Convert to AutoPlugin, apply Scala version settings to the build

Make sure to set `crossScalaVersions` / `scalaVersion` (using `scalaVersionsByJvm`) in the
build, not only the project where `scalaModuleSettings` is referenced.

Author: lrytz

README.md

@@ -13,16 +13,19 @@ addSbtPlugin("org.scala-lang.modules" % "scala-module-plugin" % "1.0.6")
 Then, in your `build.sbt` add:
 
 ```
-scalaModuleSettings
+import ScalaModulePlugin._
+
+scalaModuleSettings // in a multi-project build, you might want to apply these settings only to the
+                    // main project (example: scala-parallel-collections)
 
 name         := "<module name>"
 repoName     := "<GitHub repo name>" // the repo under github.com/scala/, only required if different from name
 organization := "<org>"              // only required if different from "org.scala-lang.modules"
 version      := "<module version>"
 
-// The plugin uses `scalaVersionsByJvm` to set `crossScalaVersions` according to the JVM major version.
-// The `scalaVersion` is set to `crossScalaVersions.value.head`.
-scalaVersionsByJvm := {
+// The plugin uses `scalaVersionsByJvm` to set `crossScalaVersions in ThisBuild` according to the JVM major version.
+// The `scalaVersion in ThisBuild` is set to `crossScalaVersions.value.head`.
+scalaVersionsByJvm in ThisBuild := {
   val v211 = "2.11.11"
   val v212 = "2.12.2"
   val v213 = "2.13.0-M1"
@@ -32,8 +35,7 @@ scalaVersionsByJvm := {
     6 -> List(v211 -> true),
     7 -> List(v211 -> false),
     8 -> List(v212 -> true, v213 -> true, v211 -> false),
-    9 -> List(v212, v213, v211).map(_ -> false)
-  )
+    9 -> List(v212, v213, v211).map(_ -> false))
 }
 
 mimaPreviousVersion := Some("1.0.3") // enables MiMa (`None` by default, which disables it)
@@ -43,6 +45,18 @@ OsgiKeys.exportPackage := Seq(s"<exported package>;version=${version.value}")
 // Other settings
 ```
 
+These additional settings are enabled by `scalaModuleSettings`:
+  - `scalacOptions in (Compile, compile) ++= Seq("-feature", "-deprecation", "-unchecked", "-Xlint")`
+  - A `projectName.properties` file is generated and packaged
+  - `fork in Test := true` to work around some classpath clashes with scala-xml
+  - `publishTo` sonatype, credentials file expected in `~/.ivy2/.credentials`
+  - POM and OSGi metadata
+
+The following settings are also available:
+  - `enableOptimizer` adds `-opt:l:classpath` or `-optimize` to `scalacOptions in (Compile, compile)`,
+    depending on the Scala version
+  - `disablePublishing` is useful for multi-project builds for projects that should not be published
+
 ## Cutting a new release
 
 - Sign in to Bintray (https://bintray.com/login) or create an "Open Source" account (https://bintray.com/signup/oss)

project/build.properties

@@ -1 +1 @@
-sbt.version=0.13.13
+sbt.version=0.13.15

src/main/scala/ScalaModulePlugin.scala

@@ -3,56 +3,85 @@ import Keys._
 import com.typesafe.sbt.osgi.{OsgiKeys, SbtOsgi}
 import com.typesafe.tools.mima.plugin.{MimaPlugin, MimaKeys}, MimaKeys._
 
-object ScalaModulePlugin extends Plugin {
-  val repoName                   = settingKey[String]("The name of the repository under github.com/scala/.")
-  val mimaPreviousVersion        = settingKey[Option[String]]("The version of this module to compare against when running MiMa.")
-  val scalaVersionsByJvm         = settingKey[Map[Int, List[(String, Boolean)]]]("For a Java major version (6, 8, 9), a list of Scala version and a flag indicating whether to use this combination for publishing.")
+object ScalaModulePlugin extends AutoPlugin {
+  val repoName            = settingKey[String]("The name of the repository under github.com/scala/.")
+  val mimaPreviousVersion = settingKey[Option[String]]("The version of this module to compare against when running MiMa.")
+  val scalaVersionsByJvm  = settingKey[Map[Int, List[(String, Boolean)]]]("For a Java major version (6, 8, 9), a list of a Scala version and a flag indicating whether to use this combination for publishing.")
 
