path, HasServer api context) => HasServer (path :> api :: Type ) context Source #

Make sure the incoming request starts with "/path" , strip it and pass the rest of the request path to api .

Instance details

Defined in Servant.Server.Internal

Associated Types

type ServerT (path :> api) m Source #

Methods

route :: Proxy (path :> api) -> Context context -> Delayed env ( Server (path :> api)) -> Router env Source #

hoistServerWithContext :: Proxy (path :> api) -> Proxy context -> ( forall x. m x -> n x) -> ServerT (path :> api) m -> ServerT (path :> api) n Source #

( TypeError ( NoInstanceForSub ( HasServer :: k2 -> [ Type ] -> Constraint ) ty) :: Constraint ) => HasServer (ty :> sub :: Type ) context Source #
Instance details

Defined in Servant.Server.Internal

Associated Types

type ServerT (ty :> sub) m Source #

Methods

route :: Proxy (ty :> sub) -> Context context -> Delayed env ( Server (ty :> sub)) -> Router env Source #

hoistServerWithContext :: Proxy (ty :> sub) -> Proxy context -> ( forall x. m x -> n x) -> ServerT (ty :> sub) m -> ServerT (ty :> sub) n Source #

( AllCTRender ctypes a, ReflectMethod method, KnownNat status, GetHeaders ( Headers h a)) => HasServer ( Verb method status ctypes ( Headers h a) :: Type ) context Source #
Instance details

Defined in Servant.Server.Internal

Associated Types

type ServerT ( Verb method status ctypes ( Headers h a)) m Source #

Methods

route :: Proxy ( Verb method status ctypes ( Headers h a)) -> Context context -> Delayed env ( Server ( Verb method status ctypes ( Headers h a))) -> Router env Source #

hoistServerWithContext :: Proxy ( Verb method status ctypes ( Headers h a)) -> Proxy context -> ( forall x. m x -> n x) -> ServerT ( Verb method status ctypes ( Headers h a)) m -> ServerT ( Verb method status ctypes ( Headers h a)) n Source #

( AllCTRender ctypes a, ReflectMethod method, KnownNat status) => HasServer ( Verb method status ctypes a :: Type ) context Source #
Instance details

Defined in Servant.Server.Internal

Associated Types

type ServerT ( Verb method status ctypes a) m Source #

Methods

route :: Proxy ( Verb method status ctypes a) -> Context context -> Delayed env ( Server ( Verb method status ctypes a)) -> Router env Source #

hoistServerWithContext :: Proxy ( Verb method status ctypes a) -> Proxy context -> ( forall x. m x -> n x) -> ServerT ( Verb method status ctypes a) m -> ServerT ( Verb method status ctypes a) n Source #

( MimeRender ctype chunk, ReflectMethod method, KnownNat status, FramingRender framing, ToSourceIO chunk a, GetHeaders ( Headers h a)) => HasServer ( Stream method status framing ctype ( Headers h a) :: Type ) context Source #
Instance details

Defined in Servant.Server.Internal

Associated Types

type ServerT ( Stream method status framing ctype ( Headers h a)) m Source #

Methods

route :: Proxy ( Stream method status framing ctype ( Headers h a)) -> Context context -> Delayed env ( Server ( Stream method status framing ctype ( Headers h a))) -> Router env Source #

hoistServerWithContext :: Proxy ( Stream method status framing ctype ( Headers h a)) -> Proxy context -> ( forall x. m x -> n x) -> ServerT ( Stream method status framing ctype ( Headers h a)) m -> ServerT ( Stream method status framing ctype ( Headers h a)) n Source #

( MimeRender ctype chunk, ReflectMethod method, KnownNat status, FramingRender framing, ToSourceIO chunk a) => HasServer ( Stream method status framing ctype a :: Type ) context Source #
Instance details

