Add EmptyForeignAPI and instance HasForeign ... EmptyAPI

doc/tutorial/Javascript.lhs

@@ -45,6 +45,7 @@ Now let's have the API type(s) and the accompanying datatypes.
 ``` haskell
 type API = "point" :> Get '[JSON] Point
       :<|> "books" :> QueryParam "q" Text :> Get '[JSON] (Search Book)
+      :<|> EmptyAPI
 
 type API' = API :<|> Raw
 
@@ -133,6 +134,7 @@ api' = Proxy
 server :: Server API
 server = randomPoint
     :<|> searchBook
+    :<|> emptyAPIServer
 
 server' :: Server API'
 server' = server

servant-foreign/src/Servant/Foreign/Internal.hs

@@ -187,6 +187,13 @@ instance (HasForeign lang ftype a, HasForeign lang ftype b)
          foreignFor lang ftype (Proxy :: Proxy a) req
     :<|> foreignFor lang ftype (Proxy :: Proxy b) req
 
+data EmptyForeignAPI = EmptyForeignAPI
+
+instance HasForeign lang ftype EmptyAPI where
+  type Foreign ftype EmptyAPI = EmptyForeignAPI
+
+  foreignFor Proxy Proxy Proxy _ = EmptyForeignAPI
+
 instance (KnownSymbol sym, HasForeignType lang ftype t, HasForeign lang ftype api)
   => HasForeign lang ftype (Capture sym t :> api) where
   type Foreign ftype (Capture sym t :> api) = Foreign ftype api
@@ -349,6 +356,9 @@ instance HasForeign lang ftype api
 class GenerateList ftype reqs where
   generateList :: reqs -> [Req ftype]
 
+instance GenerateList ftype EmptyForeignAPI where
+  generateList _ = []
+
 instance GenerateList ftype (Req ftype) where
   generateList r = [r]