ducktape 0.2.x

ducktape 是一个为 Scala 3 提供无样板代码和可配置的 case class 和枚举/密封特质之间转换的库。直接受到 chimney 的启发。

如果这个项目引起了你的兴趣，请给个 🌟 - 虽然这些东西没什么实际价值，但还是能给我带来多巴胺的快感。

安装

libraryDependencies += "io.github.arainko" %% "ducktape" % "0.2.4"

// 或者如果你使用 Scala.js 或 Scala Native
libraryDependencies += "io.github.arainko" %%% "ducktape" % "0.2.4"

注意：版本方案 设置为 early-semver

你现在浏览的是 ducktape 0.2.x 的文档，如果你在找 0.1.x 的文档，请访问这里：https://github.com/arainko/ducktape/tree/series/0.1.x

文档

前往文档站点！

示例说明

ducktape 的目标是无痛地在结构相似的 case class/枚举/密封特质之间进行转换：

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

// 假设这是某种线路模型 - JSON、protobuf、avro 等等...
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( // <-- 字段重新排序 
    lastName: String,
    firstName: String,
    status: Option[domain.Status], // <-- 域模型中的 'status' 是可选的
    paymentMethods: Vector[domain.Payment], // <-- 集合类型从 List 变为 Vector
    updatedAt: Option[Instant],
  )

  enum Status:
    case Registered, PendingRegistration, Removed
    case PendingRemoval // <-- 额外的枚举情况

  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 = 2024-03-10T00:21:33.860394305Z
//     )
//   ),
//   updatedAt = Some(value = 1970-01-01T00:00:00Z)
// )

<details> <summary>点击查看生成的代码</summary>

  (({
    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("未处理的情况。这很可能是ducktape中的一个bug。")
      )
      .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("未处理的情况。这很可能是ducktape中的一个bug。")
    )
    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)

</details>

但是现在想象一下，你的线路模型与你的领域模型略有不同，也许由于某些难以解释的原因，线路模型的PaymentMethod.Card没有name字段...

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) // <-- 噗，'name'不见了
    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))
)

...当你尝试在这两种表示之间进行转换时，编译器现在会对你大喊大叫。

val domainPerson = wirePerson.to[domain.Person]
// 错误：
// MdocApp0.this.wire.PaymentMethod.Card中未找到字段'name' @ Person.paymentMethods.element.at[MdocApp0.this.domain.Payment.Card].name
// given Transformer[Int, String] = int => int.toString
//                                 ^

现在让我们来处理这个问题，首先让我们仔细看看错误消息：

MdocApp0.this.wire.PaymentMethod.Card中未找到字段'name' @ Person.paymentMethods.element.at[MdocApp0.this.domain.Payment.Card].name

特别是@后面的部分：

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

上面的内容基本上是一个指向ducktape无法创建转换的字段/子类型的路径，这些路径可以直接复制粘贴，用于实际修复错误，例如，通过将name字段设置为一个常量值：

val domainPerson = 
  wirePerson
    .into[domain.Person]
    .transform(Field.const(_.paymentMethods.element.at[domain.Payment.Card].name, "常量名称"))
// domainPerson: Person = Person(
//   lastName = "Doe",
//   firstName = "John",
//   status = Some(value = PendingRegistration),
//   paymentMethods = Vector(
//     Cash,
//     PayPal(email = "john@doe.com"),
//     Card(
//       name = "常量名称",
//       digits = 12345L,
//       expires = 2024-03-10T00:21:33.864184449Z
//     )
//   ),
//   updatedAt = Some(value = 1970-01-01T00:00:00Z)
// )

<details> <summary>点击查看生成的代码</summary>

  {
    val AppliedBuilder_this: AppliedBuilder[Person, Person] = into[Person](MdocApp2.this.wirePerson1)[MdocApp2.this.domain.Person]

    {
      val value$proxy3: Person = AppliedBuilder_this.inline$value
{
  val paymentMethods$4: Vector[Payment] = value$proxy3.paymentMethods
    .map[Payment]((src: PaymentMethod) =>
      如果 (src.isInstanceOf[Card])
        new Card(name = "固定名称", digits = src.asInstanceOf[Card].digits, expires = src.asInstanceOf[Card].expires)
      否则如果 (src.isInstanceOf[PayPal]) new PayPal(email = src.asInstanceOf[PayPal].email)
      否则如果 (src.isInstanceOf[Cash.type]) MdocApp2.this.domain.Payment.Cash
      否则 throw new RuntimeException("未处理的情况。这很可能是ducktape中的一个错误。")
    )
    .to[Vector[Payment]](iterableFactory[Payment])
  val status$4: Some[Status] = Some.apply[Status](
    如果 (value$proxy3.status.isInstanceOf[Registered.type]) MdocApp2.this.domain.Status.Registered
    否则如果 (value$proxy3.status.isInstanceOf[PendingRegistration.type]) MdocApp2.this.domain.Status.PendingRegistration
    否则如果 (value$proxy3.status.isInstanceOf[Removed.type]) MdocApp2.this.domain.Status.Removed
    否则 throw new RuntimeException("未处理的情况。这很可能是ducktape中的一个错误。")
  )
  new Person(
    lastName = value$proxy3.lastName,
    firstName = value$proxy3.firstName,
    status = status$4,
    paymentMethods = paymentMethods$4,
    updatedAt = value$proxy3.updatedAt
  )
}: Person
}: Person
}