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Diffstat (limited to 'users/glittershark/xanthous/src/Data/Aeson/Generic/DerivingVia.hs')
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diff --git a/users/glittershark/xanthous/src/Data/Aeson/Generic/DerivingVia.hs b/users/glittershark/xanthous/src/Data/Aeson/Generic/DerivingVia.hs new file mode 100644 index 000000000000..34f2a9403892 --- /dev/null +++ b/users/glittershark/xanthous/src/Data/Aeson/Generic/DerivingVia.hs @@ -0,0 +1,167 @@ +{-# LANGUAGE ConstraintKinds, DataKinds, DeriveGeneric, DerivingVia #-} +{-# LANGUAGE ExplicitNamespaces, FlexibleContexts, FlexibleInstances #-} +{-# LANGUAGE GADTs, GeneralizedNewtypeDeriving, MultiParamTypeClasses #-} +{-# LANGUAGE PolyKinds, ScopedTypeVariables, StandaloneDeriving #-} +{-# LANGUAGE TypeApplications, TypeFamilies, TypeInType, TypeOperators #-} +{-# LANGUAGE UndecidableInstances #-} +{-# OPTIONS_GHC -Wall #-} +-- | https://gist.github.com/konn/27c00f784dd883ec2b90eab8bc84a81d +module Data.Aeson.Generic.DerivingVia + ( StrFun(..), Setting(..), SumEncoding'(..), DefaultOptions, WithOptions(..) + , -- Utility type synonyms to save ticks (') before promoted data constructors + type Drop, type CamelTo2, type UserDefined + , type TaggedObj, type UntaggedVal, type ObjWithSingleField, type TwoElemArr + , type FieldLabelModifier + , type ConstructorTagModifier + , type AllNullaryToStringTag + , type OmitNothingFields + , type SumEnc + , type UnwrapUnaryRecords + , type TagSingleConstructors + ) + where + +import Prelude +import Data.Aeson (FromJSON (..), GFromJSON, GToJSON, + ToJSON (..)) +import Data.Aeson (Options (..), Zero, camelTo2, + genericParseJSON) +import Data.Aeson (defaultOptions, genericToJSON) +import qualified Data.Aeson as Aeson +import Data.Kind (Constraint, Type) +import Data.Proxy (Proxy (..)) +import Data.Reflection (Reifies (..)) +import GHC.Generics (Generic, Rep) +import GHC.TypeLits (KnownNat, KnownSymbol, natVal, symbolVal) +import GHC.TypeLits (Nat, Symbol) + +newtype WithOptions options a = WithOptions { runWithOptions :: a } + +data StrFun = Drop Nat + | CamelTo2 Symbol + | forall p. UserDefined p + +type Drop = 'Drop +type CamelTo2 = 'CamelTo2 +type UserDefined = 'UserDefined + +type family Demoted a where + Demoted Symbol = String + Demoted StrFun = String -> String + Demoted [a] = [Demoted a] + Demoted Setting = Options -> Options + Demoted SumEncoding' = Aeson.SumEncoding + Demoted a = a + +data SumEncoding' = TaggedObj {tagFieldName' :: Symbol, contentsFieldName :: Symbol } + | UntaggedVal + | ObjWithSingleField + | TwoElemArr + +type TaggedObj = 'TaggedObj +type UntaggedVal = 'UntaggedVal +type ObjWithSingleField = 'ObjWithSingleField +type TwoElemArr = 'TwoElemArr + +data Setting = FieldLabelModifier [StrFun] + | ConstructorTagModifier [StrFun] + | AllNullaryToStringTag Bool + | OmitNothingFields Bool + | SumEnc SumEncoding' + | UnwrapUnaryRecords Bool + | TagSingleConstructors Bool + +type FieldLabelModifier = 'FieldLabelModifier +type ConstructorTagModifier = 'ConstructorTagModifier +-- | If 'True' the constructors of a datatype, with all nullary constructors, +-- will be encoded to just a string with the constructor tag. If 'False' the +-- encoding will always follow the 'SumEncoding'. +type AllNullaryToStringTag = 