83078ea · typeable/aeson

git.iko.soy/typeable/aeson

Added eitherDecode and eitherDecode'

They are just like decode and decode' respectively but return an error message when decoding fails.

commit83078ea3b22142ee540d901cb8d4124989cdcda7 authorBas van Dijk <v.dijk.bas@gmail.com> dateMon 13 Feb 2012, 11:22 (15 years ago) parent5079559

2 files changed+23−1

compare with master

unifiedsplit

Data/Aeson.hs+13−1 Data/Aeson/Parser/Internal.hs+10

Data/Aeson.hs+13−1

@@ -16,6 +16,8 @@ module Data.Aeson

1616 -- * Encoding and decoding

1717 decode

1818 , decode'

19+ , eitherDecode

20+ , eitherDecode'

1921 , encode

2022 -- * Core JSON types

2123 , Value(..)

@@ -40,7 +42,7 @@ module Data.Aeson

4042 ) where

4143

4244import Data.Aeson.Encode (encode)

43−import Data.Aeson.Parser.Internal (decodeWith, json, json')

45+import Data.Aeson.Parser.Internal (decodeWith, eitherDecodeWith, json, json')

4446import Data.Aeson.Types

4547import qualified Data.ByteString.Lazy as L

4648

@@ -63,3 +65,13 @@ decode = decodeWith json fromJSON

6365decode' :: (FromJSON a) => L.ByteString -> Maybe a

6466decode' = decodeWith json' fromJSON

6567{-# INLINE decode' #-}

68+

69+-- | Like 'decode' but returns an error message when decoding fails.

70+eitherDecode :: (FromJSON a) => L.ByteString -> Either String a

71+eitherDecode = eitherDecodeWith json fromJSON

72+{-# INLINE eitherDecode #-}

73+

74+-- | Like 'decode'' but returns an error message when decoding fails.

75+eitherDecode' :: (FromJSON a) => L.ByteString -> Either String a

76+eitherDecode' = eitherDecodeWith json' fromJSON

77+{-# INLINE eitherDecode' #-}

Data/Aeson/Parser/Internal.hs+10

@@ -23,6 +23,7 @@ module Data.Aeson.Parser.Internal

2323 , value'

2424 -- * Helpers

2525 , decodeWith

26+ , eitherDecodeWith

2627 ) where

2728

2829import Blaze.ByteString.Builder (fromByteString, toByteString)

@@ -238,6 +239,15 @@ decodeWith p to s =

238239 _ -> Nothing

239240{-# INLINE decodeWith #-}

240241

242+eitherDecodeWith :: Parser Value -> (Value -> Result a) -> L.ByteString -> Either String a

243+eitherDecodeWith p to s =

244+ case L.parse p s of

245+ L.Done _ v -> case to v of

246+ Success a -> Right a

247+ Error msg -> Left msg

248+ L.Fail _ _ msg -> Left msg

249+{-# INLINE eitherDecodeWith #-}

250+

241251-- $lazy

242252--

243253-- The 'json' and 'value' parsers decouple identification from