multipartBody inferring Product as type in wart remover

tapir
1

While working on upgrading our Tapir version I have run into an issue where Wartremover infers a Product type on our multipartbody. I have some example code with the issue:

//> using scala 2.13
//> using lib com.softwaremill.sttp.tapir::tapir-core:1.8.4
//> using lib org.scala-lang.modules::scala-xml:1.3.0
//> using lib io.circe::circe-generic:0.14.6
//> using plugin org.wartremover:::wartremover:3.1.5
//> using option "-P:wartremover:traverser:org.wartremover.warts.Product"

import io.circe.Codec
import io.circe.generic.semiauto.deriveCodec
import sttp.tapir._
import sttp.model.Part
import sttp.tapir.Schema

import java.io.File

object Example {

  final case class Model(int: Int)
  final case class multiExample(model: Model, part: Part[File])

  object Model {
    implicit val modelCodec: Codec[Model] = deriveCodec
    implicit lazy val modelSchema: Schema[Model] = Schema.derived[Model]
  }
  object multiExample {
    implicit lazy val multiExampleSchema: Schema[multiExample] = Schema.derived[multiExample]
  }

  val example =
    endpoint
      .tag("example")
      .post
      .in(multipartBody[multiExample])
}

The above works fine until for any version lower then 0.20.0, but breaks afterwards. Thinking it might just be wartremover, I have tried suppressing the warning, however that resulted in the endpoint not being accessible at all.
In my testing I have also noticed that this only happens if you have a custom class within the class in the multipartBody, e.g. if in the above you change the model: Model to model: String, this will compile without any errors.

Does anyone have any clue as to why this might be, and possibly some kind of answer on how to solve the problem?

2

Sorry for the (very late) reply :slight_smile:

If you still have problems with this … am I guessing right that the model field should be deserialized from JSON?

If so, you’re missing importing the tapir ↔ circe integration, which brings into scope tapir’s codecs (as in sttp.tapir.Codec). Right now, the invocation multipartBody[multiExample] looks for any codec for each field. In case of the model field, no codecs are explicitly imported, so it looks in the defaults - and finds a form-field codec. So this code kind of expects nested forms. By adding import sttp.tapir.json.circe._ I get the correct behavior.

(btw. - everything compiles fine)