Merge pull request #674 from phadej/delayed-cleanup-ioref-tests

Delayed cleanup ioref tests

servant-server/servant-server.cabal

@@ -109,6 +109,7 @@ test-suite spec
       Servant.ArbitraryMonadServerSpec
       Servant.Server.ErrorSpec
       Servant.Server.Internal.ContextSpec
+      Servant.Server.Internal.RoutingApplicationSpec
       Servant.Server.RouterSpec
       Servant.Server.StreamingSpec
       Servant.Server.UsingContextSpec

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

@@ -23,6 +23,7 @@ module Servant.Server.Internal
   , module Servant.Server.Internal.ServantErr
   ) where
 
+import           Control.Exception          (finally)
 import           Control.Monad.Trans        (liftIO)
 import qualified Data.ByteString            as B
 import qualified Data.ByteString.Char8      as BC8
@@ -400,8 +401,14 @@ instance HasServer Raw context where
   type ServerT Raw m = Application
 
   route Proxy _ rawApplication = RawRouter $ \ env request respond -> do
-    r <- runDelayed rawApplication env request
+    -- note: a Raw application doesn't register any cleanup
-    case r of
+    -- but for the sake of consistency, we nonetheless run
+    -- the cleanup once its done
+    cleanupRef <- newCleanupRef
+    r <- runDelayed rawApplication env request cleanupRef
+    go r request respond `finally` runCleanup cleanupRef
+
+    where go r request respond = case r of
             Route app   -> app request (respond . Route)
             Fail a      -> respond $ Fail a
             FailFatal e -> respond $ FailFatal e

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

@@ -6,10 +6,13 @@
 {-# LANGUAGE KindSignatures             #-}
 {-# LANGUAGE RecordWildCards            #-}
 {-# LANGUAGE StandaloneDeriving         #-}
+{-# LANGUAGE TupleSections              #-}
 module Servant.Server.Internal.RoutingApplication where
 
+import           Control.Exception                  (finally)
 import           Control.Monad                      (ap, liftM)
 import           Control.Monad.Trans                (MonadIO(..))
+import           Data.IORef                         (newIORef, readIORef, IORef, atomicModifyIORef)
 import           Network.Wai                        (Application, Request,
                                                      Response, ResponseReceived)
 import           Prelude                            ()
@@ -112,12 +115,33 @@ instance Functor (Delayed env) where
       , ..
       } -- Note [Existential Record Update]
 
+-- | A mutable cleanup action
+newtype CleanupRef = CleanupRef (IORef (IO ()))
+
+newCleanupRef :: IO CleanupRef
+newCleanupRef = CleanupRef <$> newIORef (return ())
+
+-- | Add a clean up action to a 'CleanupRef'
+addCleanup' :: IO () -> CleanupRef -> IO ()
+addCleanup' act (CleanupRef ref) = atomicModifyIORef ref (\act' -> (act' >> act, ()))
+
+addCleanup :: IO () -> DelayedIO ()
+addCleanup act = DelayedIO $ \_req cleanupRef ->
+  addCleanup' act cleanupRef >> return (Route ())
+
+-- | Run all the clean up actions registered in
+--   a 'CleanupRef'.
+runCleanup :: CleanupRef -> IO ()
+runCleanup (CleanupRef ref) = do
+  act <- readIORef ref
+  act
+
 -- | Computations used in a 'Delayed' can depend on the
 -- incoming 'Request', may perform 'IO, and result in a
 -- 'RouteResult, meaning they can either suceed, fail
 -- (with the possibility to recover), or fail fatally.
 --
-newtype DelayedIO a = DelayedIO { runDelayedIO :: Request -> IO (RouteResult a) }
+newtype DelayedIO a = DelayedIO { runDelayedIO :: Request -> CleanupRef -> IO (RouteResult a) }
 
 instance Functor DelayedIO where
   fmap = liftM
@@ -127,17 +151,17 @@ instance Applicative DelayedIO where
   (<*>) = ap
 
 instance Monad DelayedIO where
-  return x = DelayedIO (const $ return (Route x))
+  return x = DelayedIO (\_req _cleanup -> return (Route x))
   DelayedIO m >>= f =
-    DelayedIO $ \ req -> do
+    DelayedIO $ \ req cl -> do
-      r <- m req
+      r <- m req cl
       case r of
         Fail      e -> return $ Fail e
         FailFatal e -> return $ FailFatal e
-        Route     a -> runDelayedIO (f a) req
+        Route     a -> runDelayedIO (f a) req cl
 
 instance MonadIO DelayedIO where
-  liftIO m = DelayedIO (const $ Route <$> m)
+  liftIO m = DelayedIO (\_req _cl -> Route <$> m)
 
 -- | A 'Delayed' without any stored checks.
 emptyDelayed :: RouteResult a -> Delayed env a
@@ -148,15 +172,15 @@ emptyDelayed result =
 
 -- | Fail with the option to recover.
 delayedFail :: ServantErr -> DelayedIO a
-delayedFail err = DelayedIO (const $ return $ Fail err)
+delayedFail err = DelayedIO (\_req _cleanup -> return $ Fail err)
 
