Get the build into shape for a Scala module

  - add the scala-modules SBT plugin
  - configure OSGi package export
  - Check that SBT is running on Java8, rather than waiting for
    cryptic build errors.
  - convert `LambdaTest` to a JUnit test.

Author: retronym

README.md

@@ -40,7 +40,7 @@ TODO
 #### Running Examples
 
 ```
-% (export JAVA_HOME=`java_home 1.8`; export PATH=$JAVA_HOME/bin:$PATH; sbt 'test:runMain scala.compat.jdk8.LambdaTest')
+% (export JAVA_HOME=`java_home 1.8`; export PATH=$JAVA_HOME/bin:$PATH; sbt test)
 ```
 
 ### Future work

build.sbt

@@ -1,9 +1,36 @@
-scalaVersion := "2.10.3"
+import com.typesafe.tools.mima.plugin.{MimaPlugin, MimaKeys}
+
+scalaModuleSettings
+
+scalaVersion := "2.10.4"
+
+snapshotScalaBinaryVersion := "2.10.4"
+
+// TODO this project can be cross build against 2.11 and 2.10, express that here.
 
 organization := "org.scala-lang.modules"
 
 name := "scala-compat-jdk8"
 
+// important!! must come here (why?)
+scalaModuleOsgiSettings
+
+OsgiKeys.exportPackage := Seq(s"scala.compat.jdk8.*;version=${version.value}")
+
+libraryDependencies += "junit" % "junit" % "4.11" % "test"
+
+libraryDependencies += "com.novocode" % "junit-interface" % "0.10" % "test"
+
+MimaPlugin.mimaDefaultSettings
+
+MimaKeys.previousArtifact := None
+
+// run mima during tests
+test in Test := {
+  MimaKeys.reportBinaryIssues.value
+  (test in Test).value
+}
+
 sourceGenerators in Compile <+= sourceManaged in Compile map { dir =>
   def write(name: String, content: String) = {
     val f = dir / "java" / "scala" / "compat" / "jdk8" / s"${name}.java"
@@ -21,3 +48,10 @@ sourceGenerators in Test <+= sourceManaged in Test map { dir =>
   }
   Seq(write("TestApi", CodeGen.testApi))
 }
+
+initialize := {
+  val _ = initialize.value
+  val specVersion = sys.props("java.specification.version")
+  if (Set("1.5", "1.6", "1.7") contains specVersion)
+    sys.error("Java 8 or higher is required for this project.")
+}

project/plugins.sbt

@@ -0,0 +1,3 @@
+addSbtPlugin("org.scala-lang.modules" % "scala-module-plugin" % "1.0.2")
+
+addSbtPlugin("com.typesafe" % "sbt-mima-plugin" % "0.1.6")

src/test/java/scala/compat/jdk8/LambdaTest.java

@@ -6,9 +6,11 @@
 import scala.runtime.*;
 import static scala.compat.jdk8.TestAPI.*;
 import static scala.compat.jdk8.JFunction.*;
+import org.junit.Test;
 
 public class LambdaTest {
-    public static void main(String[] args) {
+    @Test
+    public static void lambdaDemo() {
         // Not allowed with Scala 2.10 nor 2.11
         // "incompatible types: Function1 is not a functional interface"
         // scala.Function1<String, String> f = (String s) -> s;