Defined in Servant.Server.Internal

Associated Types

type ServerT ( Stream method status framing ctype a) m Source #

Methods

route :: Proxy ( Stream method status framing ctype a) -> Context context -> Delayed env ( Server ( Stream method status framing ctype a)) -> Router env Source #

hoistServerWithContext :: Proxy ( Stream method status framing ctype a) -> Proxy context -> ( forall x. m x -> n x) -> ServerT ( Stream method status framing ctype a) m -> ServerT ( Stream method status framing ctype a) n Source #

newtype Handler a Source #

Instances

Instances details
Monad Handler Source #
Instance details

Defined in Servant.Server.Internal.Handler

Functor Handler Source #
Instance details

Defined in Servant.Server.Internal.Handler

MonadFail Handler Source #
Instance details

Defined in Servant.Server.Internal.Handler

Applicative Handler Source #
Instance details

Defined in Servant.Server.Internal.Handler

MonadIO Handler Source #
Instance details

Defined in Servant.Server.Internal.Handler

MonadThrow Handler Source #
Instance details

Defined in Servant.Server.Internal.Handler

MonadCatch Handler Source #
Instance details

Defined in Servant.Server.Internal.Handler

MonadMask Handler Source #
Instance details

Defined in Servant.Server.Internal.Handler

MonadBase IO Handler Source #
Instance details

Defined in Servant.Server.Internal.Handler

MonadBaseControl IO Handler Source #
Instance details

Defined in Servant.Server.Internal.Handler

Associated Types

type StM Handler a Source #

MonadError ServerError Handler Source #
Instance details

Defined in Servant.Server.Internal.Handler

Generic ( Handler a) Source #
Instance details

Defined in Servant.Server.Internal.Handler

Associated Types

type Rep ( Handler a) :: Type -> Type Source #

type StM Handler a Source #
Instance details

Defined in Servant.Server.Internal.Handler

type Rep ( Handler a) Source #
Instance details

Defined in Servant.Server.Internal.Handler

type Rep ( Handler a) = D1 (' MetaData "Handler" "Servant.Server.Internal.Handler" "servant-server-0.19.2-G0Z4CBXVk6K3TywlQVHRKg" ' True ) ( C1 (' MetaCons "Handler" ' PrefixI ' True ) ( S1 (' MetaSel (' Just "runHandler'") ' NoSourceUnpackedness ' NoSourceStrictness ' DecidedLazy ) ( Rec0 ( ExceptT ServerError IO a))))

Debugging the server layout

layout :: HasServer api '[] => Proxy api -> Text Source #

The function layout produces a textual description of the internal router layout for debugging purposes. Note that the router layout is determined just by the API, not by the handlers.

Example:

For the following API

type API =
       "a" :> "d" :> Get '[JSON] NoContent
  :<|> "b" :> Capture "x" Int :> Get '[JSON] Bool
  :<|> "c" :> Put '[JSON] Bool
  :<|> "a" :> "e" :> Get '[JSON] Int
  :<|> "b" :> Capture "x" Int :> Put '[JSON] Bool
  :<|> Raw

we get the following output:

/
├─ a/
│  ├─ d/
│  │  └─•
│  └─ e/
│     └─•
├─ b/
│  └─ <x::Int>/
│     ├─•
│     ┆
│     └─•
├─ c/
│  └─•
┆
└─ <raw>

Explanation of symbols:

├
Normal lines reflect static branching via a table.
a/
Nodes reflect static path components.
─•
Leaves reflect endpoints.
<x::Int>/
This is a delayed capture of a single path component named x , of expected type Int .
<raw>
This is a part of the API we do not know anything about.
┆
Dashed lines suggest a dynamic choice between the part above and below. If there is a success for fatal failure in the first part, that one takes precedence. If both parts fail, the "better" error code will be returned.

layoutWithContext :: HasServer api context => Proxy api -> Context context -> Text Source #

Variant of layout that takes an additional Context .

Enter / hoisting server

hoistServer :: HasServer api '[] => Proxy api -> ( forall x. m x -> n x) -> ServerT api m -> ServerT api n Source #

Hoist server implementation.

