Add some helpers to simplify cross-version/cross-platform modules

example/web/5-webapp-scalajs-shared/build.sc

@@ -32,8 +32,7 @@ object app extends RootModule with AppScalaModule{
   }
 
   object shared extends Module{
-    trait SharedModule extends AppScalaModule{
-      def millSourcePath = super.millSourcePath / os.up
+    trait SharedModule extends AppScalaModule with PlatformScalaModule {
 
       def ivyDeps = Agg(
         ivy"com.lihaoyi::scalatags::0.12.0",

example/web/6-cross-platform-publishing/build.sc

@@ -1,13 +1,8 @@
 import mill._, scalalib._, scalajslib._, publish._
 
 object wrapper extends Cross[WrapperModule]("2.13.10", "3.2.2")
-class WrapperModule(val crossScalaVersion: String) extends Module {
-
-  trait MyModule extends CrossScalaModule with PublishModule {
-    def artifactName = millModuleSegments.parts.dropRight(1).last
-
-    def crossScalaVersion = WrapperModule.this.crossScalaVersion
-    def millSourcePath = super.millSourcePath / os.up
+class WrapperModule(val crossScalaVersion: String) extends CrossScalaModule.Wrapper {
+  trait MyScalaModule extends CrossScalaModule with PlatformScalaModule with PublishModule {
     def publishVersion = "0.0.1"
 
     def pomSettings = PomSettings(
@@ -25,23 +20,14 @@ class WrapperModule(val crossScalaVersion: String) extends Module {
       def ivyDeps = Agg(ivy"com.lihaoyi::utest::0.7.11")
       def testFramework = "utest.runner.Framework"
     }
-
-    def sources = T.sources {
-      val platform = millModuleSegments.parts.last
-      super.sources().flatMap(source =>
-        Seq(
-          source,
-          PathRef(source.path / os.up / s"${source.path.last}-${platform}")
-        )
-      )
-    }
   }
-  trait MyScalaJSModule extends MyModule with ScalaJSModule {
+
+  trait MyScalaJSModule extends MyScalaModule with ScalaJSModule {
     def scalaJSVersion = "1.13.0"
   }
 
   object foo extends Module{
-    object jvm extends MyModule{
+    object jvm extends MyScalaModule{
       def moduleDeps = Seq(bar.jvm)
       def ivyDeps = super.ivyDeps() ++ Agg(ivy"com.lihaoyi::upickle::3.0.0")
     }
@@ -51,7 +37,7 @@ class WrapperModule(val crossScalaVersion: String) extends Module {
   }
 
   object bar extends Module{
-    object jvm extends MyModule
+    object jvm extends MyScalaModule
     object js extends MyScalaJSModule
   }
 }
@@ -93,12 +79,12 @@ Parsing JSON with js.JSON.parse
 Foo.main: Set(<p>i</p>, <p>cow</p>, <p>me</p>)
 
 > ./mill __.publishLocal
-Publishing Artifact(com.lihaoyi,bar_sjs1_2.13,0.0.1) to ivy repo
-Publishing Artifact(com.lihaoyi,bar_2.13,0.0.1) to ivy repo
-Publishing Artifact(com.lihaoyi,foo_sjs1_2.13,0.0.1) to ivy repo
-Publishing Artifact(com.lihaoyi,foo_2.13,0.0.1) to ivy repo
-Publishing Artifact(com.lihaoyi,bar_sjs1_3,0.0.1) to ivy repo
-Publishing Artifact(com.lihaoyi,bar_3,0.0.1) to ivy repo
-Publishing Artifact(com.lihaoyi,foo_sjs1_3,0.0.1) to ivy repo
-Publishing Artifact(com.lihaoyi,foo_3,0.0.1) to ivy repo
-*/
+Publishing Artifact(com.lihaoyi,wrapper-bar_sjs1_2.13,0.0.1) to ivy repo
+Publishing Artifact(com.lihaoyi,wrapper-bar_2.13,0.0.1) to ivy repo
+Publishing Artifact(com.lihaoyi,wrapper-foo_sjs1_2.13,0.0.1) to ivy repo
+Publishing Artifact(com.lihaoyi,wrapper-foo_2.13,0.0.1) to ivy repo
+Publishing Artifact(com.lihaoyi,wrapper-bar_sjs1_3,0.0.1) to ivy repo
+Publishing Artifact(com.lihaoyi,wrapper-bar_3,0.0.1) to ivy repo
+Publishing Artifact(com.lihaoyi,wrapper-foo_sjs1_3,0.0.1) to ivy repo
+Publishing Artifact(com.lihaoyi,wrapper-foo_3,0.0.1) to ivy repo
+*/

scalalib/src/mill/scalalib/CrossModuleBase.scala

@@ -12,7 +12,8 @@ trait CrossModuleBase extends ScalaModule {
   protected def scalaVersionDirectoryNames: Seq[String] =
     ZincWorkerUtil.matchingVersions(crossScalaVersion)
 
