Discovery of java homes

main/src/main/contraband-scala/sbt/JavaVersion.scala

@@ -0,0 +1,40 @@
+/**
+ * This code is generated using [[http://www.scala-sbt.org/contraband/ sbt-contraband]].
+ */
+
+// DO NOT EDIT MANUALLY
+package sbt
+final class JavaVersion private (
+  val vendor: Option[String],
+  val version: String) extends Serializable {
+  
+  
+  
+  override def equals(o: Any): Boolean = o match {
+    case x: JavaVersion => (this.vendor == x.vendor) && (this.version == x.version)
+    case _ => false
+  }
+  override def hashCode: Int = {
+    37 * (37 * (37 * (17 + "sbt.JavaVersion".##) + vendor.##) + version.##)
+  }
+  override def toString: String = {
+    "JavaVersion(" + vendor + ", " + version + ")"
+  }
+  private[this] def copy(vendor: Option[String] = vendor, version: String = version): JavaVersion = {
+    new JavaVersion(vendor, version)
+  }
+  def withVendor(vendor: Option[String]): JavaVersion = {
+    copy(vendor = vendor)
+  }
+  def withVendor(vendor: String): JavaVersion = {
+    copy(vendor = Option(vendor))
+  }
+  def withVersion(version: String): JavaVersion = {
+    copy(version = version)
+  }
+}
+object JavaVersion {
+  def apply(version: String): JavaVersion = new JavaVersion(None, version)
+  def apply(vendor: Option[String], version: String): JavaVersion = new JavaVersion(vendor, version)
+  def apply(vendor: String, version: String): JavaVersion = new JavaVersion(Option(vendor), version)
+}

main/src/main/contraband/main.contra

@@ -17,3 +17,9 @@ enum PluginTrigger {
   AllRequirements
   NoTrigger
 }
+
+type JavaVersion {
+  vendor: String
+  version: String!
+  #xcompanion def apply(version: String): JavaVersion = new JavaVersion(None, version)
+}

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

@@ -69,6 +69,7 @@ import sbt.librarymanagement.syntax._
 import sbt.util.InterfaceUtil.{ toJavaFunction => f1 }
 import sbt.util._
 import sbt.util.CacheImplicits._
+import scala.collection.immutable.ListMap
 import scala.concurrent.duration.FiniteDuration
 import scala.util.control.NonFatal
 import scala.xml.NodeSeq
@@ -159,6 +160,9 @@ object Defaults extends BuildCommon {
       scalaHome :== None,
       apiURL := None,
       javaHome :== None,
+      discoveredJavaHomes := sbt.internal.CrossJava.discoverJavaHomes,
+      javaHomes :== ListMap.empty,
+      fullJavaHomes := discoveredJavaHomes.value ++ javaHomes.value,
       testForkedParallel :== false,
       javaOptions :== Nil,
       sbtPlugin :== false,

main/src/main/scala/sbt/Keys.scala

@@ -271,6 +271,10 @@ object Keys {
   val outputStrategy = settingKey[Option[sbt.OutputStrategy]]("Selects how to log output when running a main class.").withRank(DSetting)
   val connectInput = settingKey[Boolean]("If true, connects standard input when running a main class forked.").withRank(CSetting)
   val javaHome = settingKey[Option[File]]("Selects the Java installation used for compiling and forking.  If None, uses the Java installation running the build.").withRank(ASetting)
+  val discoveredJavaHomes = settingKey[Map[JavaVersion, File]]("Discovered Java home directories")
+  val javaHomes = settingKey[Map[JavaVersion, File]]("The user-defined additional Java home directories")
+  val fullJavaHomes = taskKey[Map[JavaVersion, File]]("Combines discoveredJavaHomes and custom javaHomes.").withRank(CTask)
+
   val javaOptions = taskKey[Seq[String]]("Options passed to a new JVM when forking.").withRank(BPlusTask)
   val envVars = taskKey[Map[String, String]]("Environment variables used when forking a new JVM").withRank(BTask)
 

main/src/main/scala/sbt/internal/CrossJava.scala

@@ -0,0 +1,50 @@
+/*
+ * sbt
+ * Copyright 2011 - 2017, Lightbend, Inc.
+ * Copyright 2008 - 2010, Mark Harrah
+ * Licensed under BSD-3-Clause license (see LICENSE)
+ */
+
+package sbt
+package internal
+
+import java.io.File
+import scala.collection.immutable.ListMap
+import sbt.io.IO
+import sbt.io.syntax._
+
+private[sbt] object CrossJava {
+  def discoverJavaHomes: ListMap[JavaVersion, File] = {
+    val configs = Vector(JavaDiscoverConfig.linux, JavaDiscoverConfig.macOS)
+    ListMap(configs flatMap { _.javaHomes }: _*)
+  }
+
+  sealed trait JavaDiscoverConf {
+    def javaHomes: Vector[(JavaVersion, File)]
+  }
+
+  object JavaDiscoverConfig {
+    val linux = new JavaDiscoverConf {
+      val base: File = file("/usr") / "lib" / "jvm"
+      val JavaHomeDir = """java-([0-9]+)-.*""".r
+      def javaHomes: Vector[(JavaVersion, File)] =
+        wrapNull(base.list()).collect {
+          case dir @ JavaHomeDir(ver) => JavaVersion(ver) -> (base / dir)
+        }
+    }
+
+    val macOS = new JavaDiscoverConf {
+      val base: File = file("/Library") / "Java" / "JavaVirtualMachines"
+      val JavaHomeDir = """jdk-?(1\.)?([0-9]+).*""".r
+      def javaHomes: Vector[(JavaVersion, File)] =
+        wrapNull(base.list()).collect {
+          case dir @ JavaHomeDir(m, n) =>
+            JavaVersion(n) -> (base / dir / "Contents" / "Home")
+        }
+    }
+  }
+
+  def wrapNull(a: Array[String]): Vector[String] =
+    if (a eq null) Vector()
+    else a.toVector
+}

sbt/src/sbt-test/java/home-discovery/build.sbt

@@ -0,0 +1,5 @@
+Global / javaHomes += JavaVersion("6") -> file("/good/old/times/java-6")
+
+TaskKey[Unit]("check") := {
+  assert(fullJavaHomes.value(JavaVersion("6")).getAbsolutePath.contains("java-6"))
+}

sbt/src/sbt-test/java/home-discovery/test

@@ -0,0 +1 @@
+> check