Handle Scala LTS and Next version update

Scala Steward now distinguishes between Scala Next and Scala LTS.

When the current Scala 3 versions is below 3.4.0 no updates to a newer Scala Next version will be created. But updates to newer Scala 3.3.x version will be created.

If the current version is already a Scala Next version (3.4.x), updates to newer Scala Next versions will be created.

In the future the `versionLine` property can be used to identify LTS and Next version. (scala/scala3#19986)

modules/core/src/main/resources/default.scala-steward.conf

@@ -30,10 +30,10 @@ postUpdateHooks = [
 updates.ignore = [
   // Artifacts below are ignored because they are not yet announced.
 
-  // No upgrades to non LTS versions
-  { groupId = "org.scala-lang", artifactId = "scala3-compiler",     version = { prefix = "3.4." } },
-  { groupId = "org.scala-lang", artifactId = "scala3-library",      version = { prefix = "3.4." } },
-  { groupId = "org.scala-lang", artifactId = "scala3-library_sjs1", version = { prefix = "3.4." } },
+  // Ignore the next Scala 3 Next version until it is announced.
+  { groupId = "org.scala-lang", artifactId = "scala3-compiler",     version = { exact = "3.4.2" } },
+  { groupId = "org.scala-lang", artifactId = "scala3-library",      version = { exact = "3.4.2" } },
+  { groupId = "org.scala-lang", artifactId = "scala3-library_sjs1", version = { exact = "3.4.2" } },
 
   // Ignore the next Scala 3 LTS version until it is announced.
   { groupId = "org.scala-lang", artifactId = "scala3-compiler",     version = { exact = "3.3.4" } },

modules/core/src/main/scala/org/scalasteward/core/data/package.scala

@@ -19,14 +19,23 @@ package org.scalasteward.core
 package object data {
   val scalaLangGroupId: GroupId = GroupId("org.scala-lang")
 
-  val scalaLangModules: List[(GroupId, ArtifactId)] =
+  val scala2LangModules: List[(GroupId, ArtifactId)] =
     List(
       (scalaLangGroupId, ArtifactId("scala-compiler")),
       (scalaLangGroupId, ArtifactId("scala-library")),
       (scalaLangGroupId, ArtifactId("scala-reflect")),
-      (scalaLangGroupId, ArtifactId("scalap")),
+      (scalaLangGroupId, ArtifactId("scalap"))
+    )
+
+  val scala3LangModules: List[(GroupId, ArtifactId)] =
+    List(
       (scalaLangGroupId, ArtifactId("scala3-compiler")),
       (scalaLangGroupId, ArtifactId("scala3-library")),
       (scalaLangGroupId, ArtifactId("scala3-library_sjs1"))
     )
+
+  val scalaLangModules: List[(GroupId, ArtifactId)] =
+    scala2LangModules ++ scala3LangModules
+
+  val scalaNextMinVersion: Version = Version("3.4.0")
 }

modules/core/src/main/scala/org/scalasteward/core/update/FilterAlg.scala

@@ -54,6 +54,7 @@ object FilterAlg {
         case NotAllowedByConfig(_)      => "not allowed by config"
         case NoSuitableNextVersion(_)   => "no suitable next version"
         case VersionOrderingConflict(_) => "version ordering conflict"
+        case IgnoreScalaNext(_)         => "not upgrading from Scala LTS to Next version"
       }
   }
 
@@ -62,9 +63,30 @@ object FilterAlg {
   final case class NotAllowedByConfig(update: Update.ForArtifactId) extends RejectionReason
   final case class NoSuitableNextVersion(update: Update.ForArtifactId) extends RejectionReason
   final case class VersionOrderingConflict(update: Update.ForArtifactId) extends RejectionReason
+  final case class IgnoreScalaNext(update: Update.ForArtifactId) extends RejectionReason
 
   def localFilter(update: Update.ForArtifactId, repoConfig: RepoConfig): FilterResult =
-    repoConfig.updates.keep(update).flatMap(globalFilter(_, repoConfig))
+    repoConfig.updates.keep(update).flatMap(scalaLTSFilter).flatMap(globalFilter(_, repoConfig))
+
+  def scalaLTSFilter(update: Update.ForArtifactId): FilterResult =
+    if (!isScala3Lang(update))
+      Right(update)
+    else {
+      if (update.currentVersion >= scalaNextMinVersion) {
+        // already on Scala Next
+        Right(update)
+      } else {
+        val filteredVersions = update.newerVersions.filterNot(_ >= scalaNextMinVersion)
+        if (filteredVersions.nonEmpty)
+          Right(update.copy(newerVersions = Nel.fromListUnsafe(filteredVersions)))
+        else Left(IgnoreScalaNext(update))
+      }
+    }
+
+  def isScala3Lang(update: Update.ForArtifactId): Boolean =
+    scala3LangModules.exists { case (g, a) =>
+      update.groupId == g && update.artifactIds.exists(_ == a)
+    }
 
   private def globalFilter(update: Update.ForArtifactId, repoConfig: RepoConfig): FilterResult =
     selectSuitableNextVersion(update, repoConfig).flatMap(checkVersionOrdering)

modules/core/src/test/scala/org/scalasteward/core/update/FilterAlgTest.scala

@@ -246,4 +246,24 @@ class FilterAlgTest extends FunSuite {
     val dependency = "org.typelevel".g % ("cats-effect", "cats-effect_2.12").a % "1.0.0"
     assert(isDependencyConfigurationIgnored(dependency.copy(configurations = Some("scalafmt"))))
   }
+
+  test("scalaLTSFilter: LTS") {
+    val update = ("org.scala-lang".g % "scala3-compiler".a % "3.3.3" %> Nel.of("3.4.0")).single
+    assertEquals(scalaLTSFilter(update), Left(IgnoreScalaNext(update)))
+  }
+
+  test("scalaLTSFilter: Next") {
+    val update = ("org.scala-lang".g % "scala3-compiler".a % "3.4.0" %> Nel.of("3.4.1")).single
+    assertEquals(scalaLTSFilter(update), Right(update))
+  }
+
+  test("isScala3Lang: true") {
+    val update = ("org.scala-lang".g % "scala3-compiler".a % "3.3.3" %> Nel.of("3.4.0")).single
+    assert(isScala3Lang(update))
+  }
+
+  test("isScala3Lang: false") {
+    val update = ("org.scala-lang".g % "scala-compiler".a % "2.13.11" %> Nel.of("2.13.12")).single
+    assert(!isScala3Lang(update))
+  }
 }