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Poscat
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Implement generic encoding and decoding for TaggingFlatObject
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‎Data/Aeson/Types/FromJSON.hs

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Original file line numberDiff line numberDiff line change
@@ -10,6 +10,7 @@
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{-# LANGUAGE PolyKinds #-}
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{-# LANGUAGE RecordWildCards #-}
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{-# LANGUAGE ScopedTypeVariables #-}
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{-# LANGUAGE TypeApplications #-}
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{-# LANGUAGE TypeOperators #-}
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{-# LANGUAGE TupleSections #-}
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{-# LANGUAGE UndecidableInstances #-}
@@ -158,6 +159,8 @@ import qualified Data.Primitive.Types as PM
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import qualified Data.Primitive.PrimArray as PM
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import Data.Coerce (Coercible, coerce)
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import GHC.TypeNats
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import Data.Kind (Type)
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parseIndexedJSON :: (Value -> Parser a) -> Int -> Value -> Parser a
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parseIndexedJSON p idx value = p value <?> Index idx
@@ -1010,6 +1013,7 @@ instance ( ConstructorNames f
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, FromPair arity f
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, FromTaggedObject arity f
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, FromUntaggedValue arity f
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, FromTaggedFlatObject arity f
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) => ParseSum arity f True where
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parseSum p@(tname :* opts :* _)
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| allNullaryToStringTag opts = Tagged . parseAllNullarySum tname opts
@@ -1019,6 +1023,7 @@ instance ( ConstructorNames f
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, FromPair arity f
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, FromTaggedObject arity f
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, FromUntaggedValue arity f
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, FromTaggedFlatObject arity f
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) => ParseSum arity f False where
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parseSum p = Tagged . parseNonAllNullarySum p
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@@ -1101,6 +1106,7 @@ parseNonAllNullarySum :: forall f c arity.
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( FromPair arity f
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, FromTaggedObject arity f
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, FromUntaggedValue arity f
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, FromTaggedFlatObject arity f
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, ConstructorNames f
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) => TypeName :* Options :* FromArgs arity c
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-> Value -> Parser (f c)
@@ -1118,6 +1124,17 @@ parseNonAllNullarySum p@(tname :* opts :* _) =
11181124
", but found tag " ++ show tag
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cnames_ = unTagged2 (constructorTags (constructorTagModifier opts) :: Tagged2 f [String])
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TaggedFlatObject{..} ->
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withObject tname $ \obj -> do
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let tagKey = pack tagFieldName
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badTag tag = failWith_ $ \cnames ->
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"expected tag field to be one of " ++ show cnames ++
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", but found tag " ++ show tag
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cnames_ = unTagged2 (constructorTags (constructorTagModifier opts) :: Tagged2 f [String])
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tag <- contextType tname . contextTag tagKey cnames_ $ obj .: tagKey
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fromMaybe (badTag tag <?> Key tagKey) $
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parseTaggedFlatObject (tag :* p) obj
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ObjectWithSingleField ->
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withObject tname $ \obj -> case H.toList obj of
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[(tag, v)] -> maybe (badTag tag) (<?> Key tag) $
@@ -1401,6 +1418,63 @@ instance ( Constructor c
14011418

14021419
--------------------------------------------------------------------------------
14031420

