Delete checkPluginCross task. Add sourceGenerators for PluginCross (#8897)

build.sbt

@@ -53,7 +53,6 @@ val excludeLint = SettingKey[Set[Def.KeyedInitialize[?]]]("excludeLintKeys")
 Global / excludeLint := (Global / excludeLint).?.value.getOrElse(Set.empty)
 Global / excludeLint += Utils.componentID
 Global / excludeLint += scriptedBufferLog
-Global / excludeLint += checkPluginCross
 Global / excludeLint += nativeImageJvm
 Global / excludeLint += nativeImageVersion
 
@@ -709,12 +708,18 @@ lazy val mainProj = (project in file("main"))
   .settings(
     testedBaseSettings,
     name := "Main",
-    checkPluginCross := {
-      val sv = scalaVersion.value
-      val f = baseDirectory.value / "src" / "main" / "scala" / "sbt" / "PluginCross.scala"
-      if (sv.startsWith("2.12") && !IO.readLines(f).exists(_.contains(s""""$sv""""))) {
-        sys.error(s"PluginCross.scala does not match up with the scalaVersion $sv")
-      }
+    Compile / sourceGenerators += task {
+      val f = (Compile / sourceManaged).value / "sbt" / "PluginCrossExtra.scala"
+      IO.write(
+        f,
+        s"""|package sbt
+            |
+            |private[sbt] trait PluginCrossExtra { self: PluginCross.type =>
+            |  def scala3: String = "${Dependencies.scala3}"
+            |}
+            |""".stripMargin
+      )
+      Seq(f)
     },
     libraryDependencies ++=
       Seq(

main/src/main/scala/sbt/PluginCross.scala

@@ -24,7 +24,7 @@ import ProjectExtra.{ extract, setProject }
 /**
  * Module responsible for plugin cross building.
  */
-private[sbt] object PluginCross {
+private[sbt] object PluginCross extends PluginCrossExtra {
   lazy val pluginSwitch: Command = {
     def switchParser(state: State): Parser[(String, String)] = {
       lazy val switchArgs = token(NotSpace.examples()) ~ (token(
@@ -102,7 +102,7 @@ private[sbt] object PluginCross {
       case VersionNumber(Seq(0, 12, _*), _, _) => "2.9.2"
       case VersionNumber(Seq(0, 13, _*), _, _) => "2.10.7"
       case VersionNumber(Seq(1, 0, _*), _, _)  => "2.12.21"
-      case VersionNumber(Seq(2, _*), _, _)     => "3.8.2"
+      case VersionNumber(Seq(2, _*), _, _)     => scala3
       case _                                   => sys.error(s"Unsupported sbt binary version: $sv")
     }
 }

project/Dependencies.scala

@@ -6,7 +6,6 @@ object Dependencies {
   val scala213 = "2.13.16"
   val scala3 = "3.8.2"
   val scala212 = "2.12.21"
-  val checkPluginCross = settingKey[Unit]("Make sure scalaVersion match up")
   val baseScalaVersion = scala3
   def nightlyVersion: Option[String] =
     sys.env.get("BUILD_VERSION") orElse sys.props.get("sbt.build.version")