Sometimes our cherished Handler monad isn't quite the type you'd like for your handlers. Maybe you want to thread some configuration in a Reader monad. Or have your types ensure that your handlers don't do any IO. Use hoistServer (a successor of now deprecated enter ).

With hoistServer , you can provide a function, to convert any number of endpoints from one type constructor to another. For example

Note: Server Raw can also be entered. It will be retagged.

>>> import Control.Monad.Reader
>>> type ReaderAPI = "ep1" :> Get '[JSON] Int :<|> "ep2" :> Get '[JSON] String :<|> Raw :<|> EmptyAPI
>>> let readerApi = Proxy :: Proxy ReaderAPI
>>> let readerServer = return 1797 :<|> ask :<|> Tagged (error "raw server") :<|> emptyServer :: ServerT ReaderAPI (Reader String)
>>> let nt x = return (runReader x "hi")
>>> let mainServer = hoistServer readerApi nt readerServer :: Server ReaderAPI

Functions based on mmorph

Context

data Context contextTypes where Source #

Context s are used to pass values to combinators. (They are not meant to be used to pass parameters to your handlers, i.e. they should not replace any custom ReaderT -monad-stack that you're using with hoistServer .) If you don't use combinators that require any context entries, you can just use serve as always.

If you are using combinators that require a non-empty Context you have to use serveWithContext and pass it a Context that contains all the values your combinators need. A Context is essentially a heterogeneous list and accessing the elements is being done by type (see getContextEntry ). The parameter of the type Context is a type-level list reflecting the types of the contained context entries. To create a Context with entries, use the operator ( :. ) :

>>> :type True :. () :. EmptyContext
True :. () :. EmptyContext :: Context '[Bool, ()]

Constructors

EmptyContext :: Context '[]
(:.) :: x -> Context xs -> Context (x ': xs) infixr 5

class HasContextEntry (context :: [*]) (val :: *) where Source #

This class is used to access context entries in Context s. getContextEntry returns the first value where the type matches:

>>> getContextEntry (True :. False :. EmptyContext) :: Bool
True

If the Context does not contain an entry of the requested type, you'll get an error:

>>> getContextEntry (True :. False :. EmptyContext) :: String
...
...No instance for (HasContextEntry '[] [Char])
...

Instances

Instances details
HasContextEntry (val ': xs) val Source #
Instance details

Defined in Servant.Server.Internal.Context

Methods

getContextEntry :: Context (val ': xs) -> val Source #

HasContextEntry xs val => HasContextEntry (notIt ': xs) val Source #
Instance details

Defined in Servant.Server.Internal.Context

Methods

getContextEntry :: Context (notIt ': xs) -> val Source #

type family (l1 :: [*]) .++ (l2 :: [*]) where ... Source #

Append two type-level lists.

Hint: import it as

import Servant.Server (type (.++))

Equations

'[] .++ a = a
(a ': as) .++ b = a ': (as .++ b)

(.++) :: Context l1 -> Context l2 -> Context (l1 .++ l2) Source #

Append two contexts.

NamedContext

data NamedContext (name :: Symbol ) (subContext :: [*]) Source #

Normally context entries are accessed by their types. In case you need to have multiple values of the same type in your Context and need to access them, we provide NamedContext . You can think of it as sub-namespaces for Context s.

Constructors

NamedContext ( Context subContext)

descendIntoNamedContext :: forall context name subContext. HasContextEntry context ( NamedContext name subContext) => Proxy (name :: Symbol ) -> Context context -> Context subContext Source #

descendIntoNamedContext allows you to access NamedContext s. Usually you won't have to use it yourself but instead use a combinator like WithNamedContext .

