Merge pull request #736 from phadej/entered

Redo Enter
This commit is contained in:
Oleg Grenrus 2017-05-05 10:17:34 +03:00 committed by GitHub
commit d0048057cd
3 changed files with 32 additions and 10 deletions

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@ -207,7 +207,7 @@ layoutWithContext p context =
-- monad. Or have your types ensure that your handlers don't do any IO. Enter
-- `enter`.
--
-- With `enter`, you can provide a function, wrapped in the `(:~>)` / `Nat`
-- With `enter`, you can provide a function, wrapped in the `(:~>)` / `NT`
-- newtype, to convert any number of endpoints from one type constructor to
-- another. For example
--
@ -215,7 +215,8 @@ layoutWithContext p context =
-- >>> import qualified Control.Category as C
-- >>> type ReaderAPI = "ep1" :> Get '[JSON] Int :<|> "ep2" :> Get '[JSON] String
-- >>> let readerServer = return 1797 :<|> ask :: ServerT ReaderAPI (Reader String)
-- >>> let mainServer = enter (generalizeNat C.. (runReaderTNat "hi")) readerServer :: Server ReaderAPI
-- >>> let nt = generalizeNat C.. (runReaderTNat "hi") :: Reader String :~> Handler
-- >>> let mainServer = enter nt readerServer :: Server ReaderAPI
--
-- $setup

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@ -5,6 +5,7 @@ module Servant.ArbitraryMonadServerSpec where
import qualified Control.Category as C
import Control.Monad.Reader
import Data.Functor.Identity
import Data.Proxy
import Servant.API
import Servant.Server
@ -40,7 +41,7 @@ readerServer :: Server ReaderAPI
readerServer = enter fReader readerServer'
combinedReaderServer' :: ServerT CombinedAPI (Reader String)
combinedReaderServer' = readerServer' :<|> enter generalizeNat (return True)
combinedReaderServer' = readerServer' :<|> enter (generalizeNat :: Identity :~> Reader String) (return True)
combinedReaderServer :: Server CombinedAPI
combinedReaderServer = enter fReader combinedReaderServer'

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@ -27,21 +27,41 @@ import Prelude.Compat
import Servant.API
class Enter typ arg ret | typ arg -> ret, typ ret -> arg where
enter :: arg -> typ -> ret
type family Entered m n api where
Entered m n (m a) = n a
Entered m n (a -> api) = a -> Entered m n api
Entered m n (api1 :<|> api2) = Entered m n api1 :<|> Entered m n api2
class ( Entered m n typ ~ ret
, Entered n m ret ~ typ
)
=> Enter typ m n ret
where
enter :: (m :~> n) -> typ -> ret
-- ** Servant combinators
instance ( Enter typ1 arg1 ret1, Enter typ2 arg2 ret2
, arg1 ~ arg2
) => Enter (typ1 :<|> typ2) arg1 (ret1 :<|> ret2) where
instance
( Entered m1 n1 (typ1 :<|> typ2) ~ (ret1 :<|> ret2)
, Entered n1 m1 (ret1 :<|> ret2) ~ (typ1 :<|> typ2)
, Enter typ1 m1 n1 ret1, Enter typ2 m2 n2 ret2
, m1 ~ m2, n1 ~ n2
) => Enter (typ1 :<|> typ2) m1 n1 (ret1 :<|> ret2)
where
enter e (a :<|> b) = enter e a :<|> enter e b
instance (Enter b arg ret) => Enter (a -> b) arg (a -> ret) where
instance
( Entered m n (a -> typ) ~ (a -> ret)
, Entered n m (a -> ret) ~ (a -> typ)
, Enter typ m n ret
)
=> Enter (a -> typ) m n (a -> ret)
where
enter arg f a = enter arg (f a)
-- ** Useful instances
instance Enter (m a) (m :~> n) (n a) where
instance Enter (m a) m n (n a) where
enter (NT f) = f
-- | Like `lift`.