From b0ee80e34ee09519ffa41267093ca2126737a949 Mon Sep 17 00:00:00 2001
From: Adrien Piquerez <adrien.piquerez@gmail.com>
Date: Thu, 1 Apr 2021 10:22:12 +0200
Subject: [PATCH 1/2] Use full Scala 3 version in crossTarget

---
 main/src/main/scala/sbt/Defaults.scala | 20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/main/src/main/scala/sbt/Defaults.scala b/main/src/main/scala/sbt/Defaults.scala
index 5a491f973..e6fa6262c 100644
--- a/main/src/main/scala/sbt/Defaults.scala
+++ b/main/src/main/scala/sbt/Defaults.scala
@@ -692,6 +692,7 @@ object Defaults extends BuildCommon {
     crossSbtVersions := Vector((pluginCrossBuild / sbtVersion).value),
     crossTarget := makeCrossTarget(
       target.value,
+      scalaVersion.value,
       scalaBinaryVersion.value,
       (pluginCrossBuild / sbtBinaryVersion).value,
       sbtPlugin.value,
@@ -772,8 +773,23 @@ object Defaults extends BuildCommon {
     else Vector()
   }
 
-  def makeCrossTarget(t: File, sv: String, sbtv: String, plugin: Boolean, cross: Boolean): File = {
-    val scalaBase = if (cross) t / ("scala-" + sv) else t
+  @deprecated("Use constructor with scalaVersion and scalaBinaryVersion", "1.5.0")
+  def makeCrossTarget(t: File, bv: String, sbtv: String, plugin: Boolean, cross: Boolean): File = {
+    val scalaBase = if (cross) t / ("scala-" + bv) else t
+    if (plugin) scalaBase / ("sbt-" + sbtv) else scalaBase
+  }
+
+  def makeCrossTarget(
+      t: File,
+      scalaVersion: String,
+      scalaBinaryVersion: String,
+      sbtv: String,
+      plugin: Boolean,
+      cross: Boolean
+  ): File = {
+    val scalaSuffix =
+      if (ScalaArtifacts.isScala3(scalaVersion)) scalaVersion else scalaBinaryVersion
+    val scalaBase = if (cross) t / ("scala-" + scalaSuffix) else t
     if (plugin) scalaBase / ("sbt-" + sbtv) else scalaBase
   }
 

From 09dd3b09f4b8fdcca6dcc309f4307d6620a6b5ff Mon Sep 17 00:00:00 2001
From: Adrien Piquerez <adrien.piquerez@gmail.com>
Date: Thu, 1 Apr 2021 13:56:51 +0200
Subject: [PATCH 2/2] Add test for Scala 3 cross-target

---
 sbt/src/sbt-test/project/scala3-cross-target/build.sbt     | 3 +++
 .../project/scala3-cross-target/src/main/scala/Foo.scala   | 1 +
 sbt/src/sbt-test/project/scala3-cross-target/test          | 7 +++++++
 3 files changed, 11 insertions(+)
 create mode 100644 sbt/src/sbt-test/project/scala3-cross-target/build.sbt
 create mode 100644 sbt/src/sbt-test/project/scala3-cross-target/src/main/scala/Foo.scala
 create mode 100644 sbt/src/sbt-test/project/scala3-cross-target/test

diff --git a/sbt/src/sbt-test/project/scala3-cross-target/build.sbt b/sbt/src/sbt-test/project/scala3-cross-target/build.sbt
new file mode 100644
index 000000000..d87ccac1b
--- /dev/null
+++ b/sbt/src/sbt-test/project/scala3-cross-target/build.sbt
@@ -0,0 +1,3 @@
+scalaVersion := "3.0.0-RC2-bin-20210328-cca5f8f-NIGHTLY"
+name := "foo"
+version := "1.0.0"
diff --git a/sbt/src/sbt-test/project/scala3-cross-target/src/main/scala/Foo.scala b/sbt/src/sbt-test/project/scala3-cross-target/src/main/scala/Foo.scala
new file mode 100644
index 000000000..d37c10456
--- /dev/null
+++ b/sbt/src/sbt-test/project/scala3-cross-target/src/main/scala/Foo.scala
@@ -0,0 +1 @@
+object Foo
\ No newline at end of file
diff --git a/sbt/src/sbt-test/project/scala3-cross-target/test b/sbt/src/sbt-test/project/scala3-cross-target/test
new file mode 100644
index 000000000..ff09e0f19
--- /dev/null
+++ b/sbt/src/sbt-test/project/scala3-cross-target/test
@@ -0,0 +1,7 @@
+> compile
+
+$ exists target/scala-3.0.0-RC2-bin-20210328-cca5f8f-NIGHTLY/classes/Foo$.class
+
+> package
+
+$ exists target/scala-3.0.0-RC2-bin-20210328-cca5f8f-NIGHTLY/foo_3.0.0-RC2-1.0.0.jar