From e77e056f5b8ecfb5a257764268d092d23319a039 Mon Sep 17 00:00:00 2001
From: Danny B <danny.b.eml@gmail.com>
Date: Thu, 8 Aug 2013 16:46:01 +1100
Subject: [PATCH] Handle NULL result in avg_ too.

---
 src/Database/Esqueleto.hs                   | 3 ++-
 src/Database/Esqueleto/Internal/Language.hs | 3 ++-
 test/Test.hs                                | 4 ++--
 3 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/src/Database/Esqueleto.hs b/src/Database/Esqueleto.hs
index f1764a8..35b4c6a 100644
--- a/src/Database/Esqueleto.hs
+++ b/src/Database/Esqueleto.hs
@@ -43,7 +43,8 @@ module Database.Esqueleto
              , val, isNothing, just, nothing, joinV, countRows, count, not_
              , (==.), (>=.), (>.), (<=.), (<.), (!=.), (&&.), (||.)
              , (+.), (-.), (/.), (*.)
-             , random_, sum_, round_, ceiling_, floor_, avg_, min_, max_
+             , random_, round_, ceiling_, floor_
+             , min_, max_,_sum_, avg_,
              , like, (%), concat_, (++.)
              , subList_select, subList_selectDistinct, valList
              , in_, notIn, exists, notExists
diff --git a/src/Database/Esqueleto/Internal/Language.hs b/src/Database/Esqueleto/Internal/Language.hs
index ea686b0..ebc220d 100644
--- a/src/Database/Esqueleto/Internal/Language.hs
+++ b/src/Database/Esqueleto/Internal/Language.hs
@@ -240,10 +240,11 @@ class (Functor query, Applicative query, Monad query) =>
   round_   :: (PersistField a, PersistField b) => expr (Value a) -> expr (Value b)
   ceiling_ :: (PersistField a, PersistField b) => expr (Value a) -> expr (Value b)
   floor_   :: (PersistField a, PersistField b) => expr (Value a) -> expr (Value b)
+
   sum_     :: (PersistField a) => expr (Value a) -> expr (Value (Maybe a))
   min_     :: (PersistField a) => expr (Value a) -> expr (Value (Maybe a))
   max_     :: (PersistField a) => expr (Value a) -> expr (Value (Maybe a))
-  avg_     :: (PersistField a, PersistField b) => expr (Value a) -> expr (Value b)
+  avg_     :: (PersistField a, PersistField b) => expr (Value a) -> expr (Value (Maybe b))
 
   -- | @LIKE@ operator.
   like :: (PersistField s, IsString s) => expr (Value s) -> expr (Value s) -> expr (Value Bool)
diff --git a/test/Test.hs b/test/Test.hs
index ecc3b1a..3d92243 100644
--- a/test/Test.hs
+++ b/test/Test.hs
@@ -285,8 +285,8 @@ main = do
           _ <- insert' p4
           ret <- select $
                  from $ \p->
-                 return $ avg_ (p ^. PersonAge)
-          liftIO $ ret `shouldBe` [ Value ((36 + 17 + 17) / 3 :: Double) ]
+                 return $ joinV $ avg_ (p ^. PersonAge)
+          liftIO $ ret `shouldBe` [ Value $ Just ((36 + 17 + 17) / 3 :: Double) ]
 
       it "works with min_" $
         run $ do