Weird regression in ZIO Config 4 with the derived config

[alphaho]

I was trying to upgrade ZIO Config from 3.0.6 to 4.0.0-RC16 and found a weird regression that I believe is related to the automatic derivation. Attached is the minimum reproduction of the issue.

With the below snippet, it will fail with the test case 3 and 5, while the rest would succeed.

This issue seems to be related to the names of the ADT. From below snippet, we can find different combinations of them, each with different ordering from the alphabet.

import zio.config.magnolia._
import zio.config.yaml.YamlConfigProvider
import zio.config.{ConfigOps, read}
import zio.test._

object ZioConfigTest extends ZIOSpecDefault {

  object ConfigThatWorks1 {
    sealed trait SubConfig

    object SubConfig {
      @name("empty")
      case object Empty extends SubConfig

      @name("some")
      case class F( // "F" comes after "E" (from "Empty") in the alphabet
        map: Map[String, Int]
      ) extends SubConfig
    }

    case class ParentConfig(conf: SubConfig)

    val parentConfig: Config[ParentConfig] = DeriveConfig.deriveConfig[ParentConfig]
  }

  object ConfigThatDoesNotWork1 {
    sealed trait SubConfig

    object SubConfig {
      @name("empty")
      case object Empty extends SubConfig

      @name("some")
      case class D( // "D" comes before "E" (from "Empty") in the alphabet
        map: Map[String, Int]
      ) extends SubConfig
    }

    case class ParentConfig(conf: SubConfig)

    val parentConfig: Config[ParentConfig] = DeriveConfig.deriveConfig[ParentConfig]
  }

  object ConfigThatDoesNotWork2 {
    sealed trait SubConfig

    object SubConfig {
      @name("empty")
      case object Empty extends SubConfig

      @name("some")
      case class E( // "E" is the same as "E" (from "Empty") in the alphabet
        map: Map[String, Int]
      ) extends SubConfig
    }

    case class ParentConfig(conf: SubConfig)

    val parentConfig: Config[ParentConfig] = DeriveConfig.deriveConfig[ParentConfig]
  }

  override def spec: Spec[TestEnvironment with Scope, Any] = suite("ZioConfigTest")(
    suite("suite 1: config that works - ConfigThatWorks1")(
      test("case 1: should be able to parse as `empty`") {
        val yaml =
          """
            |conf:
            |  empty
            |""".stripMargin

        val expected = ConfigThatWorks1.ParentConfig(
          ConfigThatWorks1.SubConfig.Empty
        )

        assertConfig(ConfigThatWorks1.parentConfig)(yaml, expected)
      },
      test("case 2: should be able to parse as `some`") {
        val yaml =
          """
            |conf:
            |  some:
            |    map:
            |      abc: 123
            |""".stripMargin

        val expected = ConfigThatWorks1.ParentConfig(
          ConfigThatWorks1.SubConfig.F(
            Map("abc" -> 123)
          )
        )

        assertConfig(ConfigThatWorks1.parentConfig)(yaml, expected)
      }
    ),
    suite("suite 2: config that works - ConfigThatDoesNotWork1")(
      test("case 3: should be able to parse as `empty`") {
        val yaml =
          """
            |conf:
            |  empty
            |""".stripMargin

        val expected = ConfigThatDoesNotWork1.ParentConfig(
          ConfigThatDoesNotWork1.SubConfig.Empty
        )

        assertConfig(ConfigThatDoesNotWork1.parentConfig)(yaml, expected)
      },
      test("case 4: should be able to parse as `some`") {
        val yaml =
          """
            |conf:
            |  some:
            |    map:
            |      abc: 123
            |""".stripMargin

        val expected = ConfigThatDoesNotWork1.ParentConfig(
          ConfigThatDoesNotWork1.SubConfig.D(
            Map("abc" -> 123)
          )
        )

        assertConfig(ConfigThatDoesNotWork1.parentConfig)(yaml, expected)
      }
    ),
    suite("suite 3: config that works - ConfigThatDoesNotWork2")(
      test("case 5: should be able to parse as `empty`") {
        val yaml =
          """
            |conf:
            |  empty
            |""".stripMargin

        val expected = ConfigThatDoesNotWork2.ParentConfig(
          ConfigThatDoesNotWork2.SubConfig.Empty
        )

        assertConfig(ConfigThatDoesNotWork2.parentConfig)(yaml, expected)
      },
      test("case 6: should be able to parse as `some`") {
        val yaml =
          """
            |conf:
            |  some:
            |    map:
            |      abc: 123
            |""".stripMargin

        val expected = ConfigThatDoesNotWork2.ParentConfig(
          ConfigThatDoesNotWork2.SubConfig.E(
            Map("abc" -> 123)
          )
        )

        assertConfig(ConfigThatDoesNotWork2.parentConfig)(yaml, expected)
      }
    )
  )

  private def assertConfig[T](config: Config[T])(yaml: String, expected: T): IO[Config.Error, TestResult] = {
    val source = YamlConfigProvider.fromYamlString(yaml)

    for {
      result <- read(config from source)
    } yield assertTrue(result == expected)
  }
}

Environment:

• Scala 2.13.11
• ZIO Config 4.0.0-RC16
• ZIO 2.0.15
• Windows 11