Updates continuations option tests for 2.11

In Scala 2.11, the continuation plugin is no more enabled by default when
available.
Two main changes:
- forces enable the continuation plugin when running the tests on Scala 2.11
- modifies the tests to use the project specific preferences, to avoid side effects
of the configuration changes needed for the tests.

org.scala-ide.sdt.core.tests/src/scala/tools/eclipse/TestUtil.scala

@@ -0,0 +1,11 @@
+package scala.tools.eclipse
+
+import org.osgi.framework.Version
+
+object TestUtil {
+
+  def installedScalaVersionGreaterOrEqualsTo(version: Version): Boolean = {
+    ScalaPlugin.plugin.scalaLibBundle.getVersion().compareTo(version) >= 0
+  }
+
+}

org.scala-ide.sdt.core.tests/src/scala/tools/eclipse/compiler/settings/ContinuationPluginSettingsTest.scala

@@ -8,46 +8,83 @@ import java.io.File
 import org.junit.Ignore
 import org.eclipse.core.resources.IncrementalProjectBuilder
 import org.eclipse.core.runtime.NullProgressMonitor
+import org.osgi.framework.Version
+import org.junit.AfterClass
 
 object ContinuationPluginSettingsTest {
   private val simulator = new EclipseUserSimulator
   lazy val projectName = "test_settings"
-  lazy val project = simulator.createProjectInWorkspace(projectName, false)
+  lazy val project = {
+    val p =simulator.createProjectInWorkspace(projectName, false)
+    val prefs = p.projectSpecificStorage
+    prefs.setValue(SettingConverterUtil.USE_PROJECT_SETTINGS_PREFERENCE, true)
+    prefs.save()
+    p
+  }
+
+  private def setPrefToDefault(key: String) {
+    val prefs = project.projectSpecificStorage
+    prefs.setToDefault(key)
+    prefs.save()
+  }
+
+  private def setPrefValue(key: String, value: String) {
+    val prefs = project.projectSpecificStorage
+    prefs.setValue(key, value)
+    prefs.save()
+  }
+
+  private def setPrefValue(key: String, value: Boolean) {
+    val prefs = project.projectSpecificStorage
+    prefs.setValue(key, value)
+    prefs.save()
+  }
+
+  @AfterClass
+  def deleteTestProject {
+    project.underlying.delete(true, null)
+  }
+
 }
 
 class ContinuationPluginSettingsTest {
   import ContinuationPluginSettingsTest._
 
   @Test
   def continuationsPluginIsAlwaysLoaded() {
-    project.storage.setToDefault("Xpluginsdir")
-    project.storage.setToDefault("Xplugin")
+    setPrefToDefault("Xpluginsdir")
+    setPrefToDefault("Xplugin")
+    forceEnableContinuationForNewerScalaVersion()
+    project.resetPresentationCompiler()
     val plugins = loadedPlugins(project)
     Assert.assertEquals("Loaded plugins: ", List("continuations"), loadedPlugins(project))
   }
 
   @Test
   def loadContinuationsPluginVia_XpluginsdirCompilerSetting() {
-    project.storage.setValue("Xpluginsdir", ScalaPlugin.plugin.defaultPluginsDir)
-    project.storage.setValue("Xplugin", "/doesnotexits")
+    setPrefValue("Xpluginsdir", ScalaPlugin.plugin.defaultPluginsDir)
+    setPrefValue("Xplugin", "/doesnotexits")
+    forceEnableContinuationForNewerScalaVersion()
     project.resetPresentationCompiler()
     val plugins = loadedPlugins(project)
     Assert.assertEquals("Loaded plugins: ", List("continuations"), loadedPlugins(project))
   }
 
   @Test
   def loadContinuationsPluginVia_XpluginCompilerSetting() {
-    project.storage.setValue("Xpluginsdir", "/doesnotexist")
-    project.storage.setValue("Xplugin", ScalaPlugin.plugin.defaultPluginsDir + File.separator + "continuations.jar")
+    setPrefValue("Xpluginsdir", "/doesnotexist")
+    setPrefValue("Xplugin", ScalaPlugin.plugin.defaultPluginsDir + File.separator + "continuations.jar")
+    forceEnableContinuationForNewerScalaVersion()
     project.resetPresentationCompiler()
     val plugins = loadedPlugins(project)
     Assert.assertEquals("Loaded plugins: ", List("continuations"), loadedPlugins(project))
   }
 
   @Test
   def continuationPluginCannotBeLoadedWhen_pluginsDir_pointsToDirectoryThatDoesNotContainContinuationsPluginJar() {
-    project.storage.setValue("Xpluginsdir", "/doesnotexist")
-    project.storage.setValue("Xplugin", "/doesnotexits")
+    setPrefValue("Xpluginsdir", "/doesnotexist")
+    setPrefValue("Xplugin", "/doesnotexits")
+    forceEnableContinuationForNewerScalaVersion()
     project.resetPresentationCompiler()
 
     project.underlying.build(IncrementalProjectBuilder.CLEAN_BUILD, new NullProgressMonitor)
@@ -60,4 +97,10 @@ class ContinuationPluginSettingsTest {
     val plugins = project.withPresentationCompiler(comp => comp.plugins)(List[Plugin]())
     plugins.map(_.name)
   }
+
+  private def forceEnableContinuationForNewerScalaVersion() {
+    if (TestUtil.installedScalaVersionGreaterOrEqualsTo(new Version(2, 11, 0)))
+      setPrefValue("P", "continuations:enable")
+  }
+
 }

org.scala-ide.sdt.core/src/scala/tools/eclipse/ScalaProject.scala

@@ -6,7 +6,6 @@
 package scala.tools.eclipse
 
 import java.io.File.pathSeparator
-
 import scala.collection.immutable
 import scala.collection.mutable
 import scala.reflect.internal.util.BatchSourceFile
@@ -24,7 +23,6 @@ import scala.tools.eclipse.util.Trim
 import scala.tools.eclipse.util.Utils
 import scala.tools.nsc.MissingRequirementError
 import scala.tools.nsc.Settings
-
 import org.eclipse.core.resources.IContainer
 import org.eclipse.core.resources.IFile
 import org.eclipse.core.resources.IMarker
@@ -47,6 +45,7 @@ import org.eclipse.ui.IEditorPart
 import org.eclipse.ui.IPartListener
 import org.eclipse.ui.IWorkbenchPart
 import org.eclipse.ui.part.FileEditorInput
+import org.eclipse.jface.preference.IPersistentPreferenceStore
 
 trait BuildSuccessListener {
   def buildSuccessful(): Unit
@@ -554,7 +553,7 @@ class ScalaProject private (val underlying: IProject) extends ClasspathManagemen
    *  @see  #1001241.
    *  @see `storage` for a method that decides based on user preference
    */
-  def projectSpecificStorage: IPreferenceStore = {
+  def projectSpecificStorage: IPersistentPreferenceStore = {
     new PropertyStore(underlying, ScalaPlugin.prefStore, plugin.pluginId)
   }