Infinite <<loop>> when using named fields

[paulyoung]

This data type:

data Foo
  = Bar Foo
  | Baz Foo
  deriving (Generic, ToJSON, ToSchema)

Produces this JSON:

{
  "swagger": "2.0",
  "info": {
    "version": "",
    "title": ""
  },
  "definitions": {
    "Foo": {
      "minProperties": 1,
      "maxProperties": 1,
      "type": "object",
      "properties": {
        "Baz": {
          "$ref": "#/definitions/Foo"
        },
        "Bar": {
          "$ref": "#/definitions/Foo"
        }
      }
    }
  },
  "paths": {}
}

However, if I attempt to name the field like this:

data Foo
  = Bar { _1 :: Foo }
  | Baz { _2 :: Foo }
  deriving (Generic, ToJSON, ToSchema)

I get:

<<loop>>

[paulyoung]

My motivation for using named fields is in an attempt to have the required field populated and managed for me.

I’m hoping that I can later use that to know which type arguments were a Maybe

[fisx]

looks like a legitimate bug to me. do you have time to work on fixing this?

[paulyoung]

@Gabriel439 suggested that this could potentially be fixed using the same approach as in dhall-lang/dhall-haskell#1660

[paulyoung]

I linked to the issue but the PR that fixes it is dhall-lang/dhall-haskell#1825

[paulyoung]

It looks like those changes allow erroring out and breaking the loop but don't actually allow generic deriving of recursive data types.