ducktape 0.2.0-M2

ducktape 0.2.0-M2

The 0.2.x series comes with a lot of improvements, some of them being:

• support for configurations for nested transformations (previously these would need to be their own Transformer instance, no matter how basic the config was),
• the library now reports all of the transformation errors all at once (with copy-pastable hints on how to fix a given error, eg.

No field 'name' found in MdocApp0.this.wire.PaymentMethod.Card @ Person.paymentMethods.element.at[MdocApp0.this.domain.Payment.Card].name

...and many others.

The 0.2.x series also retains source compatibility with the 0.1.x series to the fullest extent possible (there are SOME changes which will be documented in detail some time in the future) - but generally your code should compile and work as is.

This milestone release only contains support for total transformations, fallible transformations are coming soon.

Read on over to see what is actually possible now or read the docs and try it for yourself:

import java.time.Instant
import io.github.arainko.ducktape.*

// imagine this is a wire model of some kind - JSON, protobuf, avro, what have you...
object wire {
  final case class Person(
    firstName: String,
    lastName: String,
    paymentMethods: List[wire.PaymentMethod],
    status: wire.Status,
    updatedAt: Option[Instant],
  )

  enum Status:
    case Registered, PendingRegistration, Removed

  enum PaymentMethod:
    case Card(name: String, digits: Long, expires: Instant)
    case PayPal(email: String)
    case Cash
}

object domain {
  final case class Person( // <-- fields reshuffled 
    lastName: String,
    firstName: String,
    status: Option[domain.Status], // <-- 'status' in the domain model is optional
    paymentMethods: Vector[domain.Payment], // <-- collection type changed from a List to a Vector
    updatedAt: Option[Instant],
  )

  enum Status:
    case Registered, PendingRegistration, Removed
    case PendingRemoval // <-- additional enum case

  enum Payment:
    case Card(name: String, digits: Long, expires: Instant)
    case PayPal(email: String)
    case Cash
}

val wirePerson: wire.Person = wire.Person(
  "John",
  "Doe",
  List(
    wire.PaymentMethod.Cash,
    wire.PaymentMethod.PayPal("john@doe.com"),
    wire.PaymentMethod.Card("J. Doe", 12345, Instant.now)
  ),
  wire.Status.PendingRegistration,
  Some(Instant.ofEpochSecond(0))
)

val domainPerson = wirePerson.to[domain.Person]
// domainPerson: Person = Person(
//   lastName = "Doe",
//   firstName = "John",
//   status = Some(value = PendingRegistration),
//   paymentMethods = Vector(
//     Cash,
//     PayPal(email = "john@doe.com"),
//     Card(
//       name = "J. Doe",
//       digits = 12345L,
//       expires = 2023-12-17T14:54:13.882678035Z
//     )
//   ),
//   updatedAt = Some(value = 1970-01-01T00:00:00Z)
// )

Click to see the generated code

  (({
    val paymentMethods$2: Vector[Payment] = MdocApp.this.wirePerson.paymentMethods
      .map[Payment]((src: PaymentMethod) =>
        if (src.isInstanceOf[Card])
          new Card(
            name = src.asInstanceOf[Card].name,
            digits = src.asInstanceOf[Card].digits,
            expires = src.asInstanceOf[Card].expires
          )
        else if (src.isInstanceOf[PayPal]) new PayPal(email = src.asInstanceOf[PayPal].email)
        else if (src.isInstanceOf[Cash.type]) MdocApp.this.domain.Payment.Cash
        else throw new RuntimeException("Unhandled condition encountered during Coproduct Transformer derivation")
      )
      .to[Vector[Payment]](iterableFactory[Payment])
    val status$2: Some[Status] = Some.apply[Status](
      if (MdocApp.this.wirePerson.status.isInstanceOf[Registered.type]) MdocApp.this.domain.Status.Registered
      else if (MdocApp.this.wirePerson.status.isInstanceOf[PendingRegistration.type])
        MdocApp.this.domain.Status.PendingRegistration
      else if (MdocApp.this.wirePerson.status.isInstanceOf[Removed.type]) MdocApp.this.domain.Status.Removed
      else throw new RuntimeException("Unhandled condition encountered during Coproduct Transformer derivation")
    )
    new Person(
      lastName = MdocApp.this.wirePerson.lastName,
      firstName = MdocApp.this.wirePerson.firstName,
      status = status$2,
      paymentMethods = paymentMethods$2,
      updatedAt = MdocApp.this.wirePerson.updatedAt
    )
  }: Person): Person)

