Scala-2-dependsOn-Scala-3 feature with Scala.js

fix 5971

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

@@ -3594,13 +3594,15 @@ object Classpaths {
           depSBV <- (dep.project / scalaBinaryVersion).get(data)
           depCross <- (dep.project / crossVersion).get(data)
         } yield {
-          if (isScala2Scala3Sandwich(sbv, depSBV) && depCross == CrossVersion.binary)
-            depProjId
-              .withCrossVersion(CrossVersion.constant(depSBV))
-              .withConfigurations(dep.configuration)
-              .withExplicitArtifacts(Vector.empty)
-          else
-            depProjId.withConfigurations(dep.configuration).withExplicitArtifacts(Vector.empty)
+          depCross match {
+            case b: CrossVersion.Binary if isScala2Scala3Sandwich(sbv, depSBV) =>
+              depProjId
+                .withCrossVersion(CrossVersion.constant(b.prefix + depSBV))
+                .withConfigurations(dep.configuration)
+                .withExplicitArtifacts(Vector.empty)
+            case _ =>
+              depProjId.withConfigurations(dep.configuration).withExplicitArtifacts(Vector.empty)
+          }
         }
       }
     }

sbt/src/sbt-test/plugins/dotty-sandwich-sjs/app/src/main/scala/app/Main.scala

@@ -0,0 +1,9 @@
+package app
+
+import mylib._
+
+object Main {
+  def main(args: Array[String]): Unit = {
+    println(MyLib.square(5))
+  }
+}

sbt/src/sbt-test/plugins/dotty-sandwich-sjs/build.sbt

@@ -0,0 +1,17 @@
+// TODO use 2.13.4 when it's out
+ThisBuild / scalaVersion := "2.13.4-bin-d526da6"
+
+Global / resolvers += "scala-integration".at("https://scala-ci.typesafe.com/artifactory/scala-integration/")
+
+lazy val scala3code = project
+  .enablePlugins(ScalaJSPlugin)
+  .settings(scalaVersion := "0.27.0-RC1")
+
+lazy val app = project
+  .enablePlugins(ScalaJSPlugin)
+  .dependsOn(scala3code)
+  .settings(
+    libraryDependencies ~= (_.filterNot(_.name.contains("scalajs-compiler"))),
+    addCompilerPlugin("org.scala-js" % "scalajs-compiler_2.13.3" % scalaJSVersion),
+    scalaJSUseMainModuleInitializer := true,
+  )

sbt/src/sbt-test/plugins/dotty-sandwich-sjs/project/plugins.sbt

@@ -0,0 +1,2 @@
+addSbtPlugin("ch.epfl.lamp" % "sbt-dotty" % "0.4.3")
+addSbtPlugin("org.scala-js" % "sbt-scalajs" % "1.3.0")

sbt/src/sbt-test/plugins/dotty-sandwich-sjs/scala3code/src/main/scala/mylib/MyLib.scala

@@ -0,0 +1,5 @@
+package mylib
+
+object MyLib {
+  def square(x: Int): Int = x * x
+}

sbt/src/sbt-test/plugins/dotty-sandwich-sjs/test

@@ -0,0 +1 @@
+> app/run