102d07f · typeable/aeson

git.iko.soy/typeable/aeson

Add Missing Value for non-present values.

If a Maybe a value should only be optionally included in an Object (as opposed to being set as "null"), then use .=? to construct its Pair. This sets the Value to Missing, which causes it to be subsequently excluded from the Object.

commit102d07f7d8365e6eb38a62c6af019a43201296af authorJeremy Fitzhardinge <jeremy@goop.org> dateThu 17 Feb 2011, 17:33 (16 years ago) parent6b40e5d

3 files changed+16−1

compare with master

unifiedsplit

Data/Aeson.hs+1 Data/Aeson/Encode.hs+1 Data/Aeson/Types.hs+14−1

Data/Aeson.hs+1

@@ -24,6 +24,7 @@ module Data.Aeson

2424 , ToJSON(..)

2525 -- * Constructors and accessors

2626 , (.=)

27+ , (.=?)

2728 , (.:)

2829 , (.:?)

2930 , object

Data/Aeson/Encode.hs+1

@@ -29,6 +29,7 @@ import qualified Data.Vector as V

2929-- | Encode a JSON value to a 'Builder'.

3030fromValue :: Value -> Builder

3131fromValue Null = fromByteString "null"

32+fromValue Missing = error "Unexpected Missing"

3233fromValue (Bool b) = fromByteString $ if b then "true" else "false"

3334fromValue (Number n) = fromByteString (B.pack (show n))

3435fromValue (String s) = string s

Data/Aeson/Types.hs+14−1

@@ -30,6 +30,7 @@ module Data.Aeson.Types

3030 , ToJSON(..)

3131 -- * Constructors and accessors

3232 , (.=)

33+ , (.=?)

3334 , (.:)

3435 , (.:?)

3536 , object

@@ -140,6 +141,7 @@ data Value = Object Object

140141 | Number Number

141142 | Bool !Bool

142143 | Null

144+ | Missing

143145 deriving (Eq, Show, Typeable, Data)

144146

145147instance NFData Value where

@@ -149,6 +151,7 @@ instance NFData Value where

149151 rnf (Number n) = case n of I i -> rnf i; D d -> rnf d

150152 rnf (Bool b) = rnf b

151153 rnf Null = ()

154+ rnf Missing = ()

152155

153156-- | The empty array.

154157emptyArray :: Value

@@ -166,6 +169,14 @@ type Pair = (Text, Value)

166169name .= value = (name, toJSON value)

167170{-# INLINE (.=) #-}

168171

172+-- | Construct an optional 'Pair' from a key and a Maybe value. If

173+-- the value is Nothing, then it is omitted altogether from the

174+-- resulting Object.

175+(.=?) :: ToJSON a => Text -> Maybe a -> Pair

176+name .=? Nothing = (name, Missing)

177+name .=? Just value = (name, toJSON value)

178+{-# INLINE (.=?) #-}

179+

169180-- | Convert a value from JSON, failing if the types do not match.

170181fromJSON :: (FromJSON a) => Value -> Result a

171182fromJSON = parse parseJSON

@@ -205,7 +216,9 @@ obj .:? key = case M.lookup key obj of

205216-- | Create a 'Value' from a list of name\/value 'Pair's. If duplicate

206217-- keys arise, earlier keys and their associated values win.

207218object :: [Pair] -> Value

208−object = Object . M.fromList

219+object = Object . M.fromList . filter (notmissing . snd)

220+ where notmissing Missing = False

221+ notmissing _ = True

209222{-# INLINE object #-}

210223

211224-- | A type that can be converted to JSON.