Formatter is giving parse error when deriving stock or anyclass

[Mayank Sharma]

I have a file named Types.hs
And the file contains this

module Types where

import GHC.Generics
import Data.Text
import Data.Aeson

data Create = Create {
    amount          :: Double,
    currency        :: Text,
    id              :: Text,
    description     :: Text
}
deriving stock (Generic, Eq, Show)
deriving anyclass (ToJSON, FromJSON)

I use this command haskell-formatter < Types.hs to format the file.

When I run this it gives

haskell-formatter < Types.hs 
<stdin>:16:14: Parse error: stock

But on building(nix-build or ghcide) there is no error or warning.

Can anyone help

[Benjamin Fischer]

Hi @mayank-17

It looks like you're using language extensions that affect what is considered valid code. The formatter only looks at a given source file when parsing, that is, any extensions configured otherwise are not considered. If you configure the extensions in the source file like this, it works:

+{-# LANGUAGE DeriveAnyClass #-}
+{-# LANGUAGE DerivingStrategies #-}
+
 module Types where
 
 import GHC.Generics
@@ -10,5 +13,5 @@ data Create = Create {
     id              :: Text,
     description     :: Text
 }
-deriving stock (Generic, Eq, Show)
-deriving anyclass (ToJSON, FromJSON)
+  deriving stock (Generic, Eq, Show)
+  deriving anyclass (ToJSON, FromJSON)

Please also note that this project is deprecated. See the deprecation notice with migration guide.

I hope that helps anyway.