Incorrect ENUM decoding

[horus]

GHC: 8.6.4
Stack: Version 2.1.3, Git revision 0fa51b9925decd937e4a993ad90cb686f88fa282 (7739 commits) x86_64 hpack-0.31.2
Built with: lts-13.19
morpheus-graphql commit: b40fd48

Summary of my problem: a simple enum type (possibly) being decoded incorrectly by the resolver. (Maybe it's just me :-)

The following code example could be used to demonstrate it:

-- types & args
newtype TestArgs = TestArgs
    { ttt :: Level } deriving (Generic, Show)

instance GQLType TestArgs where
    type KIND TestArgs = ENUM

data Level = L0 | L1 | L2 | L3
    deriving (Show, Generic)

instance GQLType Level where
    type KIND Level = ENUM

data TestResult = TestResult
    { code :: Text
    , level :: Level
    } deriving (Generic, Show)

instance GQLType TestResult where
    type KIND TestResult = OBJECT

-- query

qTest :: TestArgs -> IORes TestResult
qTest args = resolver $ return $ Right $ TestResult
  { code  = "ok"
  , level = ttt args
  }

-- resolver

rootResolver :: GQLRootResolver IO () () Query () ()
rootResolver = GQLRootResolver
  { queryResolver        = return Query { test = qTest }
  , mutationResolver     = return ()
  , subscriptionResolver = return ()
  }

Tested with Insomnia:

This, however, generated the correct document for /schema.gql:

type Query { 
  test(ttt: Level!): TestResult!
}

enum Level { 
  L0
  L1
  L2
  L3
}

type TestResult { 
  code: String!
  level: Level!
}

For now, I've came up with a workaround:

-- Data/Morpheus/Resolve/Decode.hs
import           Data.Text                                  (unpack)
import           Text.Read                                  (readMaybe)
--
instance (Generic a, EnumRep (Rep a), Read a) => Decode a ENUM where
  __decode _ (Enum value) = maybe err pure $ readMaybe (unpack value)
    where err = internalArgumentError ("cannot convert to enum: " <> value)
  __decode _ isType       = internalTypeMismatch "Enum" isType

...which seemed to behave correctly. But it would require every ENUM to be an instance of Read, thus I think this is far from ideal.

Would you please help me identify the cause? And thank you for your hard work making morpheus-graphql available!

P./S.

I know there's Data.Morpheus.Resolve.Generics.EnumRep, maybe we could take advantage of the metadata of Rep?

[nalchevanidze]

thank you i will fix it soon. i knew that this part of code was not written properly. i found better way to validate Union types with Generic Rep so i will update Enum decoding.
pull request will be soon.

[nalchevanidze]

old implementation decoded enums could not decode properly enums more then 3 constructors, now it will

[nalchevanidze]

@horus thank you for finding this Bug ;)

[nalchevanidze]

fixed

[horus]

@nalchevanidze
I can confirm this merge solved my problem.
Thank you very much for your help!