Shut down actors.

modules/kobalt-plugin-api/src/main/kotlin/com/beust/kobalt/api/IPluginActor.kt

@@ -1,6 +1,11 @@
 package com.beust.kobalt.api
 
-interface IPluginActor
+interface IPluginActor {
+    /**
+     * Clean up any state that your actor might have saved so it can be run again.
+     */
+    fun shutdownActors() {}
+}
 
 interface IContributor : IPluginActor
 

modules/kobalt-plugin-api/src/main/kotlin/com/beust/kobalt/internal/JvmCompilerPlugin.kt

@@ -226,8 +226,13 @@ open class JvmCompilerPlugin @Inject constructor(
 
     val allProjects = arrayListOf<ProjectDescription>()
 
+    // IProjectContributor
     override fun projects() = allProjects
 
+    override fun shutdownActors() {
+        allProjects.clear()
+    }
+
     fun addDependentProjects(project: Project, dependents: List<Project>) {
         project.projectExtra.dependsOn.addAll(dependents)
         with(ProjectDescription(project, dependents)) {

modules/kobalt-plugin-api/src/main/kotlin/com/beust/kobalt/internal/KobaltPluginXml.kt

@@ -168,6 +168,22 @@ class PluginInfo(val xml: KobaltPluginXml, val classLoader: ClassLoader?) {
         }
     }
 
+    fun shutdown() {
+        listOf(projectContributors, classpathContributors, initContributors,
+                repoContributors, compilerFlagContributors, compilerInterceptors,
+                sourceDirectoriesInterceptors, buildDirectoryInterceptors,
+                runnerContributors, testRunnerContributors, classpathInterceptors,
+                compilerContributors, docContributors, sourceDirContributors,
+                testSourceDirContributors, buildConfigFieldContributors,
+                taskContributors, assemblyContributors,
+                incrementalAssemblyContributors
+            ).forEach {
+                it.forEach {
+                    it.shutdownActors()
+                }
+            }
+    }
+
     /**
      * Populate pluginInfo with what was found in the plug-in's kobalt-plugin.xml
      */