1421+
class FromTaggedFlatObject arity f where
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parseTaggedFlatObject :: Text :* TypeName :* Options :* FromArgs arity a
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-> Object
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-> Maybe (Parser (f a))
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instance ( FromTaggedFlatObject arity f
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, FromTaggedFlatObject arity g
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) => FromTaggedFlatObject arity (f :+: g) where
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parseTaggedFlatObject p obj =
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(fmap L1 <$> parseTaggedFlatObject p obj) <|>
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(fmap R1 <$> parseTaggedFlatObject p obj)
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1433+
instance ( IsRecord f isRecord
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, FromTaggedFlatObject' arity f isRecord
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, Constructor c
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) => FromTaggedFlatObject arity (C1 c f) where
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parseTaggedFlatObject (tag :* p@(_ :* opts :* _)) obj
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| tag == tag' = Just $ fmap M1 $ (unTagged @Type @isRecord) $ parseTaggedFlatObject' (cname :* p) obj
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| otherwise = Nothing
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where
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tag' = pack $ constructorTagModifier opts cname
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cname = conName (undefined :: M1 i c a p)
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1444+
class FromTaggedFlatObject' arity f isRecord where
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parseTaggedFlatObject' :: ConName :* TypeName :* Options :* FromArgs arity a
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-> Object
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-> Tagged isRecord (Parser (f a))
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1449+
instance (RecordFromJSON arity f, FieldNames f) => FromTaggedFlatObject' arity f True where
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parseTaggedFlatObject' p = Tagged . recordParseJSON (True :* p)
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1452+
instance FromTaggedFlatObject' arity U1 False where
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parseTaggedFlatObject' _ _ = Tagged (pure U1)
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1455+
instance OVERLAPPABLE_ (PositionFromObject 1 arity f) => FromTaggedFlatObject' arity f False where
1456+
parseTaggedFlatObject' (_ :* p) obj = Tagged (positionFromObject (Proxy @1) p obj)
1457+
1458+
class KnownNat n => PositionFromObject n arity f where
1459+
positionFromObject :: Proxy n
1460+
-> TypeName :* Options :* FromArgs arity a
1461+
-> Object
1462+
-> Parser (f a)
1463+
1464+
instance (KnownNat n, GFromJSON arity a) => PositionFromObject n arity (S1 m a) where
1465+
positionFromObject _ (_ :* opts :* fargs) obj =
1466+
explicitParseField (gParseJSON opts fargs) obj $ pack $ show $ natVal $ Proxy @n
1467+
1468+
instance ( PositionFromObject n arity f
1469+
, PositionFromObject (n+1) arity g
1470+
) => PositionFromObject n arity (f :*: g) where
1471+
positionFromObject _ p obj =
1472+
(:*:)
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<$> positionFromObject (Proxy @n) p obj
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<*> positionFromObject (Proxy @(n+1)) p obj
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1476+
--------------------------------------------------------------------------------
1477+
14041478
class FromUntaggedValue arity f where
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parseUntaggedValue :: TypeName :* Options :* FromArgs arity a
14061480
-> Value

‎Data/Aeson/Types/Internal.hs

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Original file line numberDiff line numberDiff line change
@@ -682,6 +682,8 @@ data SumEncoding =
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-- by the encoded value of that field! If the constructor is not a
683683
-- record the encoded constructor contents will be stored under
684684
-- the 'contentsFieldName' field.
685+
| TaggedFlatObject { tagFieldName :: String }
686+
-- ^ A constructor will be encoded to an object with a field
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| UntaggedValue
686688
-- ^ Constructor names won't be encoded. Instead only the contents of the
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-- constructor will be encoded as if the type had a single constructor. JSON

‎Data/Aeson/Types/ToJSON.hs

Lines changed: 65 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1,3 +1,4 @@
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{-# LANGUAGE DataKinds #-}
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{-# LANGUAGE CPP #-}
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{-# LANGUAGE DefaultSignatures #-}
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{-# LANGUAGE EmptyDataDecls #-}
@@ -141,6 +142,7 @@ import qualified Data.Primitive.Array as PM
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import qualified Data.Primitive.SmallArray as PM
142143
import qualified Data.Primitive.Types as PM
143144
import qualified Data.Primitive.PrimArray as PM
145+
import GHC.TypeNats
144146

145147
toJSONPair :: (a -> Value) -> (b -> Value) -> (a, b) -> Value
146148
toJSONPair a b = liftToJSON2 a (listValue a) b (listValue b)
@@ -851,6 +853,7 @@ class SumToJSON enc arity f allNullary where
851853
instance ( GetConName f
852854
, FromString enc
853855
, TaggedObject enc arity f
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, TaggedFlatObject enc arity f
854857
, SumToJSON' ObjectWithSingleField enc arity f
855858
, SumToJSON' TwoElemArray enc arity f
856859
, SumToJSON' UntaggedValue enc arity f
@@ -862,6 +865,7 @@ instance ( GetConName f
862865
| otherwise = Tagged . nonAllNullarySumToJSON opts targs
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864867
instance ( TaggedObject enc arity f
868+
, TaggedFlatObject enc arity f
865869
, SumToJSON' ObjectWithSingleField enc arity f
866870
, SumToJSON' TwoElemArray enc arity f
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, SumToJSON' UntaggedValue enc arity f
@@ -870,6 +874,7 @@ instance ( TaggedObject enc arity f
870874
sumToJSON opts targs = Tagged . nonAllNullarySumToJSON opts targs
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872876
nonAllNullarySumToJSON :: ( TaggedObject enc arity f
877+
, TaggedFlatObject enc arity f
873878
, SumToJSON' ObjectWithSingleField enc arity f
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, SumToJSON' TwoElemArray enc arity f
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, SumToJSON' UntaggedValue enc arity f
@@ -881,6 +886,9 @@ nonAllNullarySumToJSON opts targs =
881886
TaggedObject{..} ->
882887
taggedObject opts targs tagFieldName contentsFieldName
883888

