fix metadata log simplifier and additional quickcheck tests

Logs/MetaData.hs

@@ -119,7 +119,7 @@ addMetaData k metadata = do
  -
  - So, the only simplication that is actually done is to throw out an
  - old line when all the values in it have been overridden by lines that
- - came before
+ - came after.
  -}
 simplifyLog :: Log MetaData -> Log MetaData
 simplifyLog s = case S.toDescList s of
@@ -128,7 +128,7 @@ simplifyLog s = case S.toDescList s of
   where
 	go c _ [] = c
 	go c newer (l:ls)
-		| older `hasUniqueMetaData` newer =
+		| hasUniqueMetaData newer older =
 			go (l:c) (unionMetaData older newer) ls
 		| otherwise = go c newer ls
 	  where

Test.hs

@@ -145,7 +145,7 @@ properties = localOption (QuickCheckTests 1000) $ testGroup "QuickCheck"
 	, testProperty "prop_hashes_stable" Utility.Hash.prop_hashes_stable
 	, testProperty "prop_schedule_roundtrips" Utility.Scheduled.prop_schedule_roundtrips
 	, testProperty "prop_duration_roundtrips" Utility.HumanTime.prop_duration_roundtrips
-	, testProperty "prop_updateMetaData_sane" Types.MetaData.prop_updateMetaData_sane
+	, testProperty "prop_metadata_sane" Types.MetaData.prop_metadata_sane
 	, testProperty "prop_metadata_serialize" Types.MetaData.prop_metadata_serialize
 	]
 

Types/MetaData.hs

@@ -29,7 +29,7 @@ module Types.MetaData (
 	getAllMetaData,
 	serialize,
 	deserialize,
-	prop_updateMetaData_sane,
+	prop_metadata_sane,
 	prop_metadata_serialize
 ) where
 
@@ -199,10 +199,13 @@ instance Arbitrary MetaValue where
 instance Arbitrary MetaField where
 	arbitrary = MetaField <$> arbitrary `suchThat` legalField 
 
-prop_updateMetaData_sane :: MetaData -> MetaField -> MetaValue -> Bool
-prop_updateMetaData_sane m f v = and
+prop_metadata_sane :: MetaData -> MetaField -> MetaValue -> Bool
+prop_metadata_sane m f v = and
 	[ S.member v $ getAllMetaData f m'
 	, not (isSet v) || S.member v (currentMetaDataValues f m')
+	, not (hasUniqueMetaData m m)
+	, hasUniqueMetaData newMetaData m'
+	, not (hasUniqueMetaData m' newMetaData)
 	]
   where
 	m' = updateMetaData f v m