Introduce CoroutineDispatcher.asExecutor() extension

Fixes #1450
Kotlin · Aug 21, 2019 · 86c0367 · 86c0367
1 parent fbaedc4
commit 86c0367
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Showing 3 changed files with 38 additions and 5 deletions.
diff --git a/binary-compatibility-validator/reference-public-api/kotlinx-coroutines-core.txt b/binary-compatibility-validator/reference-public-api/kotlinx-coroutines-core.txt
@@ -293,6 +293,7 @@ public abstract class kotlinx/coroutines/ExecutorCoroutineDispatcher : kotlinx/c
 }
 
 public final class kotlinx/coroutines/ExecutorsKt {
+	public static final fun asExecutor (Lkotlinx/coroutines/CoroutineDispatcher;)Ljava/util/concurrent/Executor;
 	public static final fun from (Ljava/util/concurrent/Executor;)Lkotlinx/coroutines/CoroutineDispatcher;
 	public static final fun from (Ljava/util/concurrent/ExecutorService;)Lkotlinx/coroutines/ExecutorCoroutineDispatcher;
 }

diff --git a/kotlinx-coroutines-core/jvm/src/Executors.kt b/kotlinx-coroutines-core/jvm/src/Executors.kt
@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2018 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
+ * Copyright 2016-2019 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
  */
 
 package kotlinx.coroutines
@@ -45,6 +45,19 @@ public fun ExecutorService.asCoroutineDispatcher(): ExecutorCoroutineDispatcher
 public fun Executor.asCoroutineDispatcher(): CoroutineDispatcher =
     ExecutorCoroutineDispatcherImpl(this)
 
+/**
+ * Converts an instance of [CoroutineDispatcher] to an implementation of [Executor].
+ *
+ * It returns an original executor when used on the result of [Executor.asCoroutineDispatcher] extensions.
+ */
+public fun CoroutineDispatcher.asExecutor(): Executor =
+    (this as? ExecutorCoroutineDispatcher)?.executor ?: DispatcherExecutor(this)
+
+private class DispatcherExecutor(private val dispatcher: CoroutineDispatcher) : Executor {
+    override fun execute(block: Runnable) = dispatcher.dispatch(EmptyCoroutineContext, block)
+    override fun toString(): String = dispatcher.toString()
+}
+
 private class ExecutorCoroutineDispatcherImpl(override val executor: Executor) : ExecutorCoroutineDispatcherBase() {
     init {
         initFutureCancellation()

diff --git a/kotlinx-coroutines-core/jvm/test/ExecutorsTest.kt b/kotlinx-coroutines-core/jvm/test/ExecutorsTest.kt
@@ -1,11 +1,12 @@
 /*
- * Copyright 2016-2018 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
+ * Copyright 2016-2019 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
  */
 
 package kotlinx.coroutines
 
-import org.junit.Test
-import java.util.concurrent.Executors
+import org.junit.*
+import org.junit.Assert.*
+import java.util.concurrent.*
 
 class ExecutorsTest : TestBase() {
     private fun checkThreadName(prefix: String) {
@@ -32,14 +33,32 @@ class ExecutorsTest : TestBase() {
     }
 
     @Test
-    fun testToExecutor() {
+    fun testExecutorToDispatcher() {
         val executor = Executors.newSingleThreadExecutor { r -> Thread(r, "TestExecutor") }
         runBlocking(executor.asCoroutineDispatcher()) {
             checkThreadName("TestExecutor")
         }
         executor.shutdown()
     }
 
+    @Test
+    fun testConvertedDispatcherToExecutor() {
+        val executor: ExecutorService = Executors.newSingleThreadExecutor { r -> Thread(r, "TestExecutor") }
+        val dispatcher: CoroutineDispatcher = executor.asCoroutineDispatcher()
+        assertSame(executor, dispatcher.asExecutor())
+        executor.shutdown()
+    }
+
+    @Test
+    fun testDefaultDispatcherToExecutor() {
+        val latch = CountDownLatch(2)
+        Dispatchers.Default.asExecutor().execute {
+            checkThreadName("DefaultDispatcher")
+            latch.countDown()
+        }
+        latch.countDown()
+    }
+
     @Test
     fun testTwoThreads() {
         val ctx1 = newSingleThreadContext("Ctx1")