Custom error message for Assertion

[SvenW]

When adding a new type e.g:

  object Name extends Subtype[String] {
    override def assertion          = assert {
      hasLength(greaterThanOrEqualTo(1))
    }

It would be nice to be able to set a custom error message that's a bit more user friendly if the assertion fails. Right now this assertion would give us did not satisfy hasLength(greaterThanOrEqualTo(1)), which isn't that user friendly if returned to an actual user. It's possible to remap the error if we use make, e.g Name.make("my name") but that's a bit to easy to forget. Would it make sense to be able to set a custom error message on an Assertion?

[guizmaii]

Alternatively, you can use assertCustom

  object Name extends Subtype[String] {
    override def assertion = assertCustom { str =>
      if (str.trim.size >= 1) Right(()) else Left(AssertionError.Failure("This is an error"))
    }
  }

See https://github.com/zio/zio-prelude/blob/series/2.x/core-tests/shared/src/test/scala-2.12-2.13/zio/prelude/NewtypeSpecTypes212.scala#L7-L9

Note that this is in Scala2. In Scala3, the syntax is a bit different: https://github.com/zio/zio-prelude/blob/series/2.x/core-tests/shared/src/test/scala-3/zio/prelude/NewtypeSpecTypes.scala#L90-L96

[SvenW]

Alternatively, you can use assertCustom

  object Name extends Subtype[String] {
    override def assertion = assertCustom { str =>
      if (str.trim.size >= 1) Right(()) else Left(AssertionError.Failure("This is an error"))
    }
  }

See https://github.com/zio/zio-prelude/blob/series/2.x/core-tests/shared/src/test/scala-2.12-2.13/zio/prelude/NewtypeSpecTypes212.scala#L7-L9

Note that this is in Scala2. In Scala3, the syntax is a bit different: https://github.com/zio/zio-prelude/blob/series/2.x/core-tests/shared/src/test/scala-3/zio/prelude/NewtypeSpecTypes.scala#L90-L96

Thanks. I settled on this for now

  object Name extends Subtype[String] {
    override def assertion          = assertCustom { str =>
      hasLength(greaterThanOrEqualTo(1))(str).fold(_ => Left(AssertionError.Failure("can't be empty")), _ => Right(()))
    }
```. Would however still be nice to be able to just define an error message