-  override def artifactName: T[String] = millModuleSegments.parts.init.mkString("-")
+  protected def wrapperSegments =  millModuleSegments.parts
+  override def artifactNameParts = super.artifactNameParts().patch(wrapperSegments.size - 1, Nil, 1)
   implicit def crossSbtModuleResolver: Resolver[CrossModuleBase] =
     new Resolver[CrossModuleBase] {
       def resolve[V <: CrossModuleBase](c: Cross[V]): V = {

scalalib/src/mill/scalalib/CrossScalaModule.scala

@@ -4,9 +4,10 @@ import mill.api.PathRef
 import mill.T
 
 /**
- * A [[ScalaModule]] with is suited to be used with [[mill.define.Cross]].
- * It supports additional source directories with the scala version pattern as suffix (`src-{scalaversionprefix}`),
- * e.g.
+ * A [[ScalaModule]] which is suited to be used with [[mill.define.Cross]].
+ * It supports additional source directories with the scala version pattern
+ * as suffix (`src-{scalaversionprefix}`), e.g.
+ *
  * - src
  * - src-2.11
  * - src-2.12.3
@@ -25,3 +26,19 @@ trait CrossScalaModule extends ScalaModule with CrossModuleBase { outer =>
   }
   trait Tests extends CrossScalaModuleTests
 }
+
+object CrossScalaModule{
+  /**
+   * Used with a [[mill.define.Cross]] when you want [[CrossScalaModule]]'s
+   * nested within it
+   */
+  trait Wrapper extends mill.Module {
+    def crossScalaVersion: String
+    private def wrapperSegments0 = millModuleSegments.parts
+    trait CrossScalaModule extends mill.scalalib.CrossScalaModule {
+      override def wrapperSegments = wrapperSegments0
+      def crossScalaVersion = Wrapper.this.crossScalaVersion
+
+    }
+  }
+}

scalalib/src/mill/scalalib/JavaModule.scala

@@ -832,7 +832,9 @@ trait JavaModule
    * For example, by default a scala module foo.baz might be published as foo-baz_2.12 and a java module would be foo-baz.
    * Setting this to baz would result in a scala artifact baz_2.12 or a java artifact baz.
    */
-  def artifactName: T[String] = millModuleSegments.parts.mkString("-")
+  def artifactName: T[String] = artifactNameParts().mkString("-")
+
+  def artifactNameParts: T[Seq[String]] = millModuleSegments.parts
 
   /**
    * The exact id of the artifact to be published. You probably don't want to override this.

scalalib/src/mill/scalalib/PlatformScalaModule.scala

@@ -0,0 +1,29 @@
+package mill.scalalib
+import mill._
+
+/**
+ * A [[ScalaModule]] intended for defining `.jvm`/`.js`/`.native` submodules
+ * It supports additional source directories per platform, e.g. `src-jvm/` or
+ * `src-js/` and can be used inside a [[CrossScalaModule.Wrapper]], to get one
+ * source folder per platform per version e.g. `src-2.12-jvm/`.
+ *
+ * Adjusts the [[millSourcePath]] and [[artifactNameParts]] to ignore the last
+ * path segment, which is assumed to be the name of the platform the module is
+ * built against and not something that should affect the filesystem path or
+ * artifact name
+ */
+trait PlatformScalaModule extends ScalaModule{
+  override def millSourcePath = super.millSourcePath / os.up
+
+  override def sources = T.sources {
+    val platform = millModuleSegments.parts.last
+    super.sources().flatMap(source =>
+      Seq(
+        source,
+        PathRef(source.path / os.up / s"${source.path.last}-${platform}")
+      )
+    )
+  }
+
+  override def artifactNameParts = super.artifactNameParts().dropRight(1)
+}