Test background threads are stopped

libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/plugin/FinishBuildListener.kt

@@ -25,6 +25,8 @@ import java.util.concurrent.ScheduledExecutorService
 class FinishBuildListener(var pluginClassLoader: ParentLastURLClassLoader?) : BuildAdapter() {
     val log = Logging.getLogger(this.javaClass)
 
+    private var threadTracker: ThreadTracker? = ThreadTracker()
+
     override fun buildFinished(result: BuildResult?) {
         log.debug("Build finished listener")
 
@@ -38,6 +40,9 @@ class FinishBuildListener(var pluginClassLoader: ParentLastURLClassLoader?) : Bu
 
         pluginClassLoader = null
         result?.getGradle()?.removeListener(this)
+
+        threadTracker?.checkThreadLeak(result?.getGradle())
+        threadTracker = null
     }
 
     public fun removeThreadLocals() {

libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/plugin/ThreadTracker.kt

@@ -0,0 +1,42 @@
+package org.jetbrains.kotlin.gradle.plugin
+
+import org.gradle.api.Project
+import org.gradle.api.invocation.Gradle
+import org.gradle.api.logging.Logging
+import org.junit.Assert
+import java.util.HashSet
+
+public class ThreadTracker {
+    val log = Logging.getLogger(this.javaClass)
+    private var before: Collection<Thread>? = getThreads()
+
+    private fun getThreads(): Collection<Thread> = Thread.getAllStackTraces().keySet()
+
+    public fun checkThreadLeak(gradle: Gradle?) {
+        try {
+            val testThreads = gradle != null &&
+                    gradle.getRootProject().hasProperty("kotlin.gradle.test") &&
+                    !gradle.getRootProject().hasProperty("kotlin.gradle.noThreadTest")
+
+            Thread.sleep(if (testThreads) 200L else 50L)
+
+            val after = HashSet(getThreads())
+            after.removeAll(before!!)
+
+            for (thread in after) {
+                if (thread == Thread.currentThread()) continue
+
+                val name = thread.getName()
+
+                if (testThreads) {
+                    throw RuntimeException("Thread leaked: $thread: $name\n ${thread.getStackTrace().joinToString(separator = "\n", prefix = " at ")}")
+                }
+                else {
+                    log.info("Thread leaked: $thread: $name")
+                }
+            }
+        } finally {
+            before = null
+        }
+    }
+}

libraries/tools/kotlin-gradle-plugin/src/test/kotlin/org/jetbrains/kotlin/gradle/BaseGradleIT.kt

@@ -37,7 +37,7 @@ abstract class BaseGradleIT {
         copyDirRecursively(File(resourcesRootFile, "GradleWrapper-$wrapperVersion"), projectDir)
         val cmd = createCommand(tasks)
 
-        println("<=== Test build: ${this.projectName} $cmd ====>")
+        println("<=== Test build: ${this.projectName} $cmd ===>")
 
         val process = createProcess(cmd, projectDir)
 
@@ -96,7 +96,8 @@ abstract class BaseGradleIT {
 
     private fun Project.createCommand(params: Array<out String>): List<String> {
         val pathToKotlinPlugin = "-PpathToKotlinPlugin=" + File("local-repo").getAbsolutePath()
-        val tailParameters = params + listOf(pathToKotlinPlugin, "--no-daemon", "--${minLogLevel.name().toLowerCase()}")
+        val tailParameters = params +
+                listOf(pathToKotlinPlugin, "--no-daemon", "--${minLogLevel.name().toLowerCase()}", "-Pkotlin.gradle.test=true")
 
         return if (isWindows())
             listOf("cmd", "/C", "gradlew.bat") + tailParameters

libraries/tools/kotlin-gradle-plugin/src/test/kotlin/org/jetbrains/kotlin/gradle/Kotlin2JsGradlePluginIT.kt

@@ -8,7 +8,7 @@ class Kotlin2JsGradlePluginIT : BaseGradleIT() {
     Test fun testBuildAndClean() {
         val project = Project("kotlin2JsProject", "1.6")
 
-        project.build("build") {
+        project.build("build", "-Pkotlin.gradle.noThreadTest=true") {
             assertSuccessful()
             assertReportExists()