| Safe Haskell | None |
|---|---|
| Language | Haskell2010 |
Servant.Server
Contents
Description
- serve :: HasServer api '[] => Proxy api -> Server api -> Application
- serveWithContext :: HasServer api context => Proxy api -> Context context -> Server api -> Application
- toApplication :: RoutingApplication -> Application
- class HasServer api context where
- type Server api = ServerT api Handler
- data EmptyServer
- emptyServer :: ServerT EmptyAPI m
- newtype Handler a = Handler {
- runHandler' :: ExceptT ServantErr IO a
- runHandler :: Handler a -> IO (Either ServantErr a)
- layout :: HasServer api '[] => Proxy api -> Text
- layoutWithContext :: HasServer api context => Proxy api -> Context context -> Text
- hoistServer :: HasServer api '[] => Proxy api -> (forall x. m x -> n x) -> ServerT api m -> ServerT api n
- tweakResponse :: (RouteResult Response -> RouteResult Response) -> Router env -> Router env
- data Context contextTypes where
- EmptyContext :: Context '[]
- (:.) :: x -> Context xs -> Context (x ': xs)
- class HasContextEntry (context :: [*]) (val :: *) where
- data NamedContext (name :: Symbol) (subContext :: [*]) = NamedContext (Context subContext)
- descendIntoNamedContext :: forall context name subContext. HasContextEntry context (NamedContext name subContext) => Proxy (name :: Symbol) -> Context context -> Context subContext
- newtype BasicAuthCheck usr = BasicAuthCheck {
- unBasicAuthCheck :: BasicAuthData -> IO (BasicAuthResult usr)
- data BasicAuthResult usr
- = Unauthorized
- | BadPassword
- | NoSuchUser
- | Authorized usr
- data ServantErr = ServantErr {
- errHTTPCode :: Int
- errReasonPhrase :: String
- errBody :: ByteString
- errHeaders :: [Header]
- err300 :: ServantErr
- err301 :: ServantErr
- err302 :: ServantErr
- err303 :: ServantErr
- err304 :: ServantErr
- err305 :: ServantErr
- err307 :: ServantErr
- err400 :: ServantErr
- err401 :: ServantErr
- err402 :: ServantErr
- err403 :: ServantErr
- err404 :: ServantErr
- err405 :: ServantErr
- err406 :: ServantErr
- err407 :: ServantErr
- err409 :: ServantErr
- err410 :: ServantErr
- err411 :: ServantErr
- err412 :: ServantErr
- err413 :: ServantErr
- err414 :: ServantErr
- err415 :: ServantErr
- err416 :: ServantErr
- err417 :: ServantErr
- err418 :: ServantErr
- err422 :: ServantErr
- err500 :: ServantErr
- err501 :: ServantErr
- err502 :: ServantErr
- err503 :: ServantErr
- err504 :: ServantErr
- err505 :: ServantErr
- type Application = Request -> (Response -> IO ResponseReceived) -> IO ResponseReceived
- newtype Tagged k (s :: k) b :: forall k. k -> * -> * = Tagged {
- unTagged :: b
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 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 appserveWithContext :: HasServer api context => Proxy api -> Context context -> Server api -> Application Source #
Construct a wai Application from an API
Handlers for all standard combinators
class HasServer api context where Source #
Minimal complete definition
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
| 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" |
| HasServer * EmptyAPI context Source # | The server for an type MyApi = "nothing" :> EmptyApi server :: Server MyApi server = emptyAPIServer |
| TypeError Constraint (HasServerArrowTypeError * * a b) => HasServer * (a -> b) context Source # | This instance prevents from accidentally using '->' instead of
|
| (HasServer * a context, HasServer * b context) => HasServer * ((:<|>) a b) context Source # | A server for 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 = ... |
| (HasContextEntry context (NamedContext name subContext), HasServer * subApi subContext) => HasServer * (WithNamedContext name subContext subApi) context Source # | |
| TypeError Constraint (HasServerArrowKindError (k -> l) arr) => HasServer * ((:>) (k -> l) arr api) context Source # | This instance catches mistakes when there are non-saturated
type applications on LHS of
|
| HasServer * api context => HasServer * ((:>) * HttpVersion api) context Source # | |
| (AllCTUnrender list a, HasServer * api context, SBoolI (FoldLenient mods)) => HasServer * ((:>) * (ReqBody' mods list a) api) context Source # | If you use All it asks is for a 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... |
