Scala Case Class Evolution

EXPERIMENTAL

With Scala developer can't extends case classes.

That's an axiom.

But sometimes, especially if you, like me, work with big data, you really want scala could do that. Otherwise you stuck with doing boilerplate like this.

case class User(
  id: String,
  firstName: String,
  middleName: Option[String],
  lastName: String,
  ... // ton of properties 
)

case class BankUser(
  id: String,
  firstName: String,
  middleName: Option[String],
  lastName: String,
  ... // ton of properties

  bank: String,
  bankAccount: String,
  bankSwift: String,
  bankAccountCreatedAt: LocalDate
)

With the library I wanted to introduce this boilerplate gets reduced.

@evolve(User)
case class BankUser(
  bank: String,
  bankAccount: String,
  bankSwift: String,
  bankAccountCreatedAt: LocalDate)

Sounds good so far?

The resulted class definition will be the same as an example from previous snippet. With even one helper method added withUser, which takes a User and applies it to BankUser.

There also 2 extra features.

• we can reduce case class definition by removing unnecessary fields
• we can rename fields

@evolve(from = User, removed = Set("middleName"), renamed = Map("id" -> "userId"))
case class UserV2()

Even though it may look cool, there is a huge obstacle. IDE support is absent. Code in IDE will be all highlighted and look ugly.

Apache Spark

It can be used with Apache Spark to define schemas. Dataset API.

Also with a little trick it might be used with Frameless. In order to use it with Frameless one need to build model separately from code using it. Consider separate module or separate library.

TODO

• same name, but type changed scenario