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Lossless Maybe encoding/decoding #23

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Merged
merged 1 commit into from
Apr 7, 2017
Merged

Lossless Maybe encoding/decoding #23

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15 changes: 12 additions & 3 deletions src/Data/Argonaut/Decode/Class.purs
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Original file line number Diff line number Diff line change
Expand Up @@ -68,9 +68,18 @@ gDecodeJson' signature json = case signature of
mFail msg = maybe (Left msg) Right

instance decodeJsonMaybe :: DecodeJson a => DecodeJson (Maybe a) where
decodeJson j
| isNull j = pure Nothing
| otherwise = Just <$> decodeJson j
decodeJson j =
case decode j of
Right x -> Right x
Left x -> backwardsCompat
where
decode =
decodeJObject >=> lookupJust >=> decodeJson
lookupJust =
maybe (Left "Missing property 'just'") Right <<< SM.lookup "just"
backwardsCompat
| isNull j = pure Nothing
| otherwise = Just <$> decodeJson j

instance decodeJsonTuple :: (DecodeJson a, DecodeJson b) => DecodeJson (Tuple a b) where
decodeJson j = decodeJson j >>= f
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6 changes: 3 additions & 3 deletions src/Data/Argonaut/Encode/Class.purs
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Expand Up @@ -2,7 +2,7 @@ module Data.Argonaut.Encode.Class where

import Prelude

import Data.Argonaut.Core (Json(), jsonNull, fromBoolean, fromNumber, fromString, fromArray, fromObject)
import Data.Argonaut.Core (Json(), jsonNull, fromBoolean, fromNumber, fromString, fromArray, fromObject, jsonEmptyObject, jsonSingletonObject)
import Data.Either (Either(), either)
import Data.Foldable (foldr)
import Data.Generic (class Generic, GenericSpine(..), toSpine)
Expand Down Expand Up @@ -42,8 +42,8 @@ gEncodeJson' = case _ of
SM.insert field.recLabel (gEncodeJson' $ field.recValue unit)

instance encodeJsonMaybe :: EncodeJson a => EncodeJson (Maybe a) where
encodeJson Nothing = jsonNull
encodeJson (Just a) = encodeJson a
encodeJson Nothing = jsonEmptyObject
encodeJson (Just a) = jsonSingletonObject "just" (encodeJson a)

instance encodeJsonTuple :: (EncodeJson a, EncodeJson b) => EncodeJson (Tuple a b) where
encodeJson (Tuple a b) = encodeJson [encodeJson a, encodeJson b]
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