| HasServer * api context => HasServer * ((:>) * RemoteHost api) context Source # | |
| (KnownSymbol sym, FromHttpApiData a, HasServer * api context, SBoolI (FoldRequired mods), SBoolI (FoldLenient mods)) => HasServer * ((:>) * (QueryParam' mods sym a) api) context Source # | If you use 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 You can control how it'll be converted from 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... |
| (KnownSymbol sym, FromHttpApiData a, HasServer * api context) => HasServer * ((:>) * (QueryParams sym a) api) context Source # | If you use This lets servant worry about looking up 0 or more values in the query string
associated to You can control how the individual values are converted from 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... |
| (KnownSymbol sym, HasServer * api context) => HasServer * ((:>) * (QueryFlag sym) api) context Source # | If you use 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... |
| (KnownSymbol sym, FromHttpApiData a, HasServer * api context, SBoolI (FoldRequired mods), SBoolI (FoldLenient mods)) => HasServer * ((:>) * (Header' * mods sym a) api) context Source # | If you use All it asks is for a 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 |
| HasServer * api context => HasServer * ((:>) * IsSecure api) context Source # | |
| HasServer * api ctx => HasServer * ((:>) * (Summary desc) api) ctx Source # | Ignore |
| HasServer * api ctx => HasServer * ((:>) * (Description desc) api) ctx Source # | Ignore |
| (KnownSymbol capture, FromHttpApiData a, HasServer * api context) => HasServer * ((:>) * (Capture' mods capture a) api) context Source # | If you use You can control how it'll be converted from Example: type MyApi = "books" :> Capture "isbn" Text :> Get '[JSON] Book
server :: Server MyApi
server = getBook
where getBook :: Text -> Handler Book
getBook isbn = ... |
| (KnownSymbol capture, FromHttpApiData a, HasServer * api context) => HasServer * ((:>) * (CaptureAll capture a) api) context Source # | If you use You can control how they'll be converted from Example: type MyApi = "src" :> CaptureAll "segments" Text :> Get '[JSON] SourceFile
server :: Server MyApi
server = getSourceFile
where getSourceFile :: [Text] -> Handler Book
getSourceFile pathSegments = ... |
| (KnownSymbol realm, HasServer * api context, HasContextEntry context (BasicAuthCheck usr)) => HasServer * ((:>) * (BasicAuth realm usr) api) context Source # | Basic Authentication |
| HasServer * api context => HasServer * ((:>) * Vault api) context Source # | |
| (KnownSymbol path, HasServer * api context) => HasServer * ((:>) Symbol path api) context Source # | Make sure the incoming request starts with |
| (AllCTRender ctypes a, ReflectMethod k1 method, KnownNat status, GetHeaders (Headers h a)) => HasServer * (Verb k1 method status ctypes (Headers h a)) context Source # | |
| (AllCTRender ctypes a, ReflectMethod k1 method, KnownNat status) => HasServer * (Verb k1 method status ctypes a) context Source # | |
| (MimeRender * ctype a, ReflectMethod k1 method, FramingRender * * framing ctype, ToStreamGenerator f a, GetHeaders (Headers h (f a))) => HasServer * (Stream k1 method framing ctype (Headers h (f a))) context Source # | |
| (MimeRender * ctype a, ReflectMethod k1 method, FramingRender * * framing ctype, ToStreamGenerator f a) => HasServer * (Stream k1 method framing ctype (f a)) context Source # | |
Constructors
| Handler | |
Fields
| |
Instances
| Monad Handler Source # | |
| Functor Handler Source # | |
| Applicative Handler Source # | |
| MonadIO Handler Source # | |
| MonadThrow Handler Source # | |
| MonadCatch Handler Source # | |
| MonadBase IO Handler Source # | |
| MonadBaseControl IO Handler Source # | |
| MonadError ServantErr Handler Source # | |
| Generic (Handler a) Source # | |
| type StM Handler a Source # | |
| type Rep (Handler a) Source # | |
runHandler :: Handler a -> IO (Either ServantErr a) Source #
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
:<|> Rawwe get the following output:
/ ├─ a/ │ ├─ d/ │ │ └─• │ └─ e/ │ └─• ├─ b/ │ └─ <capture>/ │ ├─• │ ┆ │ └─• ├─ c/ │ └─• ┆ └─ <raw>
Explanation of symbols:
├- Normal lines reflect static branching via a table.
