Prevent StackOverflowError in CompletableFuture.asDeferred and proper… (

Kotlin#2731)

Prevent StackOverflowError in CompletableFuture.asDeferred and properly report exceptions from completion handlers

* It turned out that 'cancel' on completed future tries to help and invoke 'whenComplete' handlers that also invoke 'cancel' on the very same future
* Use top-level exception handler as a last resort to deliver an exception

Fixes Kotlin#2730

integration/kotlinx-coroutines-guava/src/ListenableFuture.kt

@@ -136,11 +136,13 @@ public fun <T> ListenableFuture<T>.asDeferred(): Deferred<T> {
         override fun onSuccess(result: T?) {
             // Here we work with flexible types, so we unchecked cast to trick the type system
             @Suppress("UNCHECKED_CAST")
-            deferred.complete(result as T)
+            runCatching { deferred.complete(result as T) }
+                .onFailure { handleCoroutineException(EmptyCoroutineContext, it) }
         }
 
         override fun onFailure(t: Throwable) {
-            deferred.completeExceptionally(t)
+            runCatching { deferred.completeExceptionally(t) }
+                .onFailure { handleCoroutineException(EmptyCoroutineContext, it) }
         }
     }, MoreExecutors.directExecutor())
 

integration/kotlinx-coroutines-guava/test/FutureAsDeferredUnhandledCompletionExceptionTest.kt

@@ -0,0 +1,46 @@
+/*
+ * Copyright 2016-2021 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
+ */
+
+package kotlinx.coroutines.guava
+
+import com.google.common.util.concurrent.*
+import kotlinx.coroutines.*
+import org.junit.*
+import org.junit.Test
+import kotlin.test.*
+
+class FutureAsDeferredUnhandledCompletionExceptionTest : TestBase() {
+
+    // This is a separate test in order to avoid interference with uncaught exception handlers in other tests
+    private val exceptionHandler = Thread.getDefaultUncaughtExceptionHandler()
+    private lateinit var caughtException: Throwable
+
+    @Before
+    fun setUp() {
+        Thread.setDefaultUncaughtExceptionHandler { _, e -> caughtException = e }
+    }
+
+    @After
+    fun tearDown() {
+        Thread.setDefaultUncaughtExceptionHandler(exceptionHandler)
+    }
+
+    @Test
+    fun testLostExceptionOnSuccess() = runTest {
+        val future = SettableFuture.create<Int>()
+        val deferred = future.asDeferred()
+        deferred.invokeOnCompletion { throw TestException() }
+        future.set(1)
+        assertTrue { caughtException is CompletionHandlerException && caughtException.cause is TestException }
+    }
+
+    @Test
+    fun testLostExceptionOnFailure() = runTest {
+        val future = SettableFuture.create<Int>()
+        val deferred = future.asDeferred()
+        deferred.invokeOnCompletion { throw TestException() }
+        future.setException(TestException2())
+        assertTrue { caughtException is CompletionHandlerException && caughtException.cause is TestException }
+    }
+}

integration/kotlinx-coroutines-guava/test/ListenableFutureTest.kt

@@ -11,6 +11,7 @@ import org.junit.Ignore
 import org.junit.Test
 import java.util.concurrent.*
 import java.util.concurrent.CancellationException
+import java.util.concurrent.atomic.*
 import kotlin.test.*
 
 class ListenableFutureTest : TestBase() {
@@ -755,4 +756,23 @@ class ListenableFutureTest : TestBase() {
         future(start = CoroutineStart.ATOMIC) { }
         future(start = CoroutineStart.UNDISPATCHED) { }
     }
+
+    @Test
+    fun testStackOverflow() = runTest {
+        val future = SettableFuture.create<Int>()
+        val completed = AtomicLong()
+        val count = 10000L
+        val children = ArrayList<Job>()
+        for (i in 0 until count) {
+            children += launch(Dispatchers.Default) {
+                future.asDeferred().await()
+                completed.incrementAndGet()
+            }
+        }
+        future.set(1)
+        withTimeout(60_000) {
+            children.forEach { it.join() }
+            assertEquals(count, completed.get())
+        }
+    }
 }

integration/kotlinx-coroutines-jdk8/src/future/Future.kt

@@ -126,13 +126,18 @@ public fun <T> CompletionStage<T>.asDeferred(): Deferred<T> {
     }
     val result = CompletableDeferred<T>()
     whenComplete { value, exception ->
-        if (exception == null) {
-            // the future has completed normally
-            result.complete(value)
-        } else {
-            // the future has completed with an exception, unwrap it consistently with fast path
-            // Note: In the fast-path the implementation of CompletableFuture.get() does unwrapping
-            result.completeExceptionally((exception as? CompletionException)?.cause ?: exception)
+        try {
+            if (exception == null) {
+                // the future has completed normally
+                result.complete(value)
+            } else {
+                // the future has completed with an exception, unwrap it consistently with fast path
+                // Note: In the fast-path the implementation of CompletableFuture.get() does unwrapping
+                result.completeExceptionally((exception as? CompletionException)?.cause ?: exception)
+            }
+        } catch (e: Throwable) {
+            // We come here iff the internals of Deferred threw an exception during its completion
+            handleCoroutineException(EmptyCoroutineContext, e)
         }
     }
     result.cancelFutureOnCompletion(future)

integration/kotlinx-coroutines-jdk8/test/future/FutureAsDeferredUnhandledCompletionExceptionTest.kt

