Change definition of StreamGenerator

Author: jvanbruegge

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/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.