Merge pull request #959 from jvanbruegge/fix-stream

Change definition of StreamGenerator

Author: phadej

doc/tutorial/ApiType.lhs

@@ -137,7 +137,7 @@ type StreamGet  = Stream 'GET
 type StreamPost = Stream 'POST
 ```
 
-These describe endpoints that return a stream of values rather than just a single value. They not only take a single content type as a parameter, but also a framing strategy -- this specifies how the individual results are delineated from one another in the stream. The two standard strategies given with Servant are `NewlineFraming` and `NetstringFraming`, but others can be written to match other protocols.
+These describe endpoints that return a stream of values rather than just a single value. They not only take a single content type as a parameter, but also a framing strategy -- this specifies how the individual results are delineated from one another in the stream. The three standard strategies given with Servant are `NewlineFraming`, `NetstringFraming` and `NoFraming`, but others can be written to match other protocols.
 
 
 ### `Capture`

servant-client/test/Servant/StreamSpec.hs

@@ -40,7 +40,8 @@ import           Test.QuickCheck
 import           Servant.API         ((:<|>) ((:<|>)), (:>), JSON,
                                       NetstringFraming, NewlineFraming,
                                       OctetStream, ResultStream (..),
-                                      StreamGenerator (..), StreamGet)
+                                      StreamGenerator (..), StreamGet,
+                                      NoFraming)
 import           Servant.Client
 import           Servant.ClientSpec  (Person (..))
 import qualified Servant.ClientSpec  as CS
@@ -59,7 +60,7 @@ spec = describe "Servant.Stream" $ do
 type StreamApi f =
        "streamGetNewline" :> StreamGet NewlineFraming JSON (f Person)
   :<|> "streamGetNetstring" :> StreamGet  NetstringFraming JSON (f Person)
-  :<|> "streamALot" :> StreamGet NewlineFraming OctetStream (f BS.ByteString)
+  :<|> "streamALot" :> StreamGet NoFraming OctetStream (f BS.ByteString)
 
 
 capi :: Proxy (StreamApi ResultStream)

servant-server/src/Servant/Server/Internal.hs

@@ -284,34 +284,34 @@ instance OVERLAPPING_
 
 instance OVERLAPPABLE_
          ( MimeRender ctype a, ReflectMethod method,
-           FramingRender framing ctype, ToStreamGenerator f a
-         ) => HasServer (Stream method framing ctype (f a)) context where
+           FramingRender framing ctype, ToStreamGenerator b a
+         ) => HasServer (Stream method framing ctype b) context where
 
-  type ServerT (Stream method framing ctype (f a)) m = m (f a)
+  type ServerT (Stream method framing ctype b) m = m b
   hoistServerWithContext _ _ nt s = nt s
 
   route Proxy _ = streamRouter ([],) method (Proxy :: Proxy framing) (Proxy :: Proxy ctype)
       where method = reflectMethod (Proxy :: Proxy method)
 
 instance OVERLAPPING_
          ( MimeRender ctype a, ReflectMethod method,
-           FramingRender framing ctype, ToStreamGenerator f a,
-           GetHeaders (Headers h (f a))
-         ) => HasServer (Stream method framing ctype (Headers h (f a))) context where
+           FramingRender framing ctype, ToStreamGenerator b a,
+           GetHeaders (Headers h b)
+         ) => HasServer (Stream method framing ctype (Headers h b)) context where
 
-  type ServerT (Stream method framing ctype (Headers h (f a))) m = m (Headers h (f a))
+  type ServerT (Stream method framing ctype (Headers h b)) m = m (Headers h b)
   hoistServerWithContext _ _ nt s = nt s
 
   route Proxy _ = streamRouter (\x -> (getHeaders x, getResponse x)) method (Proxy :: Proxy framing) (Proxy :: Proxy ctype)
       where method = reflectMethod (Proxy :: Proxy method)
 
 
-streamRouter :: (MimeRender ctype a, FramingRender framing ctype, ToStreamGenerator f a) =>
-                (b -> ([(HeaderName, B.ByteString)], f a))
