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scalacase-class

Is actually possible to deprecate Scala case class fields?

Given

case class Fruit(name: String, colour: String)

I'd like to deprecate the case class field colour.

I tried to achieve the former by both employing Scala @deprecated

case class Fruit(name: String, @deprecated("message", "since") colour: String)

and Java @Deprecated annotation

case class Fruit(
  name: String, 
  /* @Deprecated with some message here */
  @(Deprecated @field) 
  colour: String
)

Unfortunately I wasn't able to make colour deprecated in any case and I'm not able to find any resource on that.

Indeed, I can achieve the same task using other approaches, e.g. by relaxing my case class to a normal class and provide a getter for colour and make the latter deprecated, but I would like to know if deprecating case class fields is actually not possible and -- eventually -- the reason why.

Thank you.

UPDATE

As Mike rightly pointed out, colour is a required field for a case class, so the sense of setting this attribute to deprecated is arguable. I'd like to deprecate colour , since I'm now providing colour information from another construct, I want to keep the user knowing that colour is not the right instance by where fetch that information, and I will remove it from Fruit in next releases.

By now, I'd just like warn users to not fetch colour information from the Fruit attribute and, temporarily, I don't really care if they can create instances of fruit with colour information.

UPDATE 2

As Alexey said, I do have the deprecated warning at compile time. But why can't I observe the deprecation in my IDE code as well as I'd deprecating a method, then? I'd expect something like the following

val fruit = Fruit("peer", "green")
val colour = fruit.colour

I'm using IntelliJ.

Solution

  • Your first version seems to work fine: if you paste 

    case class Fruit(name: String, @deprecated("message", "since") colour: String)

println(Fruit("", "").colour)

    at https://scastie.scala-lang.org/, you'll see the deprecation warning. Of course, you need to access the field, whether directly or through an extractor:

    Fruit("", "") match { case Fruit(x, y) => y }

    will also warn.

    That IDEA doesn't show colour as deprecated is I believe just a bug. In general it's quite unreliable in showing errors and warnings in Scala code inline and you should always check by actually building the project.