add "import scala.jdk.CollectionConverters" option in scalapb compiler-plugin?

[xuwei-k]

scala.collection.JavaConverters deprecated since Scala 2.13.

I think we should add new option for which class to use scala.jdk.CollectionConverters or scala.collection.JavaConverters for avoid deprecation warnings.

something like

  if (useJdkCollectionConverter) {
    printer.add("import scala.jdk.CollectionConverters._")
  } else {
    printer.add("import scala.collection.JavaConverters._")
  }

ScalaPB/compiler-plugin/src/main/scala/scalapb/compiler/ProtobufGenerator.scala

Lines 1651 to 1652 in 34993f9

	.when(javaConverterImport)(
	_.add("import scala.collection.JavaConverters._").add()

[giiita]

As a similar problem, default Seq has been changed from scala.collection.Seq to scala.collection.immutable.Seq from scala2.13'.
This will require a toSeq call during model conversion.

[xuwei-k]

we should add new option

Alternatively, create custom compat converter object in scalapb-runtime 🤔

scala/scala-collection-compat#208

[thesamet]

@xuwei-k yes! that would be my preference, so the same source compiles for all versions of Scala.

@giiita Can you clarify what problem you are referring to? Is there a warning you are seeing?

[giiita]

@thesamet
No, there is no warning.

There is such an interface.

message AnyList {
    repeated string values = 1;
}

final case class AnyList(values: _root_.scala.collection.Seq[String])

In 2.12, the default Seq is scala.collection.Seq.

type Seq[+A] = scala.collection.Seq[A]
val Seq = scala.collection.Seq

So this worked.

case class MyList(values: Seq[String])

MyList(AnyList().values)

In contrast, in 2.13 it has been changed to scala.collection.immutable.Seq.

@migration("scala.Seq is now scala.collection.immutable.Seq instead of scala.collection.Seq", "2.13.0")
type Seq[+A] = scala.collection.immutable.Seq[A]
val Seq = scala.collection.immutable.Seq

so conversion by toSeq is necessary.

case class MyList(values: Seq[String])

MyList(AnyList().values.toSeq)

Since this breaks compatibility with 2.12, I think it is preferable to change the automatically generated code to immutable.Seq.

[thesamet]

@giiita Both MyList.values and AnyList.values are scala.colleciton.Seq in both Scala 2.12 and Scala 2.13. Therefore, .toSeq is not necessary for either version of Scala. I might be missing something - if so, can you please start a separate issue so the discussion stays focused here stays focused on the JavaConverters warning?