aeson-gadt-th
Derivation of Aeson instances for GADTs
| LTS Haskell 24.17: | 0.2.5.4 |
| Stackage Nightly 2025-10-31: | 0.2.5.4 |
| Latest on Hackage: | 0.2.5.4 |
Maintained by [email protected]
This version can be pinned in stack with:
aeson-gadt-th-0.2.5.4@sha256:ea7d6f6f5e6ba8ed8550fa669221aac2334db025e80aa1d2d1b6f84f4b931ec1,2039Module documentation for 0.2.5.4
- Data
- Data.Aeson
- Data.Aeson.GADT
- Data.Aeson
Depends on 10 packages(full list with versions):
Used by 2 packages in nightly-2025-10-31(full list with versions):
aeson-gadt-th
Provides Template Haskell expressions for deriving ToJSON and FromJSON instances for GADTs.
Example Usage:
> {-# LANGUAGE GADTs #-}
> {-# LANGUAGE KindSignatures #-}
> {-# LANGUAGE TemplateHaskell #-}
> {-# LANGUAGE FlexibleContexts #-}
> {-# LANGUAGE FlexibleInstances #-}
> {-# LANGUAGE UndecidableInstances #-}
> {-# LANGUAGE MultiParamTypeClasses #-}
> {-# OPTIONS_GHC -ddump-splices #-}
> import Data.Aeson
> import Data.Aeson.GADT.TH
> import Data.Dependent.Map (DMap)
> import Data.Dependent.Sum (DSum)
> import Data.Functor.Identity
> import Data.GADT.Compare
> import Data.GADT.Show.TH
> import Data.Kind (Type)
> import Data.Some (Some(..))
> data A :: Type -> Type where
> A_a :: A a
> A_b :: Int -> A ()
> deriveJSONGADT ''A
> deriveGShow ''A
> data B c :: Type -> Type where
> B_a :: c -> A a -> B c a
> B_x :: B c a
> deriveJSONGADT ''B
> data C t :: Type -> Type where
> C_t :: t -> C t t
> deriveJSONGADT ''C
> data D t x :: Type -> Type where
> D_t :: t -> D t x t
> D_x :: x -> D t x x
> D_i :: Int -> D t x Int
> deriveJSONGADT ''D
> data Auth token a where
> Auth_Login :: String -> String -> Auth token (Either String token)
> deriveJSONGADT ''Auth
> -- Some real-world-ish examples.
> -- | Edit operations for `LabelledGraph`
> data LabelledGraphEdit v vm em :: Type -> Type where
> LabelledGraphEdit_ClearAll :: LabelledGraphEdit v vm em ()
> LabelledGraphEdit_AddVertex :: vm -> LabelledGraphEdit v vm em v
> LabelledGraphEdit_AddEdge :: v -> v -> em -> LabelledGraphEdit v vm em ()
> LabelledGraphEdit_SetVertexProperties :: v -> vm -> LabelledGraphEdit v vm em ()
> LabelledGraphEdit_SetEdgeProperties :: v -> v -> em -> LabelledGraphEdit v vm em ()
> -- | PropertyGraphEdit operatios for `PropertyGraph`
> data PropertyGraphEdit v vp ep r where
> PropertyGraphEdit_ClearAll :: PropertyGraphEdit v vp ep ()
> PropertyGraphEdit_AddVertex :: (DMap vp Identity) -> PropertyGraphEdit v vp ep v
> PropertyGraphEdit_AddEdge :: v -> v -> (DMap ep Identity) -> PropertyGraphEdit v vp ep ()
> PropertyGraphEdit_SetVertexProperty :: GCompare vp => v -> DSum vp Identity -> PropertyGraphEdit v vp ep ()
> PropertyGraphEdit_SetEdgeProperty :: GCompare ep => v -> v -> DSum ep Identity -> PropertyGraphEdit v vp ep ()
> -- | View operations for `LabelledGraph`
> data LabelledGraphView v vm em :: Type -> Type where
> LabelledGraphView_All :: LabelledGraphView v vm em ()
> LabelledGraphView_GetVertexProperties :: v -> LabelledGraphView v vm em vm
> LabelledGraphView_GetEdgeProperties :: v -> v -> LabelledGraphView v vm em em
> deriveJSONGADT ''LabelledGraphEdit
> deriveJSONGADT ''PropertyGraphEdit
> deriveJSONGADT ''LabelledGraphView
> main :: IO ()
> main = do
> putStrLn $ unlines
> [ "Encoding of A_a:"
> , show $ encode A_a
> , "Decoding of encoded A_a:"
> , show (decode $ encode A_a :: Maybe (Some A))
> ]
> putStrLn $ unlines
> [ "Encoding of (A_b 1):"
> , show $ encode (A_b 1)
> , "Decoding of encoded (A_b 1):"
> , show (decode $ encode (A_b 1) :: Maybe (Some A))
> ]
> putStrLn $ unlines
> [ "Encoding of (B_a 'a' (A_b 1)):"
> , show $ encode (B_a 'a' (A_b 1))
> , "Decoding of encoded (B_a 'a' (A_b 1)):"
> , case (decode $ encode (B_a 'a' (A_b 1)) :: Maybe (Some (B Char))) of
> Just (Some (B_a 'a' (A_b 1))) -> "Succeeded"
> _-> "Failed"
> ]
