使用 circe 和 Http4s 时精炼类型的解码器

Question

I am trying to use refined types for a case class but couldn't figure out how the encoder will actually work. For json parsing circe is used with https4s library.

  type AgeT = Int Refined Interval.ClosedOpen[0,100]
  type NameT = String Refined NonEmptyString
  case class Person(name: NameT,age: AgeT)
  object Person  {
    implicit val encoder: Encoder[Person] =  deriveEncoder[Person]
    implicit val decoder: Decoder[Person] =  deriveDecoder[Person]
  }

  implicit val decoder = jsonOf[IO,Person]
  val jsonWithValidationService = HttpRoutes.of[IO] {
    case req @ POST -> Root / "jsonBody" =>
        for {
          c <- req.as[Person]
          res <-Ok(c.asJson)
        } yield res
  }.orNotFound

Error

Error:(61, 59) could not find Lazy implicit value of type io.circe.generic.decoding.DerivedDecoder[server.Routes.Person]
    implicit val decoder: Decoder[Person] =  deriveDecoder[Person]

Worst case I need to define my own decoder and parse it. But if there's any other way that can simplify further would be nice.

Answer 1

type NameT = String Refined NonEmptyString

is wrong. Replace it with

type NameT = String Refined NonEmpty

Otherwise NonEmptyString is already String Refined NonEmpty and in NameT you do Refined twice, which is wrong.

Or you can define just

type NameT = NonEmptyString

Don't forget imports

import cats.effect.IO
import eu.timepit.refined.api.Refined
import eu.timepit.refined.numeric.Interval
import eu.timepit.refined.collection.NonEmpty
import eu.timepit.refined.types.string.NonEmptyString
import io.circe.{Decoder, Encoder}
import io.circe.generic.semiauto._
import io.circe.syntax._
import io.circe.refined._
import org.http4s.circe._
import org.http4s.dsl.io._
import org.http4s.implicits._
import org.http4s.HttpRoutes