Add MonadCatch and MonadMask instances to RouteResultT and DelayedIO

Fix #1829

Author: tchoutri

servant-server/src/Servant/Server/Internal/DelayedIO.hs

@@ -5,7 +5,7 @@
 module Servant.Server.Internal.DelayedIO where
 
 import Control.Monad.Base (MonadBase (..))
-import Control.Monad.Catch (MonadThrow (..))
+import Control.Monad.Catch (MonadThrow (..), MonadCatch(..), MonadMask)
 import Control.Monad.Reader (MonadReader (..), ReaderT (..), runReaderT)
 import Control.Monad.Trans (MonadIO (..), MonadTrans (..))
 import Control.Monad.Trans.Control (MonadBaseControl (..))
@@ -34,6 +34,8 @@ newtype DelayedIO a = DelayedIO {runDelayedIO' :: ReaderT Request (ResourceT (Ro
     , MonadReader Request
     , MonadResource
     , MonadThrow
+    , MonadCatch
+    , MonadMask
     )
 
 instance MonadBase IO DelayedIO where
@@ -53,6 +55,7 @@ instance MonadBaseControl IO DelayedIO where
       runInBase (runInternalState (runReaderT (runDelayedIO' x) req) s)
   restoreM = DelayedIO . lift . withInternalState . const . restoreM
 
+
 runDelayedIO :: DelayedIO a -> Request -> ResourceT IO (RouteResult a)
 runDelayedIO m req = transResourceT runRouteResultT $ runReaderT (runDelayedIO' m) req
 

servant-server/src/Servant/Server/Internal/RouteResult.hs

@@ -8,7 +8,7 @@ module Servant.Server.Internal.RouteResult where
 
 import Control.Monad (ap)
 import Control.Monad.Base (MonadBase (..))
-import Control.Monad.Catch (MonadThrow (..))
+import Control.Monad.Catch (ExitCase (..), MonadCatch (..), MonadMask (..), MonadThrow (..))
 import Control.Monad.Trans (MonadIO (..), MonadTrans (..))
 import Control.Monad.Trans.Control
   ( ComposeSt
@@ -75,3 +75,43 @@ instance MonadTransControl RouteResultT where
 
 instance MonadThrow m => MonadThrow (RouteResultT m) where
   throwM = lift . throwM
+
+instance MonadCatch m => MonadCatch (RouteResultT m) where
+  catch (RouteResultT m) f = RouteResultT $ catch m (runRouteResultT . f)
+
+instance MonadMask m => MonadMask (RouteResultT m) where
+  mask f = RouteResultT $ mask $ \u -> runRouteResultT $ f (q u)
+    where
+      q
+        :: (m (RouteResult a) -> m (RouteResult a))
+        -> RouteResultT m a
+        -> RouteResultT m a
+      q u (RouteResultT b) = RouteResultT (u b)
+  uninterruptibleMask f = RouteResultT $ uninterruptibleMask $ \u -> runRouteResultT $ f (q u)
+    where
+      q
+        :: (m (RouteResult a) -> m (RouteResult a))
+        -> RouteResultT m a
+        -> RouteResultT m a
+      q u (RouteResultT b) = RouteResultT (u b)
+
+  generalBracket acquire release use = RouteResultT $ do
+    (eb, ec) <-
+      generalBracket
+        (runRouteResultT acquire)
+        ( \resourceRoute exitCase -> case resourceRoute of
+            Fail e -> pure $ Fail e -- nothing to release, acquire didn't succeed
+            FailFatal e -> pure $ FailFatal e
+            Route resource -> case exitCase of
+              ExitCaseSuccess (Route b) -> runRouteResultT (release resource (ExitCaseSuccess b))
+              ExitCaseException e -> runRouteResultT (release resource (ExitCaseException e))
+              _ -> runRouteResultT (release resource ExitCaseAbort)
+        )
+        ( \case
+            Fail e -> pure $ Fail e -- nothing to release, acquire didn't succeed
+            FailFatal e -> pure $ FailFatal e
+            Route resource -> runRouteResultT (use resource)
+        )
+    -- The order in which we perform those two effects doesn't matter,
+    -- since the error message is the same regardless.
+    pure ((,) <$> eb <*> ec)