Following example doesn't work

[mikkelspring]

Hello, I'm fairly sure I'm using this library correctly, but for some reason the macro is outputting an empty read and write. I first noticed this on my own use case, but it is also replicating with the basic example from the readme.

sealed trait Foo
case class Bar(x: Int) extends Foo
case class Baz(s: String) extends Foo
case class Bah(s: String) extends Foo
implicit val format = Variants.format[Foo]

Leads to

play.api.libs.json.Format[Foo](play.api.libs.json.Reads[Foo](((json) => Impl.this.defaultDiscriminator.reads(json).flatMap( match {

}))), play.api.libs.json.Writes[Foo]( match {

}))
Apply(TypeApply(Select(Select(Select(Select(Ident(TermName("play")), TermName("api")), TermName("libs")), TermName("json")), TermName("Format")), List(Ident(models.Propagate.Foo))), List(Apply(TypeApply(Select(Select(Select(Select(Ident(TermName("play")), TermName("api")), TermName("libs")), TermName("json")), TermName("Reads")), List(Ident(models.Propagate.Foo))), List(Function(List(ValDef(Modifiers(PARAM), TermName("json"), TypeTree(), EmptyTree)), Apply(Select(Apply(Select(Select(This(TypeName("Impl")), TermName("defaultDiscriminator")), TermName("reads")), List(Ident(TermName("json")))), TermName("flatMap")), List(Match(EmptyTree, List())))))), Apply(TypeApply(Select(Select(Select(Select(Ident(TermName("play")), TermName("api")), TermName("libs")), TermName("json")), TermName("Writes")), List(Ident(models.Propagate.Foo))), List(Match(EmptyTree, List())))))

Do you have any ideas about what could be causing this? Thanks!

[mikkelspring]

Sorry, I didn't notice this was from the 2.0 branch.

Now that I've updated to 3.0 I have

sealed trait Foo
case class Bar(s: String, i: Int) extends Foo
case object Baz extends Foo

object Foo {
  implicit val format = oformat[Foo]
}

Error:(35, 32) could not find implicit value for parameter derivedReads: shapeless.Lazy[julienrf.json.derived.DerivedReads[models.Foo]]
implicit val format = oformat[Foo]
^
Error:(35, 32) not enough arguments for method oformat: (implicit derivedReads: shapeless.Lazy[julienrf.json.derived.DerivedReads[models.Foo]], implicit derivedOWrites: shapeless.Lazy[julienrf.json.derived.DerivedOWrites[models.Foo]])play.api.libs.json.OFormat[models.Foo].
Unspecified value parameters derivedReads, derivedOWrites.
implicit val format = oformat[Foo]

                           ^

[mikkelspring]

OK I copied and pasted directly from the test and it worked. For some reason I don't understand, it is required to explicitly specific the OFormat type like so

implicit val format: OFormat[Foo] = oformat[Foo]

Could be added to the docs? Thanks for your work.

[janakagamini]

I have the same exact error (could not find implicit value for parameter... and not enough arguments...), and I cant get rid of it

Here's what my code looks like:

object Foo {
  implicit val format: OFormat[Foo] = derived.oformat[Foo]
}

sealed trait Foo

//object Bar {
//  implicit val format: OFormat[Bar] = derived.oformat[Bar]
//}

case class Bar(s: String) extends Foo

//object Zoo {
//  implicit val format: OFormat[Zoo] = derived.oformat[Zoo]
//}

case class Zoo(i: Int) extends Foo

I get the same result if I un-comment the commented parts as well.

What am I missing?

[julienrf]

It will work if you move the Foo object definition after the case classes.

I’m sorry about that but it seems to be one of the issues of knownDirectSubclasses: https://groups.google.com/d/topic/scala-internals/LRfKffsPxVA/discussion

[janakagamini]

Yes just realized it after I read through the documentation for v2.0.

Now I can compile but I still cant get it to de-serialize a websocket frame (Play 2.5), but that is probably a totally different issue.

Thank you for responding @julienrf