@@ -0,0 +1,38 @@
+/*
+ * Copyright 2016-2021 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
+ */
+
+package future
+
+import kotlinx.coroutines.*
+import kotlinx.coroutines.future.*
+import org.junit.*
+import org.junit.Test
+import java.util.concurrent.*
+import kotlin.test.*
+
+class FutureAsDeferredUnhandledCompletionExceptionTest : TestBase() {
+
+    // This is a separate test in order to avoid interference with uncaught exception handlers in other tests
+    private val exceptionHandler = Thread.getDefaultUncaughtExceptionHandler()
+    private lateinit var caughtException: Throwable
+
+    @Before
+    fun setUp() {
+        Thread.setDefaultUncaughtExceptionHandler { _, e -> caughtException = e }
+    }
+
+    @After
+    fun tearDown() {
+        Thread.setDefaultUncaughtExceptionHandler(exceptionHandler)
+    }
+
+    @Test
+    fun testLostException() = runTest {
+        val future = CompletableFuture<Int>()
+        val deferred = future.asDeferred()
+        deferred.invokeOnCompletion { throw TestException() }
+        future.complete(1)
+        assertTrue { caughtException is CompletionHandlerException && caughtException.cause is TestException }
+    }
+}

integration/kotlinx-coroutines-jdk8/test/future/FutureTest.kt

@@ -575,4 +575,23 @@ class FutureTest : TestBase() {
         future(start = CoroutineStart.ATOMIC) { }
         future(start = CoroutineStart.UNDISPATCHED) { }
     }
+
+    @Test
+    fun testStackOverflow() = runTest {
+        val future = CompletableFuture<Int>()
+        val completed = AtomicLong()
+        val count = 10000L
+        val children = ArrayList<Job>()
+        for (i in 0 until count) {
+            children += launch(Dispatchers.Default) {
+                future.asDeferred().await()
+                completed.incrementAndGet()
+            }
+        }
+        future.complete(1)
+        withTimeout(60_000) {
+            children.forEach { it.join() }
+            assertEquals(count, completed.get())
+        }
+    }
 }

kotlinx-coroutines-core/jvm/src/Future.kt

@@ -13,20 +13,20 @@ import java.util.concurrent.*
  * Cancels a specified [future] when this job is cancelled.
  * This is a shortcut for the following code with slightly more efficient implementation (one fewer object created).
  * ```
- * invokeOnCompletion { future.cancel(false) }
+ * invokeOnCompletion { if (it != null) future.cancel(false) }
  * ```
  *
  * @suppress **This an internal API and should not be used from general code.**
  */
 @InternalCoroutinesApi
 public fun Job.cancelFutureOnCompletion(future: Future<*>): DisposableHandle =
-    invokeOnCompletion(handler = CancelFutureOnCompletion(future)) // TODO make it work only on cancellation as well?
+    invokeOnCompletion(handler = CancelFutureOnCompletion(future))
 
 /**
  * Cancels a specified [future] when this job is cancelled.
  * This is a shortcut for the following code with slightly more efficient implementation (one fewer object created).
  * ```
- * invokeOnCancellation { future.cancel(false) }
+ * invokeOnCancellation { if (it != null) future.cancel(false) }
  * ```
  */
 public fun CancellableContinuation<*>.cancelFutureOnCancellation(future: Future<*>): Unit =
@@ -38,15 +38,15 @@ private class CancelFutureOnCompletion(
     override fun invoke(cause: Throwable?) {
         // Don't interrupt when cancelling future on completion, because no one is going to reset this
         // interruption flag and it will cause spurious failures elsewhere
-        future.cancel(false)
+        if (cause != null) future.cancel(false)
     }
 }
 
 private class CancelFutureOnCancel(private val future: Future<*>) : CancelHandler()  {
     override fun invoke(cause: Throwable?) {
         // Don't interrupt when cancelling future on completion, because no one is going to reset this
         // interruption flag and it will cause spurious failures elsewhere
-        future.cancel(false)
+        if (cause != null)  future.cancel(false)
     }
     override fun toString() = "CancelFutureOnCancel[$future]"
 }