Add parameter-supplying operator

Renamed `(/:)` to `(//)`, and used `(/:)` for supplying parameters to
client functions.

Should close #1442.

Author: Gaël Deest

servant-client-core/src/Servant/Client/Core/HasClient.hs

@@ -27,6 +27,7 @@ module Servant.Client.Core.HasClient (
     HasClient (..),
     EmptyClient (..),
     AsClientT,
+    (//),
     (/:),
     foldMapUnion,
     matchUnion,
@@ -54,7 +55,8 @@ import           Data.Sequence
                  (fromList)
 import qualified Data.Text                       as T
 import           Network.HTTP.Media
-                 (MediaType, matches, parseAccept, (//))
+                 (MediaType, matches, parseAccept)
+import qualified Network.HTTP.Media as Media
 import qualified Data.Sequence as Seq
 import           Data.SOP.BasicFunctors
                  (I (I), (:.:) (Comp))
@@ -873,9 +875,12 @@ instance
 
 #endif
 
-infixl 1 /:
+infixl 1 //
+infixl 2 /:
 
--- | Convenience function for working with nested record-clients.
+-- | Helper to make code using records of clients more readable.
+--
+-- Can be mixed with (/:) for supplying arguments.
 --
 -- Example:
 --
@@ -899,10 +904,46 @@ infixl 1 /:
 -- rootClient = client api
 --
 -- endpointClient :: ClientM Person
--- endpointClient = client /: subApi /: endpoint
+-- endpointClient = client // subApi // endpoint
+-- @@
+(//) :: a -> (a -> b) -> b
+x // f = f x
+
+-- | Convenience function for supplying arguments to client functions when
+-- working with records of clients.
+--
+-- Intended to be use in conjunction with '(//)'.
+--
+-- Example:
+--
+-- @@
+-- type Api = NamedAPI RootApi
+--
+-- data RootApi mode = RootApi
+--   { subApi :: mode :- Capture "token" String :> NamedAPI SubApi
+--   , hello :: mode :- Capture "name" String :> Get '[JSON] String
+--   , …
+--   } deriving Generic
+--
+-- data SubAmi mode = SubApi
+--   { endpoint :: mode :- Get '[JSON] Person
+--   , …
+--   } deriving Generic
+--
+-- api :: Proxy API
+-- api = Proxy
+--
+-- rootClient :: RootApi (AsClientT ClientM)
+-- rootClient = client api
+--
+-- hello :: String -> ClientM String
+-- hello name = rootClient // hello /: name
+--
+-- endpointClient :: ClientM Person
+-- endpointClient = client // subApi /: "foobar123" // endpoint
 -- @@
-(/:) :: a -> (a -> b) -> b
-x /: f = f x
+(/:) :: (a -> b -> c) -> b -> a -> c
+(/:) = flip
 
 
 {- Note [Non-Empty Content Types]
@@ -928,7 +969,7 @@ for empty and one for non-empty lists).
 checkContentTypeHeader :: RunClient m => Response -> m MediaType
 checkContentTypeHeader response =
   case lookup "Content-Type" $ toList $ responseHeaders response of
-    Nothing -> return $ "application"//"octet-stream"
+    Nothing -> return $ "application" Media.// "octet-stream"
     Just t -> case parseAccept t of
       Nothing -> throwClientError $ InvalidContentTypeHeader response
       Just t' -> return t'

servant-client-core/src/Servant/Client/Core/Reexport.hs

@@ -8,6 +8,7 @@ module Servant.Client.Core.Reexport
   , foldMapUnion
   , matchUnion
   , AsClientT
+  , (//)
   , (/:)
 
     -- * Response (for @Raw@)

servant-client/test/Servant/ClientTestUtils.hs

@@ -111,7 +111,7 @@ type TestHeaders = '[Header "X-Example1" Int, Header "X-Example2" String]
 data RecordRoutes mode = RecordRoutes
   { version :: mode :- "version" :> Get '[JSON] Int
   , echo :: mode :- "echo" :> Capture "string" String :> Get '[JSON] String
-  , otherRoutes :: mode :- "other" :> NamedRoutes OtherRoutes
+  , otherRoutes :: mode :- "other" :> Capture "someParam" Int :> NamedRoutes OtherRoutes
   } deriving Generic
 
 data OtherRoutes mode = OtherRoutes
@@ -246,7 +246,7 @@ server = serve api (
   :<|> RecordRoutes
          { version = pure 42
          , echo = pure
-         , otherRoutes = OtherRoutes
+         , otherRoutes = \_ -> OtherRoutes
              { something = pure ["foo", "bar", "pweet"]
              }
          }

servant-client/test/Servant/GenericSpec.hs

@@ -19,7 +19,7 @@ module Servant.GenericSpec (spec) where
 
 import           Test.Hspec
 
-import           Servant.Client ((/:))
+import           Servant.Client ((//), (/:))
 import           Servant.ClientTestUtils
 
 spec :: Spec
@@ -31,7 +31,7 @@ genericSpec = beforeAll (startWaiApp server) $ afterAll endWaiApp $ do
   context "Record clients work as expected" $ do
 
     it "Client functions return expected values" $ \(_,baseUrl) -> do
-      runClient (recordRoutes /: version) baseUrl `shouldReturn` Right 42
-      runClient (recordRoutes /: echo $ "foo") baseUrl `shouldReturn` Right "foo"
+      runClient (recordRoutes // version) baseUrl `shouldReturn` Right 42
+      runClient (recordRoutes // echo /: "foo") baseUrl `shouldReturn` Right "foo"
     it "Clients can be nested" $ \(_,baseUrl) -> do
-      runClient (recordRoutes /: otherRoutes /: something) baseUrl `shouldReturn` Right ["foo", "bar", "pweet"]
+      runClient (recordRoutes // otherRoutes /: 42 // something) baseUrl `shouldReturn` Right ["foo", "bar", "pweet"]