Rollback #2972, but leave a compatibility option with 1.6.0 (#3131)

The approach from 1.6.0 has proven itself as unstable and multiple hard-to-understand bugs have been reported: * JavaFx timer doesn't really work outside the main thread * The frequent initialization pattern "runBlocking { doSomethingThatMayCallDelay() }" used on the main thread during startup now silently deadlocks * The latter issue was reported both by Android and internal JB Compose users * The provided workaround with system property completely switches off the desired behaviour that e.g. Compose may rely on, potentially introducing new sources of invalid behaviour The original benefits does not outweigh these pitfalls, so the decision is to revert this changes in the minor release Fixes #3113 Fixes #3106
Kotlin · Jan 17, 2022 · 9169d09 · 9169d09
1 parent ce02a3f
commit 9169d09
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diff --git a/kotlinx-coroutines-core/jvm/src/DefaultExecutor.kt b/kotlinx-coroutines-core/jvm/src/DefaultExecutor.kt
@@ -8,7 +8,7 @@ import kotlinx.coroutines.internal.*
 import java.util.concurrent.*
 import kotlin.coroutines.*
 
-private val defaultMainDelayOptIn = systemProp("kotlinx.coroutines.main.delay", true)
+private val defaultMainDelayOptIn = systemProp("kotlinx.coroutines.main.delay", false)
 
 internal actual val DefaultDelay: Delay = initializeDefaultDelay()
 

diff --git a/ui/kotlinx-coroutines-android/test/HandlerDispatcherTest.kt b/ui/kotlinx-coroutines-android/test/HandlerDispatcherTest.kt
@@ -163,20 +163,19 @@ class HandlerDispatcherTest : TestBase() {
     }
 
     @Test
-    fun testDelayIsDelegatedToMain() = runTest {
+    fun testDelayIsNotDelegatedToMain() = runTest {
         val mainLooper = shadowOf(Looper.getMainLooper())
         mainLooper.pause()
         val mainMessageQueue = shadowOf(Looper.getMainLooper().queue)
         assertNull(mainMessageQueue.head)
         val job = launch(Dispatchers.Default, start = CoroutineStart.UNDISPATCHED) {
             expect(1)
-            delay(10_000_000)
-            expect(3)
+            delay(Long.MAX_VALUE)
+            expectUnreached()
         }
         expect(2)
-        assertNotNull(mainMessageQueue.head)
-        mainLooper.runOneTask()
-        job.join()
-        finish(4)
+        assertNull(mainMessageQueue.head)
+        job.cancelAndJoin()
+        finish(3)
     }
 }