 -- | Fail fatally, i.e., without any option to recover.
 delayedFailFatal :: ServantErr -> DelayedIO a
-delayedFailFatal err = DelayedIO (const $ return $ FailFatal err)
+delayedFailFatal err = DelayedIO (\_req _cleanup -> return $ FailFatal err)
 
 -- | Gain access to the incoming request.
 withRequest :: (Request -> DelayedIO a) -> DelayedIO a
-withRequest f = DelayedIO (\ req -> runDelayedIO (f req) req)
+withRequest f = DelayedIO (\ req cl -> runDelayedIO (f req) req cl)
 
 -- | Add a capture to the end of the capture block.
 addCapture :: Delayed env (a -> b)
@@ -240,13 +264,18 @@ passToServer Delayed{..} x =
 runDelayed :: Delayed env a
            -> env
            -> Request
+           -> CleanupRef
            -> IO (RouteResult a)
-runDelayed Delayed{..} env = runDelayedIO $ do
+runDelayed Delayed{..} env req cleanupRef =
-  c <- capturesD env
+  runDelayedIO
+    (do c <- capturesD env
         methodD
         a <- authD
         b <- bodyD
-  DelayedIO (\ req -> return $ serverD c a b req)
+        DelayedIO $ \ r _cleanup -> return (serverD c a b r)
+    )
+    req
+    cleanupRef
 
 -- | Runs a delayed server and the resulting action.
 -- Takes a continuation that lets us send a response.
@@ -258,8 +287,11 @@ runAction :: Delayed env (Handler a)
           -> (RouteResult Response -> IO r)
           -> (a -> RouteResult Response)
           -> IO r
-runAction action env req respond k =
+runAction action env req respond k = do
-  runDelayed action env req >>= go >>= respond
+  cleanupRef <- newCleanupRef
+  (runDelayed action env req cleanupRef >>= go >>= respond)
+    `finally` runCleanup cleanupRef
+
   where
     go (Fail e)      = return $ Fail e
     go (FailFatal e) = return $ FailFatal e

servant-server/test/Servant/Server/Internal/RoutingApplicationSpec.hs

@@ -0,0 +1,61 @@
+module Servant.Server.Internal.RoutingApplicationSpec (spec) where
+
+import Prelude ()
+import Prelude.Compat
+
+import Control.Exception hiding (Handler)
+import Control.Monad.IO.Class
+import Data.Maybe (isJust)
+import Data.IORef
+import Servant.Server
+import Servant.Server.Internal.RoutingApplication
+import Test.Hspec
+
+import System.IO.Unsafe (unsafePerformIO)
+
+ok :: IO (RouteResult ())
+ok = return (Route ())
+
+-- Let's not write to the filesystem
+delayedTestRef :: IORef (Maybe String)
+delayedTestRef = unsafePerformIO $ newIORef Nothing
+
+delayed :: DelayedIO () -> RouteResult (Handler ()) -> Delayed () (Handler ())
+delayed body srv = Delayed
+  { capturesD = \() -> DelayedIO $ \_req _cl -> ok
+  , methodD = DelayedIO $ \_req_ _cl -> ok
+  , authD = DelayedIO $ \_req _cl -> ok
+  , bodyD = do
+      liftIO (writeIORef delayedTestRef (Just "hia") >> putStrLn "garbage created")
+      addCleanup (writeIORef delayedTestRef Nothing >> putStrLn "garbage collected")
+      body
+  , serverD = \() () _body _req -> srv
+  }
+
+simpleRun :: Delayed () (Handler ())
+          -> IO ()
+simpleRun d = fmap (either ignoreE id) . try $
+  runAction d () undefined (\_ -> return ()) (\_ -> FailFatal err500)
+
+  where ignoreE :: SomeException -> ()
+        ignoreE = const ()
+
+spec :: Spec
+spec = do
+  describe "Delayed" $ do
+    it "actually runs clean up actions" $ do
+      _ <- simpleRun $ delayed (return ()) (Route $ return ())
+      cleanUpDone <- isJust <$> readIORef delayedTestRef
+      cleanUpDone `shouldBe` False
+    it "even with exceptions in serverD" $ do
+      _ <- simpleRun $ delayed (return ()) (Route $ throw DivideByZero)
+      cleanUpDone <- isJust <$> readIORef delayedTestRef
+      cleanUpDone `shouldBe` False
+    it "even with routing failure in bodyD" $ do
+      _ <- simpleRun $ delayed (delayedFailFatal err500) (Route $ return ())
+      cleanUpDone <- isJust <$> readIORef delayedTestRef
+      cleanUpDone `shouldBe` False
+    it "even with exceptions in bodyD" $ do
+      _ <- simpleRun $ delayed (liftIO $ throwIO DivideByZero) (Route $ return ())
+      cleanUpDone <- isJust <$> readIORef delayedTestRef
+      cleanUpDone `shouldBe` False