eb3e4d3 · typeable/aeson

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Start working on release notes and expanded examples.

eb3e4d3Bryan O'Sullivan15 years ago

Data/Aeson/Generic.hs+27−4

compare with master

unifiedsplit

@@ -16,14 +16,18 @@

17module Data.Aeson.Generic

18 (

19+ -- * Decoding and encoding

20+ decode

21+ , encode

22+ -- * Lower-level conversion functions

19− fromJSON

23+ , fromJSON

20 , toJSON

24 , toJSON

21 ) where

25 ) where

23import Control.Applicative ((<$>))

27import Control.Applicative ((<$>))

24import Control.Arrow (first)

28import Control.Arrow (first)

25import Control.Monad.State.Strict

29import Control.Monad.State.Strict

26−import Data.Aeson.Functions

30+import Data.Aeson.Functions hiding (decode)

27import Data.Aeson.Types hiding (FromJSON(..), ToJSON(..), fromJSON)

31import Data.Aeson.Types hiding (FromJSON(..), ToJSON(..), fromJSON)

28import Data.Attoparsec.Number (Number)

32import Data.Attoparsec.Number (Number)

29import Data.Generics

33import Data.Generics

@@ -35,7 +39,11 @@ import Data.Text (Text, pack, unpack)

35import Data.Text.Encoding (encodeUtf8)

39import Data.Text.Encoding (encodeUtf8)

36import Data.Time.Clock (UTCTime)

40import Data.Time.Clock (UTCTime)

37import Data.Word (Word, Word8, Word16, Word32, Word64)

41import Data.Word (Word, Word8, Word16, Word32, Word64)

42+import Data.Aeson.Parser (json)

43+import qualified Data.Aeson.Encode as E

44+import qualified Data.Aeson.Functions as F

38import qualified Data.Aeson.Types as T

45import qualified Data.Aeson.Types as T

46+import qualified Data.Attoparsec.Lazy as L

39import qualified Data.ByteString as B

47import qualified Data.ByteString as B

40import qualified Data.ByteString.Lazy as L

48import qualified Data.ByteString.Lazy as L

41import qualified Data.HashMap.Strict as H

49import qualified Data.HashMap.Strict as H

@@ -46,6 +54,21 @@ import qualified Data.Text.Lazy as LT

46import qualified Data.Traversable as T

54import qualified Data.Traversable as T

47import qualified Data.Vector as V

55import qualified Data.Vector as V

57+-- | Efficiently serialize a JSON value as a lazy 'L.ByteString'.

58+encode :: (Data a) => a -> L.ByteString

59+encode = E.encode . toJSON

60+{-# INLINE encode #-}

61+

62+-- | Efficiently deserialize a JSON value from a lazy 'L.ByteString'.

63+-- If this fails due to incomplete or invalid input, 'Nothing' is

64+-- returned.

