Distilled ErrorHandling bug to simple catchIter bug

yesod-core/Yesod/Handler.hs

@@ -164,6 +164,7 @@ import Data.Text (Text)
 import Yesod.Message (RenderMessage (..))
 
 import Text.Blaze (toHtml, preEscapedText)
+import Yesod.Internal.TestApi (catchIter)
 
 -- | The type-safe URLs associated with a site argument.
 type family Route a
@@ -420,12 +421,6 @@ runHandler handler mrender sroute tomr ma sa =
                 finalSession
         HCWai r -> return $ YARWai r
 
-catchIter :: Exception e
-          => Iteratee ByteString IO a
-          -> (e -> Iteratee ByteString IO a)
-          -> Iteratee ByteString IO a
-catchIter (Iteratee mstep) f = Iteratee $ mstep `E.catch` (runIteratee . f)
-
 safeEh :: ErrorResponse -> YesodApp
 safeEh er = YesodApp $ \_ _ _ session -> do
     liftIO $ hPutStrLn stderr $ "Error handler errored out: " ++ show er

yesod-core/Yesod/Internal/TestApi.hs

@@ -6,6 +6,17 @@
 --
 module Yesod.Internal.TestApi
   ( randomString, parseWaiRequest'
+  , catchIter
   ) where
 
 import Yesod.Internal.Request (randomString, parseWaiRequest')
+import Control.Exception (Exception, catch)
+import Data.Enumerator (Iteratee (..))
+import Data.ByteString (ByteString)
+import Prelude hiding (catch)
+
+catchIter :: Exception e
+          => Iteratee ByteString IO a
+          -> (e -> Iteratee ByteString IO a)
+          -> Iteratee ByteString IO a
+catchIter (Iteratee mstep) f = Iteratee $ mstep `catch` (runIteratee . f)

yesod-core/test/Test/ErrorHandling.hs

@@ -11,6 +11,10 @@ import Network.Wai.Test
 import Text.Hamlet (hamlet)
 import qualified Data.ByteString.Lazy as L
 import qualified Data.ByteString.Char8 as S8
+import Yesod.Internal.TestApi
+import qualified Data.Enumerator as E
+import qualified Data.Enumerator.List as EL
+import Control.Exception (SomeException)
 
 data App = App
 
@@ -57,6 +61,7 @@ errorHandlingTest = describe "Test.ErrorHandling"
     [ it "says not found" caseNotFound
     , it "says 'There was an error' before runRequestBody" caseBefore
     , it "says 'There was an error' after runRequestBody" caseAfter
+    , it "catchIter handles internal exceptions" caseCatchIter
     ]
 
 runner :: Session () -> IO ()
@@ -96,3 +101,11 @@ caseAfter = runner $ do
         }
     assertStatus 500 res
     assertBodyContains "There was an error 2.71828" res
+
+caseCatchIter :: IO ()
+caseCatchIter = E.run_ $ E.enumList 8 (replicate 1000 "foo") E.$$ flip catchIter ignorer $ do
+    _ <- EL.consume
+    error "foo"
+  where
+    ignorer :: SomeException -> E.Iteratee a IO ()
+    ignorer _ = return ()