-  private val canRunMima         = taskKey[Boolean]("Decides if MiMa should run.")
-  private val runMimaIfEnabled   = taskKey[Unit]("Run MiMa if mimaPreviousVersion and the module can be resolved against the current scalaBinaryVersion.")
+  // Settings applied to the entire build when the plugin is loaded.
 
-  lazy val scalaModuleSettings: Seq[Setting[_]] = Seq(
-    repoName            := name.value,
-
-    mimaPreviousVersion := None,
+  override def trigger = allRequirements
 
-    scalaVersionsByJvm  := Map.empty,
+  override def buildSettings: Seq[Setting[_]] = Seq(
+    scalaVersionsByJvm := Map.empty,
 
-    crossScalaVersions  := {
+    crossScalaVersions in ThisBuild := {
       val OneDot = """1\.(\d).*""".r // 1.6, 1.8
       val Maj    = """(\d+).*""".r   // 9
       val javaVersion = System.getProperty("java.version") match {
         case OneDot(n) => n.toInt
         case Maj(n)    => n.toInt
         case v         => throw new RuntimeException(s"Unknown Java version: $v")
       }
-      val isTravisPublishing = Option(System.getenv("TRAVIS_TAG")).getOrElse("").trim.nonEmpty
-      val scalaVersions = scalaVersionsByJvm.value.getOrElse(javaVersion, Nil) collect {
+
+      val isTravis = Option(System.getenv("TRAVIS")).exists(_ == "true") // `contains` doesn't exist in Scala 2.10
+      val isTravisPublishing = Option(System.getenv("TRAVIS_TAG")).exists(_.trim.nonEmpty)
+
+      val byJvm = scalaVersionsByJvm.value
+      if (byJvm.isEmpty)
+        throw new RuntimeException(s"Make sure to define `scalaVersionsByJvm in ThisBuild` in `build.sbt` in the root project, using the `ThisBuild` scope.")
+
+      val scalaVersions = byJvm.getOrElse(javaVersion, Nil) collect {
         case (v, publish) if !isTravisPublishing || publish => v
       }
       if (scalaVersions.isEmpty) {
-        if (isTravisPublishing) {
+        if (isTravis) {
           sLog.value.warn(s"No Scala version in `scalaVersionsByJvm` in build.sbt needs to be released on Java major version $javaVersion.")
           // Exit successfully, don't fail the (travis) build. This happens for example if `openjdk7`
           // is part of the travis configuration for testing, but it's not used for releasing against
           // any Scala version.
           System.exit(0)
         } else
-          throw new RuntimeException(s"No Scala version for Java major version $javaVersion. Adjust `scalaVersionsByJvm` in build.sbt.")
+          throw new RuntimeException(s"No Scala version for Java major version $javaVersion. Change your Java version or adjust `scalaVersionsByJvm` in build.sbt.")
       }
       scalaVersions
     },
 
-    scalaVersion       := crossScalaVersions.value.head,
+    scalaVersion in ThisBuild := crossScalaVersions.value.head
+  )
+
+  /**
+   * Enable `-opt:l:classpath` or `-optimize`, depending on the scala version.
+   */
+  lazy val enableOptimizer: Setting[_] = scalacOptions in (Compile, compile) += {
+    val ScalaMaj = """2\.(\d+)\..*""".r
+    val ScalaMaj(scalaMaj) = scalaVersion.value
+    if (scalaMaj.toInt >= 12) "-opt:l:classpath" else "-optimize"
+  }
+
+  /**
+   * Practical for multi-project builds.
+   */
+  lazy val disablePublishing: Seq[Setting[_]] = Seq(
+    publishArtifact := false,
+    // The above is enough for Maven repos but it doesn't prevent publishing of ivy.xml files
+    publish := {},
+    publishLocal := {},
+    publishTo := Some(Resolver.file("devnull", file("/dev/null")))
+  )
+
+  /**
+   * To be included in the main sbt project of a Scala module.
+   */
+  lazy val scalaModuleSettings: Seq[Setting[_]] = Seq(
+    repoName := name.value,
 