65+decode :: (Data a) => L.ByteString -> Maybe a

66+decode s = case L.parse json s of

67+ L.Done _ v -> case fromJSON v of

68+ Success a -> Just a

69+ _ -> Nothing

70+ _ -> Nothing

71+

49type T a = a -> Value

72type T a = a -> Value

51toJSON :: (Data a) => a -> Value

74toJSON :: (Data a) => a -> Value

@@ -93,7 +116,7 @@ toJSON = toJSON_generic

93 | tyrep == typeOf DT.empty = remap id

116 | tyrep == typeOf DT.empty = remap id

94 | tyrep == typeOf LT.empty = remap LT.toStrict

117 | tyrep == typeOf LT.empty = remap LT.toStrict

95 | tyrep == typeOf "" = remap pack

118 | tyrep == typeOf "" = remap pack

96− | tyrep == typeOf B.empty = remap decode

119+ | tyrep == typeOf B.empty = remap F.decode

97 | tyrep == typeOf L.empty = remap strict

120 | tyrep == typeOf L.empty = remap strict

98 | otherwise = modError "toJSON" $

121 | otherwise = modError "toJSON" $

99 "cannot convert map keyed by type " ++ show tyrep

122 "cannot convert map keyed by type " ++ show tyrep

@@ -104,7 +127,7 @@ toJSON = toJSON_generic

104 | tyrep == typeOf DT.empty = remap id

127 | tyrep == typeOf DT.empty = remap id

105 | tyrep == typeOf LT.empty = remap LT.toStrict

128 | tyrep == typeOf LT.empty = remap LT.toStrict

106 | tyrep == typeOf "" = remap pack

129 | tyrep == typeOf "" = remap pack

107− | tyrep == typeOf B.empty = remap decode

130+ | tyrep == typeOf B.empty = remap F.decode

108 | tyrep == typeOf L.empty = remap strict

131 | tyrep == typeOf L.empty = remap strict

109 | otherwise = modError "toJSON" $

132 | otherwise = modError "toJSON" $

110 "cannot convert map keyed by type " ++ show tyrep

133 "cannot convert map keyed by type " ++ show tyrep

aeson.cabal+12−7

@@ -3,15 +3,16 @@ version: 0.4.0.0

3license: BSD3

4license-file: LICENSE

5category: Text, Web, JSON

7author: Bryan O'Sullivan <bos@serpentine.com>

8author: Bryan O'Sullivan <bos@serpentine.com>

8maintainer: Bryan O'Sullivan <bos@serpentine.com>

9maintainer: Bryan O'Sullivan <bos@serpentine.com>

9stability: experimental

10stability: experimental

10−tested-with: GHC == 6.12.3

11+tested-with: GHC == 6.12.3, GHC == 7.0.4, GHC == 7.2.2

11synopsis: Fast JSON parsing and encoding

12synopsis: Fast JSON parsing and encoding

12cabal-version: >= 1.8

13cabal-version: >= 1.8

13−homepage: http://github.com/bos/aeson

14+homepage: https://github.com/bos/aeson

14−bug-reports: http://github.com/bos/aeson/issues

15+bug-reports: https://github.com/bos/aeson/issues

15build-type: Simple

16build-type: Simple

16description:

17description:

17 A JSON parsing and encoding library optimized for ease of use

18 A JSON parsing and encoding library optimized for ease of use

@@ -20,6 +21,9 @@ description:

20 To get started, see the documentation for the @Data.Aeson@ module

21 To get started, see the documentation for the @Data.Aeson@ module

21 below.

22 below.

22 .

23 .

24+ For release notes, see

25+ <https://github.com/bos/aeson/blob/master/release-notes.markdown>

26+ .

23 /Note/: if you use GHCi or Template Haskell, please see the

27 /Note/: if you use GHCi or Template Haskell, please see the

24 @README@ file for important details about building this package,

28 @README@ file for important details about building this package,

25 and other packages that depend on it:

29 and other packages that depend on it:

@@ -80,6 +84,7 @@ description:

81extra-source-files:

85extra-source-files:

82 README.markdown

86 README.markdown

87+ release-notes.markdown

83 benchmarks/AesonEncode.hs

88 benchmarks/AesonEncode.hs

84 benchmarks/AesonParse.hs

89 benchmarks/AesonParse.hs

85 benchmarks/JsonParse.hs

90 benchmarks/JsonParse.hs

@@ -98,7 +103,7 @@ extra-source-files:

98 benchmarks/json-data/twitter50.json

103 benchmarks/json-data/twitter50.json

99 benchmarks/json-data/twitter100.json

104 benchmarks/json-data/twitter100.json

100 tests/Properties.hs

105 tests/Properties.hs

101− examples/Demo.hs

106+ examples/*.hs

102

107

103flag developer

108flag developer

104 description: operate in developer mode

109 description: operate in developer mode

@@ -170,8 +175,8 @@ test-suite tests

170

175

171source-repository head

176source-repository head

172 type: git

177 type: git

173− location: http://github.com/bos/aeson

178+ location: git://github.com/bos/aeson.git

174

179

175source-repository head

180source-repository head

176 type: mercurial

181 type: mercurial

177− location: http://bitbucket.org/bos/aeson

182+ location: https://bitbucket.org/bos/aeson

examples/Generic.hsnew file+38

@@ -0,0 +1,38 @@

1+-- This example is basically the same as in Simplest.hs, only it uses

2+-- GHC's builtin generics instead of explicit instances of ToJSON and

3+-- FromJSON.

5+-- This example only works with GHC 7.2 or newer, as it uses the

6+-- datatype-generic programming machinery introduced in 7.2.

8+-- We enable the DeriveGeneric language extension so that GHC can

9+-- automatically derive the Generic class for us.

10+

11+{-# LANGUAGE DeriveGeneric #-}

12+

13+{-# LANGUAGE OverloadedStrings #-}

14+

15+import Data.Aeson (FromJSON, ToJSON, decode, encode)

16+import qualified Data.ByteString.Lazy.Char8 as BL

17+

18+-- To decode or encode a value using the generic machinery, we must

19+-- make the type an instance of the Generic class.

20+

21+import GHC.Generics (Generic)

22+

23+data Coord = Coord { x :: Double, y :: Double }

24+ deriving (Show, Generic)

25+

26+-- While we still have to declare our type as instances of FromJSON

27+-- and ToJSON, we do *not* need to provide bodies for the instances.

28+-- Default versions will be supplied for us.

29+

30+instance FromJSON Coord

31+instance ToJSON Coord

32+

33+main ::IO ()

34+main = do

35+ let req = decode "{\"x\":3.0,\"y\":-1.0}" :: Maybe Coord

36+ print req

37+ let reply = Coord 123.4 20

38+ BL.putStrLn (encode reply)

examples/GenericSYB.hsnew file+30

@@ -0,0 +1,30 @@

1+-- This example is basically the same as in Simplest.hs, only it uses

2+-- SYB generics instead of explicit instances of ToJSON and FromJSON.