889+
TaggedFlatObject{..} ->
890+
taggedFlatObject opts targs tagFieldName
891+
884892
ObjectWithSingleField ->
885893
(unTagged :: Tagged ObjectWithSingleField enc -> enc)
886894
. sumToJSON' opts targs
@@ -906,6 +914,63 @@ instance FromString Value where
906914

907915
--------------------------------------------------------------------------------
908916

917+
class TaggedFlatObject enc arity f where
918+
taggedFlatObject :: Options -> ToArgs enc arity a
919+
-> String -> f a -> enc
920+
921+
instance (TaggedFlatObject enc arity a
922+
, TaggedFlatObject enc arity b
923+
) => TaggedFlatObject enc arity (a :+: b)
924+
where
925+
taggedFlatObject opts targs tagFieldName (L1 x) =
926+
taggedFlatObject opts targs tagFieldName x
927+
taggedFlatObject opts targs tagFieldName (R1 x) =
928+
taggedFlatObject opts targs tagFieldName x
929+
930+
instance ( IsRecord a isRecord
931+
, TaggedFlatObject' enc pairs arity a isRecord
932+
, KeyValuePair enc pairs
933+
, FromString enc
934+
, Constructor c
935+
, FromPairs enc pairs
936+
) => TaggedFlatObject enc arity (C1 c a) where
937+
taggedFlatObject opts targs tagFieldName (M1 a) =
938+
fromPairs (tag `mappend` contents)
939+
where
940+
tag :: pairs
941+
tag = tagFieldName `pair`
942+
(fromString (constructorTagModifier opts (conName (undefined :: t c a p)))
943+
:: enc)
944+
contents :: pairs
945+
contents = (unTagged :: Tagged isRecord pairs -> pairs) $ taggedFlatObject' opts targs a
946+
947+
class TaggedFlatObject' enc pairs arity f isRecord where
948+
taggedFlatObject' :: Options -> ToArgs enc arity a
949+
-> f a -> Tagged isRecord pairs
950+
951+
instance RecordToPairs pairs enc arity f => TaggedFlatObject' pairs enc arity f True where
952+
taggedFlatObject' opts targs = Tagged . recordToPairs opts targs
953+
954+
instance Monoid pairs => TaggedFlatObject' enc pairs arity U1 False where
955+
taggedFlatObject' _ _ _ = Tagged mempty
956+
957+
instance OVERLAPPABLE_ (PositionToPairs 1 pairs enc arity f) => TaggedFlatObject' enc pairs arity f False where
958+
taggedFlatObject' opts targs a = Tagged $ positionToPairs (Proxy :: Proxy 1) opts targs a
959+
960+
class KnownNat n => PositionToPairs n pairs enc arity f where
961+
positionToPairs :: Proxy n -> Options -> ToArgs enc arity a -> f a -> pairs
962+
963+
instance (KeyValuePair enc pairs, GToJSON' enc arity a, KnownNat n) => PositionToPairs n pairs enc arity (S1 m a) where
964+
positionToPairs p opts targs (M1 a) =
965+
show (natVal p) `pair` gToJSON opts targs a
966+
967+
instance (Semigroup pairs, PositionToPairs n pairs enc arity f, PositionToPairs (n+1) pairs enc arity g) => PositionToPairs n pairs enc arity (f :*: g) where
968+
positionToPairs _ opts targs (f :*: g) =
969+
positionToPairs (Proxy :: Proxy n) opts targs f
970+
<> positionToPairs (Proxy :: Proxy (n+1)) opts targs g
971+
972+
--------------------------------------------------------------------------------
973+
909974
class TaggedObject enc arity f where
910975
taggedObject :: Options -> ToArgs enc arity a
911976
-> String -> String

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