This is how descendIntoNamedContext works:

>>> :set -XFlexibleContexts
>>> let subContext = True :. EmptyContext
>>> :type subContext
subContext :: Context '[Bool]
>>> let parentContext = False :. (NamedContext subContext :: NamedContext "subContext" '[Bool]) :. EmptyContext
>>> :type parentContext
parentContext :: Context '[Bool, NamedContext "subContext" '[Bool]]
>>> descendIntoNamedContext (Proxy :: Proxy "subContext") parentContext :: Context '[Bool]
True :. EmptyContext

Basic Authentication

newtype BasicAuthCheck usr Source #

Datatype wrapping a function used to check authentication.

data BasicAuthResult usr Source #

servant-server's current implementation of basic authentication is not immune to certain kinds of timing attacks. Decoding payloads does not take a fixed amount of time.

The result of authentication/authorization

Instances

Instances details
Functor BasicAuthResult Source #
Instance details

Defined in Servant.Server.Internal.BasicAuth

Eq usr => Eq ( BasicAuthResult usr) Source #
Instance details

Defined in Servant.Server.Internal.BasicAuth

Read usr => Read ( BasicAuthResult usr) Source #
Instance details

Defined in Servant.Server.Internal.BasicAuth

Show usr => Show ( BasicAuthResult usr) Source #
Instance details

Defined in Servant.Server.Internal.BasicAuth

Generic ( BasicAuthResult usr) Source #
Instance details

Defined in Servant.Server.Internal.BasicAuth

Associated Types

type Rep ( BasicAuthResult usr) :: Type -> Type Source #

type Rep ( BasicAuthResult usr) Source #
Instance details

Defined in Servant.Server.Internal.BasicAuth

type Rep ( BasicAuthResult usr) = D1 (' MetaData "BasicAuthResult" "Servant.Server.Internal.BasicAuth" "servant-server-0.19.2-G0Z4CBXVk6K3TywlQVHRKg" ' False ) (( C1 (' MetaCons "Unauthorized" ' PrefixI ' False ) ( U1 :: Type -> Type ) :+: C1 (' MetaCons "BadPassword" ' PrefixI ' False ) ( U1 :: Type -> Type )) :+: ( C1 (' MetaCons "NoSuchUser" ' PrefixI ' False ) ( U1 :: Type -> Type ) :+: C1 (' MetaCons "Authorized" ' PrefixI ' False ) ( S1 (' MetaSel (' Nothing :: Maybe Symbol ) ' NoSourceUnpackedness ' NoSourceStrictness ' DecidedLazy ) ( Rec0 usr))))

General Authentication

Default error type

3XX

err300 :: ServerError Source #

err300 Multiple Choices

Example:

failingHandler :: Handler ()
failingHandler = throwError $ err300 { errBody = "I can't choose." }

err301 :: ServerError Source #

err301 Moved Permanently

Example:

failingHandler :: Handler ()
failingHandler = throwError err301

err302 :: ServerError Source #

err302 Found

Example:

failingHandler :: Handler ()
failingHandler = throwError err302

err303 :: ServerError Source #

err303 See Other

Example:

failingHandler :: Handler ()
failingHandler = throwError err303

err304 :: ServerError Source #

err304 Not Modified

Example:

failingHandler :: Handler ()
failingHandler = throwError err304

err305 :: ServerError Source #

err305 Use Proxy

Example:

failingHandler :: Handler ()
failingHandler = throwError err305

err307 :: ServerError Source #

err307 Temporary Redirect

Example:

failingHandler :: Handler ()
failingHandler = throwError err307

4XX

err400 :: ServerError Source #

err400 Bad Request

Example:

failingHandler :: Handler ()
failingHandler = throwError $ err400 { errBody = "Your request makes no sense to me." }

err401 :: ServerError Source #

err401 Unauthorized

Example:

failingHandler :: Handler ()
failingHandler = throwError $ err401 { errBody = "Your credentials are invalid." }

err402 :: ServerError Source #

err402 Payment Required

Example:

failingHandler :: Handler ()
failingHandler = throwError $ err402 { errBody = "You have 0 credits. Please give me $$$." }