4+-- This mechanism is much slower than the newer generics mechanism

5+-- demonstrated in Generic.hs, but it works on versions of GHC older

6+-- than 7.2.

8+-- We enable the DeriveDataTypeable language extension so that GHC can

9+-- automatically derive the Typeable and Data classes for us.

10+

11+{-# LANGUAGE DeriveDataTypeable #-}

12+

13+{-# LANGUAGE OverloadedStrings #-}

14+

15+import Data.Data (Typeable, Data)

16+import Data.Aeson.Generic (decode, encode)

17+import qualified Data.ByteString.Lazy.Char8 as BL

18+

19+-- To decode or encode a value using the generic machinery, we must

20+-- make the type an instance of the Typeable and Data classes.

21+

22+data Coord = Coord { x :: Double, y :: Double }

23+ deriving (Show, Typeable, Data)

24+

25+main ::IO ()

26+main = do

27+ let req = decode "{\"x\":3.0,\"y\":-1.0}" :: Maybe Coord

28+ print req

29+ let reply = Coord 123.4 20

30+ BL.putStrLn (encode reply)

examples/Simplest.hs+19−22

@@ -1,33 +1,30 @@

1{-# LANGUAGE OverloadedStrings #-}

3−import Control.Applicative ((<$>), (<*>))

3+import Control.Applicative ((<$>), (<*>), empty)

4−import Control.Monad (mzero)

5import Data.Aeson

4import Data.Aeson

6−import qualified Data.Aeson.Types as T

5+import qualified Data.ByteString.Lazy.Char8 as BL

7−import Data.Attoparsec (parse, Result(..))

8−import qualified Data.ByteString.Char8 as BS

9−import qualified Data.ByteString.Lazy.Char8 as BSL

11−main ::IO ()

7+data Coord = Coord { x :: Double, y :: Double }

12−main = do

8+ deriving (Show)

13− print $ parseFromString "{\"x\":3.0,\"y\":-1.0}"

14− let reply = Coord 123.4 20

15− putStrLn $ BSL.unpack (encode reply)

17−data Coord = Coord { x :: Double, y :: Double } deriving (Show)

10+-- A ToJSON instance allows us to encode a value as JSON.

19instance ToJSON Coord where

12instance ToJSON Coord where

20− toJSON (Coord xV yV) = object ["x" .= xV, "y" .= yV]

13+ toJSON (Coord xV yV) = object [ "x" .= xV,

14+ "y" .= yV ]

15+

16+-- A FromJSON instance allows us to decode a value from JSON. This

17+-- should match the format used by the ToJSON instance.

22instance FromJSON Coord where

19instance FromJSON Coord where

23 parseJSON (Object v) = Coord <$>

20 parseJSON (Object v) = Coord <$>

24− v .: "x" <*>

21+ v .: "x" <*>

25− v .: "y"

22+ v .: "y"

26− parseJSON _ = mzero

23+ parseJSON _ = empty

28−parseFromString :: String -> Maybe Coord

25+main ::IO ()

29−parseFromString s =

26+main = do

30− let bs = BS.pack s

27+ let req = decode "{\"x\":3.0,\"y\":-1.0}" :: Maybe Coord

31− in case parse json bs of

28+ print req

32− Done _rest res -> T.parseMaybe parseJSON res

29+ let reply = Coord 123.4 20

33− _ -> Nothing

30+ BL.putStrLn (encode reply)

release-notes.markdownnew file+27

@@ -0,0 +1,27 @@

1+# 0.3 to 0.4

3+## Generics support

5+Aeson's support for data-type generic programming makes it possible to

6+use JSON encodings of most data types without writing any boilerplate

7+instances.

9+Thanks to Bas Van Dijk, aeson now supports the two major schemes for

10+doing datatype-generic programming:

11+

12+* the newer mechanism, [built into GHC

13+ itself](http://www.haskell.org/ghc/docs/latest/html/users_guide/generic-programming.html)

14+

15+* the older mechanism, based on SYB (for "scrap your boilerplate")

16+

17+The GHC-based generics are fast and terse: in fact, they're generally

18+comparable in performance to hand-written `ToJSON` and `FromJSON`

19+instances. To see how to use GHC generics, see

20+[`examples/Generic.hs`](https://github.com/bos/aeson/blob/master/examples/Generic.hs).

21+

22+The SYB-based generics support lives in

23+[Data.Aeson.Generic](http://hackage.haskell.org/packages/archive/aeson/0.4.0.0/doc/html/Data-Aeson-Generic.html),

24+and is provided mainly for users of GHC older than 7.2. It's far

25+slower (by about 10x) than the more modern generic mechanism. To see

26+how to use SYB generics, see

27+[`examples/GenericSYB.hs`](https://github.com/bos/aeson/blob/master/examples/GenericSYB.hs).