git-annex/Utility/Aeson.hs
Joey Hess 76362278e9
export only the parts of aeson that are used
Rather than hiding things not wanted. This fixes a build warning with
aeson-2.2.3 which no longer has a json function.
2024-09-25 14:41:23 -04:00

122 lines
3.5 KiB
Haskell

{- GHC File system encoding support for Aeson.
-
- Import instead of Data.Aeson
-
- Copyright 2018-2023 Joey Hess <id@joeyh.name>
-
- License: BSD-2-clause
-}
{-# LANGUAGE FlexibleInstances, TypeSynonymInstances, CPP #-}
module Utility.Aeson (
module X,
ToJSON'(..),
encode,
packString,
packByteString,
textKey,
) where
import Data.Aeson as X (decode, eitherDecode, parseJSON, FromJSON, Object, object, Value(..), (.=), (.:), (.:?))
import Data.Aeson hiding (encode)
import qualified Data.Aeson
#if MIN_VERSION_aeson(2,0,0)
import qualified Data.Aeson.Key as AK
#endif
import qualified Data.Text as T
import qualified Data.Text.Encoding as T
import qualified Data.ByteString.Lazy as L
import qualified Data.ByteString as S
import qualified Data.Set
import qualified Data.Map
import qualified Data.Vector
import Prelude
import Utility.FileSystemEncoding
-- | Use this instead of Data.Aeson.encode to make sure that the
-- below String instance is used.
encode :: ToJSON' a => a -> L.ByteString
encode = Data.Aeson.encode . toJSON'
-- | Aeson has an unfortunate ToJSON instance for Char and [Char]
-- which does not support Strings containing UTF8 characters
-- encoded using the filesystem encoding when run in a non-utf8 locale.
--
-- Since we can't replace that with a instance that does the right
-- thing, instead here's a new class that handles String right.
class ToJSON' a where
toJSON' :: a -> Value
instance ToJSON' T.Text where
toJSON' = toJSON
instance ToJSON' String where
toJSON' = toJSON . packString
-- | Aeson does not have a ToJSON instance for ByteString;
-- this one assumes that the ByteString contains text, and will
-- have the same effect as toJSON' . decodeBS, but with a more efficient
-- implementation.
instance ToJSON' S.ByteString where
toJSON' = toJSON . packByteString
-- | Pack a String to Text, correctly handling the filesystem encoding.
--
-- Use this instead of Data.Text.pack.
--
-- Note that if the string contains invalid UTF8 characters not using
-- the FileSystemEncoding, this is the same as Data.Text.pack.
packString :: String -> T.Text
packString s = case T.decodeUtf8' (encodeBS s) of
Right t -> t
Left _ -> T.pack s
#if MIN_VERSION_aeson(2,0,0)
textKey :: T.Text -> AK.Key
textKey = AK.fromText
#else
textKey :: T.Text -> T.Text
textKey = id
#endif
-- | The same as packString . decodeBS, but more efficient in the usual
-- case.
packByteString :: S.ByteString -> T.Text
packByteString b = case T.decodeUtf8' b of
Right t -> t
Left _ -> T.pack (decodeBS b)
-- | An instance for lists cannot be included as it would overlap with
-- the String instance. Instead, you can use a Vector.
instance ToJSON' s => ToJSON' (Data.Vector.Vector s) where
toJSON' = toJSON . map toJSON' . Data.Vector.toList
-- Aeson generates the same JSON for a Set as for a list.
instance ToJSON' s => ToJSON' (Data.Set.Set s) where
toJSON' = toJSON . map toJSON' . Data.Set.toList
instance (ToJSON' v) => ToJSON' (Data.Map.Map T.Text v) where
toJSON' m = object $ map go (Data.Map.toList m)
where
go (k, v) = (textKey k, toJSON' v)
instance (ToJSON' a, ToJSON a) => ToJSON' (Maybe a) where
toJSON' (Just a) = toJSON (Just (toJSON' a))
toJSON' v@Nothing = toJSON v
instance (ToJSON' a, ToJSON a, ToJSON' b, ToJSON b) => ToJSON' (a, b) where
toJSON' (a, b) = toJSON ((toJSON' a, toJSON' b))
instance ToJSON' Bool where
toJSON' = toJSON
instance ToJSON' Integer where
toJSON' = toJSON
instance ToJSON' Object where
toJSON' = toJSON
instance ToJSON' Value where
toJSON' = toJSON