git.iko.soy/servant
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Merge pull request #736 from phadej/entered

Redo Enter

commitd0048057cd1bb9fc7aece8f2ee35053e3477660f authorOleg Grenrus <oleg.grenrus@iki.fi> dateFri 5 May 2017, 10:17 (9 years ago) parentf26a2d1c01dca6
3 files changed+32−10
compare with master
unifiedsplit
servant-server/src/Servant/Server.hs+3−2 servant-server/test/Servant/ArbitraryMonadServerSpec.hs+2−1 servant/src/Servant/Utils/Enter.hs+27−7
servant-server/src/Servant/Server.hs+3−2
@@ -207,7 +207,7 @@ layoutWithContext p context =
207207-- monad. Or have your types ensure that your handlers don't do any IO. Enter
208208-- `enter`.
209209--
210−-- With `enter`, you can provide a function, wrapped in the `(:~>)` / `Nat`
210+-- With `enter`, you can provide a function, wrapped in the `(:~>)` / `NT`
211211-- newtype, to convert any number of endpoints from one type constructor to
212212-- another. For example
213213--
@@ -215,7 +215,8 @@ layoutWithContext p context =
215215-- >>> import qualified Control.Category as C
216216-- >>> type ReaderAPI = "ep1" :> Get '[JSON] Int :<|> "ep2" :> Get '[JSON] String
217217-- >>> let readerServer = return 1797 :<|> ask :: ServerT ReaderAPI (Reader String)
218−-- >>> let mainServer = enter (generalizeNat C.. (runReaderTNat "hi")) readerServer :: Server ReaderAPI
218+-- >>> let nt = generalizeNat C.. (runReaderTNat "hi") :: Reader String :~> Handler
219+-- >>> let mainServer = enter nt readerServer :: Server ReaderAPI
219220--
220221
221222-- $setup
servant-server/test/Servant/ArbitraryMonadServerSpec.hs+2−1
@@ -5,6 +5,7 @@ module Servant.ArbitraryMonadServerSpec where
55
66import qualified Control.Category as C
77import Control.Monad.Reader
8+import Data.Functor.Identity
89import Data.Proxy
910import Servant.API
1011import Servant.Server
@@ -40,7 +41,7 @@ readerServer :: Server ReaderAPI
4041readerServer = enter fReader readerServer'
4142
4243combinedReaderServer' :: ServerT CombinedAPI (Reader String)
43−combinedReaderServer' = readerServer' :<|> enter generalizeNat (return True)
44+combinedReaderServer' = readerServer' :<|> enter (generalizeNat :: Identity :~> Reader String) (return True)
4445
4546combinedReaderServer :: Server CombinedAPI
4647combinedReaderServer = enter fReader combinedReaderServer'
servant/src/Servant/Utils/Enter.hs+27−7
@@ -27,21 +27,41 @@ import Prelude.Compat
2727
2828import Servant.API
2929
30−class Enter typ arg ret | typ arg -> ret, typ ret -> arg where
31− enter :: arg -> typ -> ret
30+type family Entered m n api where
31+ Entered m n (m a) = n a
32+ Entered m n (a -> api) = a -> Entered m n api
33+ Entered m n (api1 :<|> api2) = Entered m n api1 :<|> Entered m n api2
34+
35+class ( Entered m n typ ~ ret
36+ , Entered n m ret ~ typ
37+ )
38+ => Enter typ m n ret
39+ where
40+ enter :: (m :~> n) -> typ -> ret
3241
3342-- ** Servant combinators
34−instance ( Enter typ1 arg1 ret1, Enter typ2 arg2 ret2
35− , arg1 ~ arg2
36− ) => Enter (typ1 :<|> typ2) arg1 (ret1 :<|> ret2) where
43+
44+instance
45+ ( Entered m1 n1 (typ1 :<|> typ2) ~ (ret1 :<|> ret2)
46+ , Entered n1 m1 (ret1 :<|> ret2) ~ (typ1 :<|> typ2)
47+ , Enter typ1 m1 n1 ret1, Enter typ2 m2 n2 ret2
48+ , m1 ~ m2, n1 ~ n2
49+ ) => Enter (typ1 :<|> typ2) m1 n1 (ret1 :<|> ret2)
50+ where
3751 enter e (a :<|> b) = enter e a :<|> enter e b
3852
39−instance (Enter b arg ret) => Enter (a -> b) arg (a -> ret) where
53+instance
54+ ( Entered m n (a -> typ) ~ (a -> ret)
55+ , Entered n m (a -> ret) ~ (a -> typ)
56+ , Enter typ m n ret
57+ )
58+ => Enter (a -> typ) m n (a -> ret)
59+ where
4060 enter arg f a = enter arg (f a)
4161
4262-- ** Useful instances
4363
44−instance Enter (m a) (m :~> n) (n a) where
64+instance Enter (m a) m n (n a) where
4565 enter (NT f) = f
4666
4767-- | Like `lift`.