JSON.hs

{-# LANGUAGE DataKinds             #-}
{-# LANGUAGE DeriveGeneric         #-}
{-# LANGUAGE FlexibleContexts      #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE TemplateHaskell       #-}
{-# LANGUAGE TypeFamilies          #-}

module Types.JSON where

import           Data.Aeson
import           Data.Aeson.TH
import           Data.Aeson.Types


instance (ToJSON a, ToJSONKey a) => ToJSONKey (Maybe a) where
  toJSONKey = genericToJSONKey defaultJSONKeyOptions

instance (FromJSON a, FromJSONKey a) => FromJSONKey (Maybe a) where
  fromJSONKey = genericFromJSONKey defaultJSONKeyOptions


{-
lib/Types/JSON.hs:62:17: error:
    • Could not deduce (aeson-1.4.6.0:Data.Aeson.Types.FromJSON.SumFromString
                          (GHC.Generics.M1
                             GHC.Generics.C
                             ('GHC.Generics.MetaCons "Just" 'GHC.Generics.PrefixI 'False)
                             (GHC.Generics.S1
                                ('GHC.Generics.MetaSel
                                   'Nothing
                                   'GHC.Generics.NoSourceUnpackedness
                                   'GHC.Generics.NoSourceStrictness
                                   'GHC.Generics.DecidedLazy)
                                (GHC.Generics.Rec0 a))))
        arising from a use of ‘genericFromJSONKey’
      from the context: (FromJSON a, FromJSONKey a)
        bound by the instance declaration
        at lib/Types/JSON.hs:61:10-61
    • In the expression: genericFromJSONKey defaultJSONKeyOptions
      In an equation for ‘fromJSONKey’:
          fromJSONKey = genericFromJSONKey defaultJSONKeyOptions
      In the instance declaration for ‘FromJSONKey (Maybe a)’
   |
62 |   fromJSONKey = genericFromJSONKey defaultJSONKeyOptions
   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-}