err403 :: ServerError Source #

err403 Forbidden

Example:

failingHandler :: Handler ()
failingHandler = throwError $ err403 { errBody = "Please login first." }

err404 :: ServerError Source #

err404 Not Found

Example:

failingHandler :: Handler ()
failingHandler = throwError $ err404 { errBody = "Are you lost?" }

err405 :: ServerError Source #

err405 Method Not Allowed

Example:

failingHandler :: Handler ()
failingHandler = throwError $ err405 { errBody = "Your account privileges does not allow for this.  Please pay $$$." }

err406 :: ServerError Source #

err406 Not Acceptable

Example:

failingHandler :: Handler ()
failingHandler = throwError err406

err407 :: ServerError Source #

err407 Proxy Authentication Required

Example:

failingHandler :: Handler ()
failingHandler = throwError err407

err409 :: ServerError Source #

err409 Conflict

Example:

failingHandler :: Handler ()
failingHandler = throwError $ err409 { errBody = "Transaction conflicts with 59879cb56c7c159231eeacdd503d755f7e835f74" }

err410 :: ServerError Source #

err410 Gone

Example:

failingHandler :: Handler ()
failingHandler = throwError $ err410 { errBody = "I know it was here at some point, but.. I blame bad luck." }

err411 :: ServerError Source #

err411 Length Required

Example:

failingHandler :: Handler ()
failingHandler = throwError err411

err412 :: ServerError Source #

err412 Precondition Failed

Example:

failingHandler :: Handler ()
failingHandler = throwError $ err412 { errBody = "Precondition fail: x < 42 && y > 57" }

err413 :: ServerError Source #

err413 Request Entity Too Large

Example:

failingHandler :: Handler ()
failingHandler = throwError $ err413 { errBody = "Request exceeded 64k." }

err414 :: ServerError Source #

err414 Request-URI Too Large

Example:

failingHandler :: Handler ()
failingHandler = throwError $ err414 { errBody = "Maximum length is 64." }

err415 :: ServerError Source #

err415 Unsupported Media Type

Example:

failingHandler :: Handler ()
failingHandler = throwError $ err415 { errBody = "Supported media types:  gif, png" }

err416 :: ServerError Source #

err416 Request range not satisfiable

Example:

failingHandler :: Handler ()
failingHandler = throwError $ err416 { errBody = "Valid range is [0, 424242]." }

err417 :: ServerError Source #

err417 Expectation Failed

Example:

failingHandler :: Handler ()
failingHandler = throwError $ err417 { errBody = "I found a quux in the request.  This isn't going to work." }

err418 :: ServerError Source #

err418 Expectation Failed

Example:

failingHandler :: Handler ()
failingHandler = throwError $ err418 { errBody = "Apologies, this is not a webserver but a teapot." }

err422 :: ServerError Source #

err422 Unprocessable Entity

Example:

failingHandler :: Handler ()
failingHandler = throwError $ err422 { errBody = "I understood your request, but can't process it." }

5XX

err500 :: ServerError Source #

err500 Internal Server Error

Example:

failingHandler :: Handler ()
failingHandler = throwError $ err500 { errBody = "Exception in module A.B.C:55.  Have a great day!" }

err501 :: ServerError Source #

err501 Not Implemented

Example:

failingHandler :: Handler ()
failingHandler = throwError $ err501 { errBody = "/v1/foo is not supported with quux in the request." }

err502 :: ServerError Source #

err502 Bad Gateway

Example:

failingHandler :: Handler ()
failingHandler = throwError $ err502 { errBody = "Tried gateway foo, bar, and baz.  None responded." }

err503 :: ServerError Source #

err503 Service Unavailable

Example:

failingHandler :: Handler ()
failingHandler = throwError $ err503 { errBody = "We're rewriting in PHP." }

err504 :: ServerError Source #

err504 Gateway Time-out

Example:

failingHandler :: Handler ()
failingHandler = throwError $ err504 { errBody = "Backend foobar did not respond in 5 seconds." }

err505 :: ServerError Source #

err505 HTTP Version not supported

Example usage:

failingHandler :: Handler ()
failingHandler = throwError $ err505 { errBody = "I support HTTP/4.0 only." }

Formatting of errors from combinators

You can configure how Servant will render errors that occur while parsing the request.

type ErrorFormatter = TypeRep -> Request -> String -> ServerError Source #

A custom formatter for errors produced by parsing combinators like ReqBody or Capture .

