add regression test for #1059

Author: julmb

aeson.cabal

@@ -175,6 +175,7 @@ test-suite aeson-tests
     Regression.Issue571
     Regression.Issue687
     Regression.Issue967
+    Regression.Issue1059
     RFC8785
     SerializationFormatSpec
     Types

tests/Regression/Issue1059.hs

@@ -0,0 +1,38 @@
+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE DeriveFunctor #-}
+{-# LANGUAGE DeriveGeneric #-}
+{-# LANGUAGE StandaloneDeriving #-}
+{-# LANGUAGE UndecidableInstances #-}
+
+module Regression.Issue1059 (issue1059) where
+
+import GHC.Generics
+import Data.Aeson
+import Test.Tasty
+import Test.Tasty.HUnit
+
+data Item f a = Item { rec0 :: Int, par1 :: a, rec1 :: f a, comp1 :: f (f a) } deriving (Functor, Generic1)
+
+deriving instance (Eq a, Eq (f a), Eq (f (f a))) => Eq (Item f a)
+deriving instance (Show a, Show (f a), Show (f (f a))) => Show (Item f a)
+
+instance (Functor f, FromJSON1 f) => FromJSON1 (Item f) where
+    liftParseJSON = genericLiftParseJSON $ defaultOptions { allowOmittedFields = True }
+instance (Functor f, ToJSON1 f) => ToJSON1 (Item f) where
+    liftToJSON = genericLiftToJSON $ defaultOptions { omitNothingFields = True }
+instance (Functor f, FromJSON1 f, FromJSON a) => FromJSON (Item f a) where parseJSON = parseJSON1
+instance (Functor f, ToJSON1 f, ToJSON a) => ToJSON (Item f a) where toJSON = toJSON1
+
+data Test a = Test { a :: Item [] (Maybe a), b :: Item Maybe a } deriving (Eq, Show, Generic1)
+
+instance FromJSON1 Test where liftParseJSON = genericLiftParseJSON defaultOptions
+instance ToJSON1 Test where liftToJSON = genericLiftToJSON defaultOptions
+instance FromJSON a => FromJSON (Test a) where parseJSON = parseJSON1
+instance ToJSON a => ToJSON (Test a) where toJSON = toJSON1
+
+issue1059 :: TestTree
+issue1059 = testCase "issue1059" $ do
+    let value = Test (Item 0 Nothing [] []) (Item 0 1 Nothing Nothing) :: Test Int
+    let code = "{\"a\":{\"comp1\":[],\"rec0\":0,\"rec1\":[]},\"b\":{\"par1\":1,\"rec0\":0}}"
+    encode value @?= code
+    decode code @?= Just value

tests/UnitTests.hs

@@ -64,6 +64,7 @@ import Regression.Issue351
 import Regression.Issue571
 import Regression.Issue687
 import Regression.Issue967
+import Regression.Issue1059
 import UnitTests.OmitNothingFieldsNote
 import UnitTests.FromJSONKey
 import UnitTests.Hashable
@@ -568,6 +569,7 @@ tests = testGroup "unit" [
   , issue571
   , issue687
   , issue967
+  , issue1059
   , keyMapInsertWithTests
   , omitNothingFieldsNoteTests
   , noThunksTests