'AllNullaryToStringTag +type OmitNothingFields = 'OmitNothingFields +type SumEnc = 'SumEnc +-- | Hide the field name when a record constructor has only one field, like a +-- newtype. +type UnwrapUnaryRecords = 'UnwrapUnaryRecords +-- | Encode types with a single constructor as sums, so that +-- 'AllNullaryToStringTag' and 'SumEncoding' apply. +type TagSingleConstructors = 'TagSingleConstructors + +class Demotable (a :: k) where + demote :: proxy a -> Demoted k + +type family All (p :: Type -> Constraint) (xs :: [k]) :: Constraint where + All p '[] = () + All p (x ': xs) = (p x, All p xs) + +instance Reifies f (String -> String) => Demotable ('UserDefined f) where + demote _ = reflect @f Proxy + +instance KnownSymbol sym => Demotable sym where + demote = symbolVal + +instance (KnownSymbol s, KnownSymbol t) => Demotable ('TaggedObj s t) where + demote _ = Aeson.TaggedObject (symbolVal @s Proxy) (symbolVal @t Proxy) + +instance Demotable 'UntaggedVal where + demote _ = Aeson.UntaggedValue + +instance Demotable 'ObjWithSingleField where + demote _ = Aeson.ObjectWithSingleField + +instance Demotable 'TwoElemArr where + demote _ = Aeson.TwoElemArray + +instance Demotable xs => Demotable ('FieldLabelModifier xs) where + demote _ o = o { fieldLabelModifier = foldr (.) id (demote (Proxy @xs)) } + +instance Demotable xs => Demotable ('ConstructorTagModifier xs) where + demote _ o = o { constructorTagModifier = foldr (.) id (demote (Proxy @xs)) } + +instance Demotable b => Demotable ('AllNullaryToStringTag b) where + demote _ o = o { allNullaryToStringTag = demote (Proxy @b) } + +instance Demotable b => Demotable ('OmitNothingFields b) where + demote _ o = o { omitNothingFields = demote (Proxy @b) } + +instance Demotable b => Demotable ('UnwrapUnaryRecords b) where + demote _ o = o { unwrapUnaryRecords = demote (Proxy @b) } + +instance Demotable b => Demotable ('TagSingleConstructors b) where + demote _ o = o { tagSingleConstructors = demote (Proxy @b) } + +instance Demotable b => Demotable ('SumEnc b) where + demote _ o = o { sumEncoding = demote (Proxy @b) } + +instance Demotable 'True where + demote _ = True + +instance Demotable 'False where + demote _ = False + +instance KnownNat n => Demotable ('Drop n) where + demote _ = drop (fromIntegral $ natVal (Proxy :: Proxy n)) + +instance KnownSymbol sym => Demotable ('CamelTo2 sym) where + demote _ = camelTo2 $ head $ symbolVal @sym Proxy + +instance {-# OVERLAPPING #-} Demotable ('[] :: [k]) where + demote _ = [] + +instance (Demotable (x :: k), Demotable (xs :: [k])) => Demotable (x ': xs) where + demote _ = demote (Proxy @x) : demote (Proxy @xs) + +type DefaultOptions = ('[] :: [Setting]) + +reflectOptions :: forall xs proxy. Demotable (xs :: [Setting]) => proxy xs -> Options +reflectOptions pxy = foldr (.) id (demote pxy) defaultOptions + +instance (Demotable (options :: [Setting])) => Reifies options Options where + reflect = reflectOptions + +instance (Generic a, GToJSON Zero (Rep a), Reifies (options :: k) Options) + => ToJSON (WithOptions options a) where + toJSON = genericToJSON (reflect (Proxy @options)) . runWithOptions + +instance (Generic a, GFromJSON Zero (Rep a), Reifies (options :: k) Options) + => FromJSON (WithOptions options a) where + parseJSON = fmap WithOptions . genericParseJSON (reflect (Proxy @options)) |