Pureconfig Typesafe Config with sealed abstract case class

Question

I am trying to incorporate Pureconfig in my use case for typesafe configurations. Been successful in mapping HOCON .conf to case class types. However, if I have to constrain my types with no side-effects on the object definition side (i.e., supress default apply() and copy()), I am using following definition approach for case class:

sealed abstract case class someConfig(name:String)

object someConfig{
    def apply(name:String):Option[someConfig]={
        if(Option(name).isDefined && name.nonEmpty){
            Some(new someConfig(name){})
        } else {
            None
        }
    }
}

To support Option[_] types, I am considering having an implicit ConfigReader. This approach seems to work, with a bit more for me to address config-keys to object mapping and instantiation.

Examples that I have searched upon so far doesn't seem to resonate this need. However, do see use of Option[_] on the object members. Tried to walk through the code samples in Pureconfig git repo.

Could someone suggest an approach where Option[T] could be supported, where T is a composite custom type? And I don't have to deal with member variable name to config key mapping, etc. i.e., avoid necessary boilerplate!

Leif Wickland · Accepted Answer · 2018-01-11T00:57:14.330

0

Because you've hidden the constructor for your class in order to channel validation through the apply, you'll have to manually construct a ConfigReader. I believe that's about as simple as putting this in your companion object:

implicit val configReader = 
  pureconfig.ConfigReader.fromNonEmptyStringOpt[someConfig](apply)

Alternatively, you could name the class implementing your abstract type in which case PureConfig's automatic derivation for sealed families would magically create the ConfigReader for you.

edited Jan 11 '18 at 00:57

answered Jan 11 '18 at 00:51

Leif Wickland

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marking this as closed. Alternate approach (in-line to the above link on automatic derivation...) did work. That meets my need to suppress default apply() and copy(), besides being able to auto-magically map between config to desired ADT. For extensibility could also have a abstract class extend the trait, to be able to generalize the serialization requirement (override def toString()). – ganaakruti Jan 11 '18 at 21:04
Further, settled with approach of having a `case class` with a copy(...) method that matches the only constructor that I needed to allow. This solved the issue of suppressing default apply() and copy() methods. As a refinement, I could define a macro that can be applied to ADT's to include a matching copy(...) method. Scala version that I tried - 2.12.3 – ganaakruti Jan 12 '18 at 03:23

Pureconfig Typesafe Config with sealed abstract case class

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