a/- Nodes reflect static path components.
─•- Leaves reflect endpoints.
<capture>/- This is a delayed capture of a path component.
<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.
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
tweakResponse :: (RouteResult Response -> RouteResult Response) -> Router env -> Router env Source #
Apply a transformation to the response of a Router.
Context
data Context contextTypes where Source #
Contexts 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 Enter.) 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 heterogenous
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 :. () :. EmptyContextTrue :. () :. 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 Contexts. getContextEntry
returns the first value where the type matches:
>>>getContextEntry (True :. False :. EmptyContext) :: BoolTrue
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]) ...
Minimal complete definition
Methods
getContextEntry :: Context context -> val Source #
Instances
| HasContextEntry ((:) * val xs) val Source # | |
| HasContextEntry xs val => HasContextEntry ((:) * notIt xs) val Source # | |
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
Contexts.
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 NamedContexts. 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 subContextsubContext :: Context '[Bool]>>>let parentContext = False :. (NamedContext subContext :: NamedContext "subContext" '[Bool]) :. EmptyContext>>>:type parentContextparentContext :: 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.
Constructors
| BasicAuthCheck | |
Fields
| |
Instances
| Functor BasicAuthCheck Source # | |
| Generic (BasicAuthCheck usr) Source # | |
| type Rep (BasicAuthCheck usr) Source # | |
data BasicAuthResult usr Source #
servant-server's current implementation of basic authentication is not immune to certian kinds of timing attacks. Decoding payloads does not take a fixed amount of time.
The result of authentication/authorization
Constructors
| Unauthorized | |
| BadPassword | |
| NoSuchUser | |
| Authorized usr |
Instances
| Functor BasicAuthResult Source # | |
| Eq usr => Eq (BasicAuthResult usr) Source # | |
| Read usr => Read (BasicAuthResult usr) Source # | |
| Show usr => Show (BasicAuthResult usr) Source # | |
| Generic (BasicAuthResult usr) Source # | |
| type Rep (BasicAuthResult usr) Source # | |
General Authentication
Default error type
data ServantErr Source #
Constructors
| ServantErr | |
Fields
| |
Instances
3XX
err300 :: ServantErr Source #
err300 Multiple Choices
Example:
failingHandler :: Handler ()
failingHandler = throwError $ err300 { errBody = "I can't choose." }err301 :: ServantErr Source #
err302 :: ServantErr Source #
err303 :: ServantErr Source #
err304 :: ServantErr Source #
err305 :: ServantErr Source #
err307 :: ServantErr Source #
4XX
err400 :: ServantErr Source #
err400 Bad Request
Example:
failingHandler :: Handler ()
failingHandler = throwError $ err400 { errBody = "Your request makes no sense to me." }err401 :: ServantErr Source #
err401 Unauthorized
Example:
failingHandler :: Handler ()
failingHandler = throwError $ err401 { errBody = "Your credentials are invalid." }err402 :: ServantErr Source #
err402 Payment Required
Example:
failingHandler :: Handler ()
failingHandler = throwError $ err402 { errBody = "You have 0 credits. Please give me $$$." }err403 :: ServantErr Source #
err403 Forbidden
Example:
failingHandler :: Handler ()
failingHandler = throwError $ err403 { errBody = "Please login first." }err404 :: ServantErr Source #
err404 Not Found
Example:
failingHandler :: Handler ()