+streamRouter :: (MimeRender ctype a, FramingRender framing ctype, ToStreamGenerator b a) =>
+                (c -> ([(HeaderName, B.ByteString)], b))
              -> Method
              -> Proxy framing
              -> Proxy ctype
-             -> Delayed env (Handler b)
+             -> Delayed env (Handler c)
              -> Router env
 streamRouter splitHeaders method framingproxy ctypeproxy action = leafRouter $ \env request respond ->
           let accH    = fromMaybe ct_wildcard $ lookup hAccept $ requestHeaders request

servant/src/Servant/API.hs

@@ -117,8 +117,8 @@ import           Servant.API.Stream
                  (BoundaryStrategy (..), BuildFromStream (..),
                  ByteStringParser (..), FramingRender (..),
                  FramingUnrender (..), NetstringFraming, NewlineFraming,
-                 ResultStream (..), Stream, StreamGenerator (..), StreamGet,
-                 StreamPost, ToStreamGenerator (..))
+                 NoFraming, ResultStream (..), Stream, StreamGenerator (..),
+                 StreamGet, StreamPost, ToStreamGenerator (..))
 import           Servant.API.Sub
                  ((:>))
 import           Servant.API.Vault

servant/src/Servant/API/Stream.hs

@@ -2,6 +2,7 @@
 {-# LANGUAGE DeriveDataTypeable    #-}
 {-# LANGUAGE DeriveGeneric         #-}
 {-# LANGUAGE FlexibleInstances     #-}
+{-# LANGUAGE FunctionalDependencies #-}
 {-# LANGUAGE KindSignatures        #-}
 {-# LANGUAGE MultiParamTypeClasses #-}
 {-# LANGUAGE OverloadedStrings     #-}
@@ -38,13 +39,13 @@ type StreamGet  = Stream 'GET
 type StreamPost = Stream 'POST
 
 -- | Stream endpoints may be implemented as producing a @StreamGenerator@ -- a function that itself takes two emit functions -- the first to be used on the first value the stream emits, and the second to be used on all subsequent values (to allow interspersed framing strategies such as comma separation).
-newtype StreamGenerator a =  StreamGenerator {getStreamGenerator :: (a -> IO ()) -> (a -> IO ()) -> IO ()}
+newtype StreamGenerator a = StreamGenerator {getStreamGenerator :: (a -> IO ()) -> (a -> IO ()) -> IO ()}
 
 -- | ToStreamGenerator is intended to be implemented for types such as Conduit, Pipe, etc. By implementing this class, all such streaming abstractions can be used directly as endpoints.
-class ToStreamGenerator f a where
-   toStreamGenerator :: f a -> StreamGenerator a
+class ToStreamGenerator a b | a -> b where
+   toStreamGenerator :: a -> StreamGenerator b
 
-instance ToStreamGenerator StreamGenerator a
+instance ToStreamGenerator (StreamGenerator a) a
    where toStreamGenerator x = x
 
 -- | Clients reading from streaming endpoints can be implemented as producing a @ResultStream@ that captures the setup, takedown, and incremental logic for a read, being an IO continuation that takes a producer of Just either values or errors that terminates with a Nothing.
@@ -80,6 +81,18 @@ data ByteStringParser a = ByteStringParser {
 class FramingUnrender strategy a where
    unrenderFrames :: Proxy strategy -> Proxy a -> ByteStringParser (ByteStringParser (Either String ByteString))
 
+-- | A framing strategy that does not do any framing at all, it just passes the input data
+--   This will be used most of the time with binary data, such as files
+data NoFraming
+
+instance FramingRender NoFraming a where
+    header   _ _ = empty
+    boundary _ _ = BoundaryStrategyGeneral id
+    trailer  _ _ = empty
+
+instance FramingUnrender NoFraming a where
+    unrenderFrames _ _ = ByteStringParser (Just . (go,)) (go,)
+          where go = ByteStringParser (Just . (, empty) . Right) ((, empty) . Right)
 
 -- | A simple framing strategy that has no header or termination, and inserts a newline character between each frame.
 --   This assumes that it is used with a Content-Type that encodes without newlines (e.g. JSON).