A TypeRep argument described the concrete combinator that raised the error, allowing formatter to customize the message for different combinators.

A full Request is also passed so that the formatter can react to Accept header, for example.

type NotFoundErrorFormatter = Request -> ServerError Source #

This formatter does not get neither TypeRep nor error message.

data ErrorFormatters Source #

A collection of error formatters for different situations.

If you need to override one of them, use defaultErrorFormatters with record update syntax.

urlParseErrorFormatter :: ErrorFormatters -> ErrorFormatter Source #

Format error from parsing url parts or query parameters.

type DefaultErrorFormatters = '[ ErrorFormatters ] Source #

Context that contains default error formatters.

defaultErrorFormatters :: ErrorFormatters Source #

Default formatters will just return HTTP 400 status code with error message as response body.

Re-exports

type Application = Request -> ( Response -> IO ResponseReceived ) -> IO ResponseReceived Source #

The WAI application.

Note that, since WAI 3.0, this type is structured in continuation passing style to allow for proper safe resource handling. This was handled in the past via other means (e.g., ResourceT ). As a demonstration:

app :: Application
app req respond = bracket_
    (putStrLn "Allocating scarce resource")
    (putStrLn "Cleaning up")
    (respond $ responseLBS status200 [] "Hello World")

newtype Tagged (s :: k) b Source #

A Tagged s b value is a value b with an attached phantom type s . This can be used in place of the more traditional but less safe idiom of passing in an undefined value with the type, because unlike an (s -> b) , a Tagged s b can't try to use the argument s as a real value.

Moreover, you don't have to rely on the compiler to inline away the extra argument, because the newtype is "free"

Tagged has kind k -> * -> * if the compiler supports PolyKinds , therefore there is an extra k showing in the instance haddocks that may cause confusion.

Constructors

Tagged

Fields

Instances

Instances details
Bifunctor ( Tagged :: Type -> Type -> Type )
Instance details

Defined in Data.Tagged

Methods

bimap :: (a -> b) -> (c -> d) -> Tagged a c -> Tagged b d Source #

first :: (a -> b) -> Tagged a c -> Tagged b c Source #

second :: (b -> c) -> Tagged a b -> Tagged a c Source #

Bitraversable ( Tagged :: Type -> Type -> Type )
Instance details

Defined in Data.Tagged

Methods

bitraverse :: Applicative f => (a -> f c) -> (b -> f d) -> Tagged a b -> f ( Tagged c d) Source #

Bifoldable ( Tagged :: Type -> Type -> Type )
Instance details

Defined in Data.Tagged

Methods

bifold :: Monoid m => Tagged m m -> m Source #

bifoldMap :: Monoid m => (a -> m) -> (b -> m) -> Tagged a b -> m Source #

bifoldr :: (a -> c -> c) -> (b -> c -> c) -> c -> Tagged a b -> c Source #

bifoldl :: (c -> a -> c) -> (c -> b -> c) -> c -> Tagged a b -> c Source #

Eq2 ( Tagged :: Type -> Type -> Type )
Instance details

Defined in Data.Tagged

Methods

liftEq2 :: (a -> b -> Bool ) -> (c -> d -> Bool ) -> Tagged a c -> Tagged b d -> Bool Source #

