aeson-gadt-th: Derivation of Aeson instances for GADTs

[ bsd3, json, library ] [ Propose Tags ]

Template Haskell for generating ToJSON and FromJSON instances for GADTs. See for examples.

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Versions [RSS] [faq],,,,,,,, 0.2.2, 0.2.3, 0.2.4,, (info)
Dependencies aeson, aeson-gadt-th, base (>=4.11 && <4.13), dependent-sum (<, markdown-unlit, template-haskell, transformers [details]
License BSD-3-Clause
Copyright 2019 Obsidian Systems LLC
Author Obsidian Systems LLC
Revised Revision 2 made by abrar at 2020-10-05T17:56:30Z
Category JSON
Source repo head: git clone git://
Uploaded by abrar at 2019-01-25T22:35:24Z
Distributions NixOS:
Executables readme
Downloads 3988 total (47 in the last 30 days)
Rating 2.0 (votes: 1) [estimated by Bayesian average]
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Status Hackage Matrix CI
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Provides Template Haskell expressions for deriving ToJSON and FromJSON instances for GADTs.

Example Usage:

{-# LANGUAGE KindSignatures #-}
{-# LANGUAGE TemplateHaskell #-}
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE MultiParamTypeClasses #-}

import Data.Aeson
import Data.Aeson.GADT.TH

data A :: * -> * where
  A_a :: A a
  A_b :: Int -> A ()

data B c :: * -> * where
  B_a :: c -> A a -> B c a
  B_x :: B c x

deriveJSONGADT ''A
deriveJSONGADT ''B

main :: IO ()
main = return ()


encode A_a
> "[\"A_a\",[]]"


When decoding a JSON-encoded GADT, the result will be wrapped using Data.Some.This.

case (decode $ encode A_a) :: Maybe (Some A) of
  Nothing -> error "Couldn't decode
  Just (This A_a) -> putStrLn "it worked"
  Just (This A_b) -> putStrLn "wat"
> it worked