failingHandler = throwError $ err404 { errBody = "(╯°□°）╯︵ ┻━┻)." }err405 :: ServantErr Source #
err405 Method Not Allowed
Example:
failingHandler :: Handler ()
failingHandler = throwError $ err405 { errBody = "Your account privileges does not allow for this. Please pay $$$." }err406 :: ServantErr Source #
err407 :: ServantErr Source #
err407 Proxy Authentication Required
Example:
failingHandler :: Handler () failingHandler = throwError err407
err409 :: ServantErr Source #
err409 Conflict
Example:
failingHandler :: Handler ()
failingHandler = throwError $ err409 { errBody = "Transaction conflicts with 59879cb56c7c159231eeacdd503d755f7e835f74" }err410 :: ServantErr Source #
err410 Gone
Example:
failingHandler :: Handler ()
failingHandler = throwError $ err410 { errBody = "I know it was here at some point, but.. I blame bad luck." }err411 :: ServantErr Source #
err412 :: ServantErr Source #
err412 Precondition Failed
Example:
failingHandler :: Handler ()
failingHandler = throwError $ err412 { errBody = "Precondition fail: x < 42 && y > 57" }err413 :: ServantErr Source #
err413 Request Entity Too Large
Example:
failingHandler :: Handler ()
failingHandler = throwError $ err413 { errBody = "Request exceeded 64k." }err414 :: ServantErr Source #
err414 Request-URI Too Large
Example:
failingHandler :: Handler ()
failingHandler = throwError $ err414 { errBody = "Maximum length is 64." }err415 :: ServantErr Source #
err415 Unsupported Media Type
Example:
failingHandler :: Handler ()
failingHandler = throwError $ err415 { errBody = "Supported media types: gif, png" }err416 :: ServantErr Source #
err416 Request range not satisfiable
Example:
failingHandler :: Handler ()
failingHandler = throwError $ err416 { errBody = "Valid range is [0, 424242]." }err417 :: ServantErr 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 :: ServantErr Source #
err418 Expectation Failed
Example:
failingHandler :: Handler ()
failingHandler = throwError $ err418 { errBody = "Apologies, this is not a webserver but a teapot." }err422 :: ServantErr Source #
err422 Unprocessable Entity
Example:
failingHandler :: Handler ()
failingHandler = throwError $ err422 { errBody = "I understood your request, but can't process it." }5XX
err500 :: ServantErr Source #
err500 Internal Server Error
Example:
failingHandler :: Handler ()
failingHandler = throwError $ err500 { errBody = "Exception in module A.B.C:55. Have a great day!" }err501 :: ServantErr Source #
err501 Not Implemented
Example:
failingHandler :: Handler ()
failingHandler = throwError $ err501 { errBody = "/v1/foo is not supported with quux in the request." }err502 :: ServantErr Source #
err502 Bad Gateway
Example:
failingHandler :: Handler ()
failingHandler = throwError $ err502 { errBody = "Tried gateway foo, bar, and baz. None responded." }err503 :: ServantErr Source #
err503 Service Unavailable
Example:
failingHandler :: Handler ()
failingHandler = throwError $ err503 { errBody = "We're rewriting in PHP." }err504 :: ServantErr Source #
err504 Gateway Time-out
Example:
failingHandler :: Handler ()
failingHandler = throwError $ err504 { errBody = "Backend foobar did not respond in 5 seconds." }err505 :: ServantErr Source #
err505 HTTP Version not supported
Example usage:
failingHandler :: Handler ()
failingHandler = throwError $ err505 { errBody = "I support HTTP/4.0 only." }Re-exports
type Application = Request -> (Response -> IO ResponseReceived) -> IO ResponseReceived #
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 k (s :: k) b :: forall k. k -> * -> * #
A Tagged s bb 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 bs 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.
Instances