Ord2 ( Tagged :: Type -> Type -> Type )
Instance details

Defined in Data.Tagged

Methods

liftCompare2 :: (a -> b -> Ordering ) -> (c -> d -> Ordering ) -> Tagged a c -> Tagged b d -> Ordering Source #

Read2 ( Tagged :: Type -> Type -> Type )
Instance details

Defined in Data.Tagged

Show2 ( Tagged :: Type -> Type -> Type )
Instance details

Defined in Data.Tagged

Methods

liftShowsPrec2 :: ( Int -> a -> ShowS ) -> ([a] -> ShowS ) -> ( Int -> b -> ShowS ) -> ([b] -> ShowS ) -> Int -> Tagged a b -> ShowS Source #

liftShowList2 :: ( Int -> a -> ShowS ) -> ([a] -> ShowS ) -> ( Int -> b -> ShowS ) -> ([b] -> ShowS ) -> [ Tagged a b] -> ShowS Source #

Generic1 ( Tagged s :: Type -> Type )
Instance details

Defined in Data.Tagged

Associated Types

type Rep1 ( Tagged s) :: k -> Type Source #

Methods

from1 :: forall (a :: k). Tagged s a -> Rep1 ( Tagged s) a Source #

to1 :: forall (a :: k). Rep1 ( Tagged s) a -> Tagged s a Source #

Monad ( Tagged s)
Instance details

Defined in Data.Tagged

Functor ( Tagged s)
Instance details

Defined in Data.Tagged

Methods

fmap :: (a -> b) -> Tagged s a -> Tagged s b Source #

(<$) :: a -> Tagged s b -> Tagged s a Source #

Applicative ( Tagged s)
Instance details

Defined in Data.Tagged

Foldable ( Tagged s)
Instance details

Defined in Data.Tagged

Traversable ( Tagged s)
Instance details

Defined in Data.Tagged

Eq1 ( Tagged s)
Instance details

Defined in Data.Tagged

Methods

liftEq :: (a -> b -> Bool ) -> Tagged s a -> Tagged s b -> Bool Source #

Ord1 ( Tagged s)
Instance details

Defined in Data.Tagged

Read1 ( Tagged s)
Instance details

Defined in Data.Tagged

Show1 ( Tagged s)
Instance details

Defined in Data.Tagged

Bounded b => Bounded ( Tagged s b)
Instance details

Defined in Data.Tagged

Enum a => Enum ( Tagged s a)
Instance details

Defined in Data.Tagged

Eq b => Eq ( Tagged s b)
Instance details

Defined in Data.Tagged

Floating a => Floating ( Tagged s a)
Instance details

Defined in Data.Tagged

Fractional a => Fractional ( Tagged s a)
Instance details

Defined in Data.Tagged

Integral a => Integral ( Tagged s a)
Instance details

Defined in Data.Tagged

( Data s, Data b) => Data ( Tagged s b)
Instance details

Defined in Data.Tagged

Methods

gfoldl :: ( forall d b0. Data d => c (d -> b0) -> d -> c b0) -> ( forall g. g -> c g) -> Tagged s b -> c ( Tagged s b) Source #

gunfold :: ( forall b0 r. Data b0 => c (b0 -> r) -> c r) -> ( forall r. r -> c r) -> Constr -> c ( Tagged s b) Source #

toConstr :: Tagged s b -> Constr Source #

dataTypeOf :: Tagged s b -> DataType Source #

dataCast1 :: Typeable t => ( forall d. Data d => c (t d)) -> Maybe (c ( Tagged s b)) Source #

dataCast2 :: Typeable t => ( forall d e. ( Data d, Data e) => c (t d e)) -> Maybe (c ( Tagged s b)) Source #

gmapT :: ( forall b0. Data b0 => b0 -> b0) -> Tagged s b -> Tagged s b Source #

gmapQl :: (r -> r' -> r) -> r -> ( forall d. Data d => d -> r') -> Tagged s b -> r Source #

gmapQr :: forall r r'. (r' -> r -> r) -> r -> ( forall d. Data d => d -> r') -> Tagged s b -> r Source #