-    organization        := "org.scala-lang.modules",
+    mimaPreviousVersion := None,
 
-    // so we don't have to wait for sonatype to synch to maven central when deploying a new module
-    resolvers += Resolver.sonatypeRepo("releases"),
+    organization := "org.scala-lang.modules",
 
     // don't use for doc scope, scaladoc warnings are not to be reckoned with
-    // TODO: turn on for nightlies, but don't enable for PR validation... "-Xfatal-warnings"
-    scalacOptions in compile ++= Seq("-optimize", "-feature", "-deprecation", "-unchecked", "-Xlint"),
+    scalacOptions in (Compile, compile) ++= Seq("-feature", "-deprecation", "-unchecked", "-Xlint"),
 
     // Generate $name.properties to store our version as well as the scala version used to build
     resourceGenerators in Compile += Def.task {
@@ -76,8 +105,6 @@ object ScalaModulePlugin extends Plugin {
     // alternatively, manage the scala instance as shown at the end of this file (commented)
     fork in Test := true,
 
-    publishArtifact in Test := false,
-
     // maven publishing
     publishTo := Some(
       if (version.value.trim.endsWith("SNAPSHOT")) Resolver.sonatypeRepo("snapshots")
@@ -114,7 +141,7 @@ object ScalaModulePlugin extends Plugin {
   ) ++ mimaSettings ++ scalaModuleOsgiSettings
 
   // adapted from https://github.com/typesafehub/migration-manager/blob/0.1.6/sbtplugin/src/main/scala/com/typesafe/tools/mima/plugin/SbtMima.scala#L69
-  def artifactExists(organization: String, name: String, scalaBinaryVersion: String, version: String, ivy: IvySbt, s: TaskStreams): Boolean = {
+  private def artifactExists(organization: String, name: String, scalaBinaryVersion: String, version: String, ivy: IvySbt, s: TaskStreams): Boolean = {
     val moduleId = new ModuleID(organization, s"${name}_$scalaBinaryVersion", version)
     val moduleSettings = InlineConfiguration(
       "dummy" % "test" % "version",
@@ -135,7 +162,11 @@ object ScalaModulePlugin extends Plugin {
     }
   }
 
-  lazy val mimaSettings: Seq[Setting[_]] = MimaPlugin.mimaDefaultSettings ++ Seq(
+  // Internal task keys for the MiMa settings
+  private val canRunMima       = taskKey[Boolean]("Decides if MiMa should run.")
+  private val runMimaIfEnabled = taskKey[Unit]("Run MiMa if mimaPreviousVersion and the module can be resolved against the current scalaBinaryVersion.")
+
+  private lazy val mimaSettings: Seq[Setting[_]] = MimaPlugin.mimaDefaultSettings ++ Seq(
     // manual cross-versioning because https://github.com/typesafehub/migration-manager/issues/62
     mimaPreviousArtifacts := Set(organization.value % s"${name.value}_${scalaBinaryVersion.value}" % mimaPreviousVersion.value.getOrElse("dummy")),
 
@@ -165,9 +196,9 @@ object ScalaModulePlugin extends Plugin {
   )
 
   // a setting-transform to turn the regular version into something osgi can deal with
-  val osgiVersion = version(_.replace('-', '.'))
+  private val osgiVersion = version(_.replace('-', '.'))
 
-  lazy val scalaModuleOsgiSettings = SbtOsgi.osgiSettings ++ Seq(
+  private lazy val scalaModuleOsgiSettings = SbtOsgi.osgiSettings ++ Seq(
     OsgiKeys.bundleSymbolicName  := s"${organization.value}.${name.value}",
     OsgiKeys.bundleVersion       := osgiVersion.value,