Add CrossVersionExtra.isBinaryCompatible utility

.gitignore

@@ -4,4 +4,9 @@ __pycache__
 
 scripted-test/src/sbt-test/*/*/project/build.properties
 scripted-test/src/sbt-test/*/*/project/plugins.sbt
+
+.idea
+.bloop
+.metals
+.bsp/
 metals.sbt

core/src/main/scala/sbt/internal/librarymanagement/cross/CrossVersionUtil.scala

@@ -84,6 +84,23 @@ object CrossVersionUtil {
     case _ => full
   }
 
+  // Uses the following rules:
+  //
+  //   - Forwards and backwards compatibility is guaranteed for Scala 2.N.x (https://docs.scala-lang.org/overviews/core/binary-compatibility-of-scala-releases.html)
+  //
+  //   - A Scala compiler in version 3.x1.y1 is able to read TASTy files produced by another compiler in version 3.x2.y2 if x1 >= x2 (https://docs.scala-lang.org/scala3/reference/language-versions/binary-compatibility.html)
+  //
+  //   - For non-stable Scala 3 versions, compiler versions can read TASTy in an older stable format but their TASTY versions are not compatible between each other even if the compilers have the same minor version (https://docs.scala-lang.org/scala3/reference/language-versions/binary-compatibility.html)
+  //
+  private[sbt] def isBinaryCompatibleWith(newVersion: String, origVersion: String): Boolean = {
+    (newVersion, origVersion) match {
+      case (NonReleaseV_n("2", nMin, _, _), NonReleaseV_n("2", oMin, _, _)) => nMin == oMin
+      case (ReleaseV("3", nMin, _, _), ReleaseV("3", oMin, _, _))           => nMin.toInt >= oMin.toInt
+      case (NonReleaseV_1("3", nMin, _, _), ReleaseV("3", oMin, _, _))      => nMin.toInt > oMin.toInt
+      case _                                                                => newVersion == origVersion
+    }
+  }
+
   def binaryScalaVersion(full: String): String = {
     if (ScalaArtifacts.isScala3(full)) binaryScala3Version(full)
     else

core/src/main/scala/sbt/librarymanagement/CrossVersionExtra.scala

@@ -9,7 +9,7 @@ private[librarymanagement] abstract class CrossVersionFunctions {
 
   /** Compatibility with 0.13 */
   @deprecated(
-    "use CrossVersion.disabled instead. prior to sbt 1.3.0, Diabled did not work without apply(). sbt/sbt#4977",
+    "use CrossVersion.disabled instead. prior to sbt 1.3.0, Disabled did not work without apply(). sbt/sbt#4977",
     "1.3.0"
   )
   final val Disabled = sbt.librarymanagement.Disabled
@@ -235,4 +235,10 @@ private[librarymanagement] abstract class CrossVersionFunctions {
    * Full sbt versions earlier than [[sbt.librarymanagement.CrossVersion.TransitionSbtVersion]] are returned as is.
    */
   def binarySbtVersion(full: String): String = CrossVersionUtil.binarySbtVersion(full)
+
+  /**
+   * Returns `true` if a project targeting version `origVersion` can run with version `newVersion`.
+   */
+  def isBinaryCompatibleWith(newVersion: String, origVersion: String): Boolean =
+    CrossVersionUtil.isBinaryCompatibleWith(newVersion, origVersion)
 }

core/src/test/scala/sbt/librarymanagement/CrossVersionTest.scala

@@ -284,6 +284,55 @@ class CrossVersionTest extends UnitSpec {
     patchVersion("2.11.8-X1.5-bin-extra") shouldBe Some("artefact_2.11.8-X1.5")
   }
 
+  "isBinaryCompatibleWith" should "for (2.10.4, 2.10.5) return true" in {
+    isBinaryCompatibleWith("2.10.4", "2.10.5") shouldBe true
+  }
+  it should "for (2.10.6, 2.10.5) return true" in {
+    isBinaryCompatibleWith("2.10.6", "2.10.5") shouldBe true
+  }
+  it should "for (2.11.0, 2.10.5) return false" in {
+    isBinaryCompatibleWith("2.11.0", "2.10.5") shouldBe false
+  }
+  it should "for (3.0.0, 2.10.5) return false" in {
+    isBinaryCompatibleWith("3.0.0", "2.10.5") shouldBe false
+  }
+  it should "for (3.0.0, 3.1.0) return false" in {
+    isBinaryCompatibleWith("3.0.0", "3.1.0") shouldBe false
+  }
+  it should "for (3.1.0, 3.0.0) return true" in {
+    isBinaryCompatibleWith("3.1.0", "3.0.0") shouldBe true
+  }
+  it should "for (3.1.0, 3.1.1) return true" in {
+    isBinaryCompatibleWith("3.1.0", "3.1.1") shouldBe true
+  }
+  it should "for (3.1.1, 3.1.0) return true" in {
+    isBinaryCompatibleWith("3.1.1", "3.1.0") shouldBe true
+  }
+  it should "for (2.10.0-M1, 2.10.5) return true" in {
+    isBinaryCompatibleWith("2.10.0-M1", "2.10.5") shouldBe true
+  }
+  it should "for (2.10.5, 2.10.0-M1) return true" in {
+    isBinaryCompatibleWith("2.10.5", "2.10.0-M1") shouldBe true
+  }
+  it should "for (2.10.0-M1, 2.10.0-M2) return true" in {
+    isBinaryCompatibleWith("2.10.0-M1", "2.10.0-M2") shouldBe true
+  }
+  it should "for (2.10.0-M1, 2.11.0-M1) return false" in {
+    isBinaryCompatibleWith("2.10.0-M1", "2.11.0-M1") shouldBe false
+  }
+  it should "for (3.1.0-M1, 3.0.0) return true" in {
+    isBinaryCompatibleWith("3.1.0-M1", "3.0.0") shouldBe true
+  }
+  it should "for (3.1.0-M1, 3.1.0) return false" in {
+    isBinaryCompatibleWith("3.1.0-M1", "3.1.0") shouldBe false
+  }
+  it should "for (3.1.0-M1, 3.1.0-M2) return false" in {
+    isBinaryCompatibleWith("3.1.0-M1", "3.1.0-M2") shouldBe false
+  }
+  it should "for (3.1.0-M2, 3.1.0-M1) return false" in {
+    isBinaryCompatibleWith("3.1.0-M2", "3.1.0-M1") shouldBe false
+  }
+
   private def constantVersion(value: String) =
     CrossVersion(CrossVersion.constant(value), "dummy1", "dummy2") map (fn => fn("artefact"))