Manage .tasty files in Scala 3

main/src/main/scala/sbt/Defaults.scala

@@ -88,6 +88,7 @@ import sbt.util.InterfaceUtil.{ t2, toJavaFunction => f1 }
 import sbt.util._
 import sjsonnew._
 import sjsonnew.support.scalajson.unsafe.Converter
+import xsbti.compile.TastyFiles
 import xsbti.{ FileConverter, Position }
 
 import scala.collection.immutable.ListMap
@@ -681,6 +682,7 @@ object Defaults extends BuildCommon {
   // must be a val: duplication detected by object identity
   private[this] lazy val compileBaseGlobal: Seq[Setting[_]] = globalDefaults(
     Seq(
+      auxiliaryClassFiles := Nil,
       incOptions := IncOptions.of(),
       classpathOptions :== ClasspathOptionsUtil.boot,
       classpathOptions in console :== ClasspathOptionsUtil.repl,
@@ -876,9 +878,14 @@ object Defaults extends BuildCommon {
       compileAnalysisTargetRoot.value / compileAnalysisFilename.value
     },
     externalHooks := IncOptions.defaultExternal,
+    auxiliaryClassFiles ++= {
+      if (ScalaArtifacts.isScala3(scalaVersion.value)) List(TastyFiles.instance)
+      else Nil
+    },
     incOptions := {
       val old = incOptions.value
       old
+        .withAuxiliaryClassFiles(auxiliaryClassFiles.value.toArray)
         .withExternalHooks(externalHooks.value)
         .withClassfileManagerType(
           Option(

main/src/main/scala/sbt/Keys.scala

@@ -248,6 +248,7 @@ object Keys {
   val aggregate = settingKey[Boolean]("Configures task aggregation.").withRank(BMinusSetting)
   val sourcePositionMappers = taskKey[Seq[xsbti.Position => Option[xsbti.Position]]]("Maps positions in generated source files to the original source it was generated from").withRank(DTask)
   private[sbt] val externalHooks = taskKey[ExternalHooks]("The external hooks used by zinc.")
+  val auxiliaryClassFiles = taskKey[Seq[AuxiliaryClassFiles]]("The auxiliary class files that must be managed by Zinc (for instance the TASTy files)")
   val fileConverter = settingKey[FileConverter]("The file converter used to convert between Path and VirtualFile")
   val allowMachinePath = settingKey[Boolean]("Allow machine-specific paths during conversion.")
   val reportAbsolutePath = settingKey[Boolean]("Report absolute paths during compilation.")