But now imagine that your wire model differs ever so slightly from your domain model, maybe the wire model's PaymentMethod.Card doesn't have the name field for some inexplicable reason...

object wire {
  final case class Person(
    firstName: String,
    lastName: String,
    paymentMethods: List[wire.PaymentMethod],
    status: wire.Status,
    updatedAt: Option[Instant],
  )

  enum Status:
    case Registered, PendingRegistration, Removed

  enum PaymentMethod:
    case Card(digits: Long, expires: Instant) // <-- poof, 'name' is gone
    case PayPal(email: String)
    case Cash
}

val wirePerson: wire.Person = wire.Person(
  "John",
  "Doe",
  List(
    wire.PaymentMethod.Cash,
    wire.PaymentMethod.PayPal("john@doe.com"),
    wire.PaymentMethod.Card(12345, Instant.now)
  ),
  wire.Status.PendingRegistration,
  Some(Instant.ofEpochSecond(0))
)

...and when you try to transform between these two representations the compiler now yells at you.

val domainPerson = wirePerson.to[domain.Person]
// error:
// No field 'name' found in MdocApp0.this.wire.PaymentMethod.Card @ Person.paymentMethods.element.at[MdocApp0.this.domain.Payment.Card].name
//   case Cash
//       ^

Now onto dealing with that, let's first examine the error message:

No field 'name' found in MdocApp0.this.wire.PaymentMethod.Card @ Person.paymentMethods.element.at[MdocApp0.this.domain.Payment.Card].name

especially the part after @:

Person.paymentMethods.element.at[MdocApp0.this.domain.Payment.Card].name

the thing above is basically a path to the field/subtype under which ducktape was not able to create a transformation, these are meant to be copy-pastable for when you're actually trying to fix the error, eg. by setting the name field to a constant value:

val domainPerson = 
  wirePerson
    .into[domain.Person]
    .transform(Field.const(_.paymentMethods.element.at[domain.Payment.Card].name, "CONST NAME"))
// domainPerson: Person = Person(
//   lastName = "Doe",
//   firstName = "John",
//   status = Some(value = PendingRegistration),
//   paymentMethods = Vector(
//     Cash,
//     PayPal(email = "john@doe.com"),
//     Card(
//       name = "CONST NAME",
//       digits = 12345L,
//       expires = 2023-12-17T14:54:13.890982787Z
//     )
//   ),
//   updatedAt = Some(value = 1970-01-01T00:00:00Z)
// )

Click to see the generated code

  {
    val AppliedBuilder_this: AppliedBuilder[Person, Person] = into[Person](MdocApp1.this.wirePerson1)[MdocApp1.this.domain.Person]

    {
      val value$proxy3: Person = AppliedBuilder_this.inline$value

      {
        val paymentMethods$4: Vector[Payment] = value$proxy3.paymentMethods
          .map[Payment]((src: PaymentMethod) =>
            if (src.isInstanceOf[Card])
              new Card(name = "CONST NAME", digits = src.asInstanceOf[Card].digits, expires = src.asInstanceOf[Card].expires)
            else if (src.isInstanceOf[PayPal]) new PayPal(email = src.asInstanceOf[PayPal].email)
            else if (src.isInstanceOf[Cash.type]) MdocApp1.this.domain.Payment.Cash
            else throw new RuntimeException("Unhandled condition encountered during Coproduct Transformer derivation")
          )
          .to[Vector[Payment]](iterableFactory[Payment])
        val status$4: Some[Status] = Some.apply[Status](
          if (value$proxy3.status.isInstanceOf[Registered.type]) MdocApp1.this.domain.Status.Registered
          else if (value$proxy3.status.isInstanceOf[PendingRegistration.type]) MdocApp1.this.domain.Status.PendingRegistration
          else if (value$proxy3.status.isInstanceOf[Removed.type]) MdocApp1.this.domain.Status.Removed
          else throw new RuntimeException("Unhandled condition encountered during Coproduct Transformer derivation")
        )
        new Person(
          lastName = value$proxy3.lastName,
          firstName = value$proxy3.firstName,
          status = status$4,
          paymentMethods = paymentMethods$4,
          updatedAt = value$proxy3.updatedAt
        )
      }: Person
    }: Person
  }