Backport Scala 2.13-3.x inter project dependency

Ref https://github.com/sbt/sbt/pull/5767

src/main/scala/sbt/internal/ProjectMatrix.scala

@@ -249,7 +249,8 @@ object ProjectMatrix {
             crossTarget := Keys.target.value,
             sourceDirectory := base.getAbsoluteFile / "src",
             inConfig(Compile)(makeSources(nonScalaDirSuffix, svDirSuffix)),
-            inConfig(Test)(makeSources(nonScalaDirSuffix, svDirSuffix))
+            inConfig(Test)(makeSources(nonScalaDirSuffix, svDirSuffix)),
+            projectDependencies := projectDependenciesTask.value,
           )
           .settings(self.settings)
           .configure(transforms: _*)
@@ -258,6 +259,43 @@ object ProjectMatrix {
       }): _*)
     }
 
+  // backport of https://github.com/sbt/sbt/pull/5767
+  def projectDependenciesTask: Def.Initialize[Task[Seq[ModuleID]]] =
+    Def.task {
+      val orig = projectDependencies.value
+      val sbv = scalaBinaryVersion.value
+      val ref = thisProjectRef.value
+      val data = settingsData.value
+      val deps = buildDependencies.value
+      val sbtV = VersionNumber(sbtVersion.value)
+
+      if (sbtV._1.getOrElse(0L) == 1 && (sbtV._2.getOrElse(0L) < 4)) {
+        deps.classpath(ref) flatMap { dep =>
+          val depProjIdOpt = (dep.project / projectID).get(data)
+          val depSVOpt = (dep.project / scalaVersion).get(data)
+          val depSBVOpt = (dep.project / scalaBinaryVersion).get(data)
+          val depCrossOpt = (dep.project / crossVersion).get(data)
+          (depProjIdOpt, depSVOpt, depSBVOpt, depCrossOpt) match {
+            case (Some(depProjId), Some(depSV), Some(depSBV), Some(depCross)) =>
+              if (sbv == depSBV || depCross != CrossVersion.binary)
+                Some(
+                  depProjId.withConfigurations(dep.configuration).withExplicitArtifacts(Vector.empty)
+                )
+              else if (VirtualAxis.isScala2Scala3Sandwich(sbv, depSBV) && depCross == CrossVersion.binary)
+                Some(
+                  depProjId
+                    .withCrossVersion(CrossVersion.constant(depSBV))
+                    .withConfigurations(dep.configuration)
+                    .withExplicitArtifacts(Vector.empty)
+                )
+              else sys.error(s"scalaBinaryVersion mismatch: expected $sbv but found ${depSBV}")
+            case _ => None
+          }
+        }
+      } else {
+        orig
+      }
+    }
 
     override lazy val componentProjects: Seq[Project] = resolvedMappings.values.toList
 

src/sbt-test/projectMatrix/jvm-sandwich/bar-app/D.scala

@@ -0,0 +1,5 @@
+package example
+
+object D {
+  val x = C.x
+}

src/sbt-test/projectMatrix/jvm-sandwich/bar-core/C.scala

@@ -0,0 +1,5 @@
+package example
+
+object C {
+  val x = 1
+}

src/sbt-test/projectMatrix/jvm-sandwich/baz-app/F.scala

@@ -0,0 +1,5 @@
+package example
+
+object F {
+  val x = E.x
+}

src/sbt-test/projectMatrix/jvm-sandwich/baz-core/E.scala

@@ -0,0 +1,5 @@
+package example
+
+object E {
+  val x = 1
+}

src/sbt-test/projectMatrix/jvm-sandwich/build.sbt

@@ -1,3 +1,5 @@
+lazy val check = taskKey[Unit]("")
+
 val dottyVersion = "0.23.0"
 ThisBuild / resolvers += "scala-integration" at "https://scala-ci.typesafe.com/artifactory/scala-integration/"
 // TODO use 2.13.4 when it's out
@@ -6,12 +8,47 @@ lazy val scala213 = "2.13.4-bin-aeee8f0"
 lazy val fooApp = (projectMatrix in file("foo-app"))
   .dependsOn(fooCore)
   .settings(
-    name := "app",
+    name := "foo app",
   )
   .jvmPlatform(scalaVersions = Seq(dottyVersion))
 
 lazy val fooCore = (projectMatrix in file("foo-core"))
   .settings(
-    name := "core",
+    name := "foo core",
   )
-  .jvmPlatform(scalaVersions = Seq("2.13.3", "2.12.12"))
+  .jvmPlatform(scalaVersions = Seq(scala213, "2.12.12"))
+
+lazy val barApp = (projectMatrix in file("bar-app"))
+  .dependsOn(barCore)
+  .settings(
+    name := "bar app",
+  )
+  .jvmPlatform(scalaVersions = Seq(scala213))
+
+lazy val barCore = (projectMatrix in file("bar-core"))
+  .settings(
+    name := "bar core",
+  )
+  .jvmPlatform(scalaVersions = Seq(dottyVersion))
+
+// choose 2.13 when bazCore offers both 2.13 and Dotty
+lazy val bazApp = (projectMatrix in file("baz-app"))
+  .dependsOn(bazCore)
+  .settings(
+    name := "baz app",
+    check := {
+      val cp = (Compile / fullClasspath).value
+        .map(_.data.getName)
+
+      assert(cp.contains("baz-core_2.13-0.1.0-SNAPSHOT.jar"), s"$cp")
+      assert(!cp.contains("baz-core_0.23-0.1.0-SNAPSHOT.jar"), s"$cp")
+    },
+  )
+  .jvmPlatform(scalaVersions = Seq(scala213))
+
+lazy val bazCore = (projectMatrix in file("baz-core"))
+  .settings(
+    name := "baz core",
+    exportJars := true,
+  )
+  .jvmPlatform(scalaVersions = Seq(scala213, dottyVersion))

src/sbt-test/projectMatrix/jvm-sandwich/foo-app/B.scala

@@ -0,0 +1,5 @@
+package example
+
+object B {
+  val x = A.x
+}

src/sbt-test/projectMatrix/jvm-sandwich/foo-core/A.scala

@@ -0,0 +1,5 @@
+package example
+
+object A {
+  val x = 1
+}

src/sbt-test/projectMatrix/jvm-sandwich/test

@@ -1,2 +1,5 @@
 > fooAppJVM0_23/compile
 
+> barAppJVM2_13/compile
+
+> bazAppJVM2_13/check