Merge pull request #270 from xuwei-k/Java9

add Java 9 test in travis-ci

.travis.yml

@@ -19,4 +19,23 @@ matrix:
   include:
     - jdk: oraclejdk8
       scala: 2.12.1
-      script: sbt ++${TRAVIS_SCALA_VERSION} test
+      script: sbt ++${TRAVIS_SCALA_VERSION} test
+    - dist: trusty
+      group: edge
+      sudo: required
+      scala: 2.12.1
+      jdk: oraclejdk9
+      script:
+      # https://github.com/sbt/sbt/pull/2951
+      - git clone https://github.com/retronym/java9-rt-export
+      - cd java9-rt-export/
+      - git checkout 1019a2873d057dd7214f4135e84283695728395d
+      - jdk_switcher use oraclejdk8
+      - sbt package
+      - jdk_switcher use oraclejdk9
+      - mkdir -p $HOME/.sbt/0.13/java9-rt-ext; java -jar target/java9-rt-export-*.jar $HOME/.sbt/0.13/java9-rt-ext/rt.jar
+      - jar tf $HOME/.sbt/0.13/java9-rt-ext/rt.jar | grep java/lang/Object
+      - cd ..
+      - echo "sbt.version=0.13.14-RC1" > project/build.properties
+      - wget https://raw.githubusercontent.com/paulp/sbt-extras/9ade5fa54914ca8aded44105bf4b9a60966f3ccd/sbt && chmod +x ./sbt
+      - ./sbt -Dscala.ext.dirs=$HOME/.sbt/0.13/java9-rt-ext ++$TRAVIS_SCALA_VERSION test

project/build.scala

@@ -7,6 +7,7 @@ import sbtrelease.ReleasePlugin.autoImport._
 import com.typesafe.tools.mima.plugin.MimaPlugin._
 import com.typesafe.tools.mima.plugin.MimaKeys._
 import org.scalajs.sbtplugin.cross.{ CrossProject, CrossType }
+import org.scalajs.sbtplugin.ScalaJSPlugin.autoImport.scalaJSOptimizerOptions
 
 object build {
   type Sett = Def.Setting[_]
@@ -78,6 +79,16 @@ object build {
       .settings(commonSettings)
       .jvmSettings(jvmSettings)
       .jsSettings(
+        scalaJSOptimizerOptions ~= { options =>
+          // https://github.com/scala-js/scala-js/issues/2798
+          try {
+            scala.util.Properties.isJavaAtLeast("1.8")
+            options
+          } catch {
+            case _: NumberFormatException =>
+              options.withParallel(false)
+          }
+        },
         scalacOptions += {
           val a = (baseDirectory in LocalRootProject).value.toURI.toString
           val g = "https://raw.githubusercontent.com/argonaut-io/argonaut/" + tagOrHash.value