Add actual row number to row number errors

lib/Database/PostgreSQL/Opium.hs

@@ -59,11 +59,11 @@ instance RowContainer Maybe where
   extract result nRows columnTable
     | nRows == 0 = pure Nothing
     | nRows == 1 = Just <$> ExceptT (fromRow result columnTable 0)
-    | otherwise = throwE ErrorMoreThanOneRow
+    | otherwise = throwE $ ErrorMoreThanOneRow $ fromEnum nRows
 
 instance RowContainer Identity where
   extract result nRows columnTable = do
-    unless (nRows == 1) $ throwE ErrorNotExactlyOneRow
+    unless (nRows == 1) $ throwE $ ErrorNotExactlyOneRow $ fromEnum nRows
     Identity <$> ExceptT (fromRow result columnTable 0)
 
 -- The order of the type parameters is important, because it is more common to use type applications for providing the row type and row container type.

lib/Database/PostgreSQL/Opium/Connection.hs

@@ -12,6 +12,7 @@ module Database.PostgreSQL.Opium.Connection
   ) where
 
 import Control.Concurrent.MVar (MVar, newMVar, modifyMVar_, withMVar)
+import Control.Exception (Exception)
 import Data.Maybe (fromMaybe)
 import Data.Text (Text)
 import Database.PostgreSQL.LibPQ (ConnStatus (..))
@@ -27,6 +28,8 @@ newtype Connection = Connection
 newtype ConnectionError = ConnectionError Text
   deriving (Show)
 
+instance Exception ConnectionError
+
 withRawConnection
   :: HasCallStack
   => (Maybe LibPQ.Connection -> IO a)

lib/Database/PostgreSQL/Opium/Error.hs

@@ -17,8 +17,8 @@ data Error
   | ErrorInvalidOid Text Oid
   | ErrorUnexpectedNull ErrorPosition
   | ErrorInvalidField ErrorPosition Oid ByteString String
-  | ErrorNotExactlyOneRow
-  | ErrorMoreThanOneRow
+  | ErrorNotExactlyOneRow Int
+  | ErrorMoreThanOneRow Int
   | ErrorConnectionClosed
   deriving (Eq, Show)