From 7630ed8201969c82a718a6630588fe4b2485f838 Mon Sep 17 00:00:00 2001
From: Arnout Engelen <arnouten@bzzt.net>
Date: Tue, 3 Jul 2018 11:06:04 +0200
Subject: [PATCH] Select most recent jdk

When multiple jdk minor/patch versions are available, select the most
recent one.
---
 .../main/scala/sbt/internal/CrossJava.scala   | 52 ++++++++++++++-----
 .../scala/sbt/internal/CrossJavaTest.scala    | 13 +++++
 2 files changed, 52 insertions(+), 13 deletions(-)
 create mode 100644 main/src/test/scala/sbt/internal/CrossJavaTest.scala

diff --git a/main/src/main/scala/sbt/internal/CrossJava.scala b/main/src/main/scala/sbt/internal/CrossJava.scala
index 9ee668042..91b829261 100644
--- a/main/src/main/scala/sbt/internal/CrossJava.scala
+++ b/main/src/main/scala/sbt/internal/CrossJava.scala
@@ -10,6 +10,7 @@ package internal
 
 import java.io.File
 import scala.collection.immutable.ListMap
+import scala.annotation.tailrec
 import sbt.io.Path
 import sbt.io.syntax._
 import sbt.Cross._
@@ -308,24 +309,47 @@ private[sbt] object CrossJava {
     def javaHomes: Vector[(String, File)]
   }
 
+  // Sort version strings, considering 1.8.0 < 1.8.0_45 < 1.8.0_212
+  @tailrec
+  def versionOrder(left: String, right: String): Boolean = {
+    val Pattern = """.*?([0-9]+)(.*)""".r
+    left match {
+      case Pattern(leftNumber, leftRest) =>
+        right match {
+          case Pattern(rightNumber, rightRest) =>
+            if (Integer.parseInt(leftNumber) < Integer.parseInt(rightNumber)) true
+            else if (Integer.parseInt(leftNumber) > Integer.parseInt(rightNumber)) false
+            else versionOrder(leftRest, rightRest)
+          case _ =>
+            false
+        }
+      case _ =>
+        true
+    }
+  }
+
   object JavaDiscoverConfig {
     val linux = new JavaDiscoverConf {
       val base: File = file("/usr") / "lib" / "jvm"
       val JavaHomeDir = """java-([0-9]+)-.*""".r
       def javaHomes: Vector[(String, File)] =
-        wrapNull(base.list()).collect {
-          case dir @ JavaHomeDir(ver) => JavaVersion(ver).toString -> (base / dir)
-        }
+        wrapNull(base.list())
+          .sortWith(versionOrder)
+          .collect {
+            case dir @ JavaHomeDir(ver) => JavaVersion(ver).toString -> (base / dir)
+          }
     }
 
     val macOS = new JavaDiscoverConf {
       val base: File = file("/Library") / "Java" / "JavaVirtualMachines"
       val JavaHomeDir = """jdk-?(1\.)?([0-9]+).*""".r
       def javaHomes: Vector[(String, File)] =
-        wrapNull(base.list()).collect {
-          case dir @ JavaHomeDir(m, n) =>
-            JavaVersion(nullBlank(m) + n).toString -> (base / dir / "Contents" / "Home")
-        }
+        wrapNull(base.list())
+          .sortWith(versionOrder)
+          .collect {
+            case dir @ JavaHomeDir(m, n) =>
+              JavaVersion(nullBlank(m) + n).toString -> (base / dir / "Contents" / "Home")
+          }
     }
 
     // See https://github.com/shyiko/jabba
@@ -333,12 +357,14 @@ private[sbt] object CrossJava {
       val base: File = Path.userHome / ".jabba" / "jdk"
       val JavaHomeDir = """([\w\-]+)\@(1\.)?([0-9]+).*""".r
       def javaHomes: Vector[(String, File)] =
-        wrapNull(base.list()).collect {
-          case dir @ JavaHomeDir(vendor, m, n) =>
-            val v = JavaVersion(nullBlank(m) + n).withVendor(vendor).toString
-            if ((base / dir / "Contents" / "Home").exists) v -> (base / dir / "Contents" / "Home")
-            else v -> (base / dir)
-        }
+        wrapNull(base.list())
+          .sortWith(versionOrder)
+          .collect {
+            case dir @ JavaHomeDir(vendor, m, n) =>
+              val v = JavaVersion(nullBlank(m) + n).withVendor(vendor).toString
+              if ((base / dir / "Contents" / "Home").exists) v -> (base / dir / "Contents" / "Home")
+              else v -> (base / dir)
+          }
     }
   }
 
diff --git a/main/src/test/scala/sbt/internal/CrossJavaTest.scala b/main/src/test/scala/sbt/internal/CrossJavaTest.scala
new file mode 100644
index 000000000..8c363391b
--- /dev/null
+++ b/main/src/test/scala/sbt/internal/CrossJavaTest.scala
@@ -0,0 +1,13 @@
+package sbt.internal
+
+import org.specs2.mutable.Specification
+
+class CrossJavaTest extends Specification {
+  "The Java home selector" should {
+    "select the most recent" in {
+      List("jdk1.8.0.jdk", "jdk1.8.0_121.jdk", "jdk1.8.0_45.jdk")
+        .sortWith(CrossJava.versionOrder)
+        .last must be equalTo ("jdk1.8.0_121.jdk")
+    }
+  }
+}