gmapQ :: ( forall d. Data d => d -> u) -> Tagged s b -> [u] Source #

gmapQi :: Int -> ( forall d. Data d => d -> u) -> Tagged s b -> u Source #

gmapM :: Monad m => ( forall d. Data d => d -> m d) -> Tagged s b -> m ( Tagged s b) Source #

gmapMp :: MonadPlus m => ( forall d. Data d => d -> m d) -> Tagged s b -> m ( Tagged s b) Source #

gmapMo :: MonadPlus m => ( forall d. Data d => d -> m d) -> Tagged s b -> m ( Tagged s b) Source #

Num a => Num ( Tagged s a)
Instance details

Defined in Data.Tagged

Ord b => Ord ( Tagged s b)
Instance details

Defined in Data.Tagged

Read b => Read ( Tagged s b)
Instance details

Defined in Data.Tagged

Real a => Real ( Tagged s a)
Instance details

Defined in Data.Tagged

RealFloat a => RealFloat ( Tagged s a)
Instance details

Defined in Data.Tagged

RealFrac a => RealFrac ( Tagged s a)
Instance details

Defined in Data.Tagged

Show b => Show ( Tagged s b)
Instance details

Defined in Data.Tagged

Ix b => Ix ( Tagged s b)
Instance details

Defined in Data.Tagged

IsString a => IsString ( Tagged s a)
Instance details

Defined in Data.Tagged

Generic ( Tagged s b)
Instance details

Defined in Data.Tagged

Associated Types

type Rep ( Tagged s b) :: Type -> Type Source #

Semigroup a => Semigroup ( Tagged s a)
Instance details

Defined in Data.Tagged

( Semigroup a, Monoid a) => Monoid ( Tagged s a)
Instance details

Defined in Data.Tagged

Storable a => Storable ( Tagged s a)
Instance details

Defined in Data.Tagged

Bits a => Bits ( Tagged s a)
Instance details

Defined in Data.Tagged

FiniteBits a => FiniteBits ( Tagged s a)
Instance details

Defined in Data.Tagged

NFData b => NFData ( Tagged s b)
Instance details

Defined in Data.Tagged

Methods

rnf :: Tagged s b -> () Source #

ToFormKey a => ToFormKey ( Tagged b a)
Instance details

Defined in Web.Internal.FormUrlEncoded

FromFormKey a => FromFormKey ( Tagged b a)
Instance details

Defined in Web.Internal.FormUrlEncoded

ToHttpApiData a => ToHttpApiData ( Tagged b a)

Note: this instance is not polykinded

Instance details

Defined in Web.Internal.HttpApiData

FromHttpApiData a => FromHttpApiData ( Tagged b a)

Note: this instance is not polykinded

Instance details

Defined in Web.Internal.HttpApiData

type Rep1 ( Tagged s :: Type -> Type )
Instance details

Defined in Data.Tagged

type Rep1 ( Tagged s :: Type -> Type ) = D1 (' MetaData "Tagged" "Data.Tagged" "tagged-0.8.7-Hh8SrsJ8Ofo2TZerdJ0cCc" ' True ) ( C1 (' MetaCons "Tagged" ' PrefixI ' True ) ( S1 (' MetaSel (' Just "unTagged") ' NoSourceUnpackedness ' NoSourceStrictness ' DecidedLazy ) Par1 ))
type Rep ( Tagged s b)
Instance details

Defined in Data.Tagged

type Rep ( Tagged s b) = D1 (' MetaData "Tagged" "Data.Tagged" "tagged-0.8.7-Hh8SrsJ8Ofo2TZerdJ0cCc" ' True ) ( C1 (' MetaCons "Tagged" ' PrefixI ' True ) ( S1 (' MetaSel (' Just "unTagged") ' NoSourceUnpackedness ' NoSourceStrictness ' DecidedLazy ) ( Rec0 b)))