Clean up column table code

lib/Database/PostgreSQL/Opium/Error.hs

@@ -1,15 +1,21 @@
-module Database.PostgreSQL.Opium.Error (Error (..)) where
+module Database.PostgreSQL.Opium.Error (Error (..), ErrorPosition (..)) where
 
+import Control.Exception (Exception)
 import Data.Text (Text)
 import Database.PostgreSQL.LibPQ (ExecStatus, Oid, Row)
 
-import Database.PostgreSQL.Opium.FromField (FieldError)
+data ErrorPosition = ErrorPosition
+  { errorPositionRow :: Row
+  , errorPositionColumn :: Text
+  } deriving (Eq, Show)
 
 data Error
-  = ErrorDecode Row Text FieldError
-  | ErrorNoResult
+  = ErrorNoResult
   | ErrorInvalidResult ExecStatus Text
   | ErrorMissingColumn Text
   | ErrorInvalidOid Text Oid
-  | ErrorUnexpectedNull Row Text
+  | ErrorUnexpectedNull ErrorPosition
+  | ErrorInvalidField ErrorPosition Oid Text String
   deriving (Eq, Show)
+
+instance Exception Error where

lib/Database/PostgreSQL/Opium/FromField.hs

@@ -3,8 +3,7 @@
 {-# LANGUAGE TypeApplications #-}
 
 module Database.PostgreSQL.Opium.FromField
-  ( FieldError (..)
-  , FromField (..)
+  ( FromField (..)
   , fromField
   ) where
 
@@ -25,23 +24,15 @@ import Database.PostgreSQL.LibPQ (Oid)
 import GHC.Float (double2Float)
 
 import qualified Data.Text as Text
+
 import qualified Database.PostgreSQL.Opium.Oid as Oid
 
 (\/) :: (a -> Bool) -> (a -> Bool) -> a -> Bool
 p \/ q = \x -> p x || q x
 
-data FieldError
-  = FieldErrorUnexpectedNull
-  | FieldErrorInvalidField Oid Text String
-  deriving (Eq, Show)
-
-mapLeft :: (b -> c) -> Either b a -> Either c a
-mapLeft f (Left l) = Left $ f l
-mapLeft _ (Right r) = Right r
-
-fromField :: FromField a => Oid -> Text -> Either FieldError a
-fromField oid field =
-  mapLeft (FieldErrorInvalidField oid field) $ parseOnly parseField field
+fromField :: FromField a => Text -> Either String a
+fromField =
+  parseOnly parseField
 
 class FromField a where
   validOid :: Proxy a -> Oid -> Bool