Make TestDispatcher experimental, prohibit setMain(Dispatchers.Main), cleanup

Author: qwwdfsad

binary-compatibility-validator/reference-public-api/kotlinx-coroutines-test.txt

@@ -1,6 +1,5 @@
 public final class kotlinx/coroutines/test/TestDispatchers {
 	public static final fun resetMain (Lkotlinx/coroutines/Dispatchers;)V
 	public static final fun setMain (Lkotlinx/coroutines/Dispatchers;Lkotlinx/coroutines/CoroutineDispatcher;)V
-	public static synthetic fun setMain$default (Lkotlinx/coroutines/Dispatchers;Lkotlinx/coroutines/CoroutineDispatcher;ILjava/lang/Object;)V
 }
 

core/kotlinx-coroutines-core/src/internal/MainDispatchers.kt

@@ -37,8 +37,15 @@ public fun MainDispatcherFactory.tryCreateDispatcher(factories: List<MainDispatc
         MissingMainCoroutineDispatcher(cause, hintOnError())
     }
 
-private class MissingMainCoroutineDispatcher(private val cause: Throwable?, private val errorHint: String? = null) :
-    MainCoroutineDispatcher(), Delay {
+/** @suppress */
+@InternalCoroutinesApi
+public fun MainCoroutineDispatcher.isMissing(): Boolean = this is MissingMainCoroutineDispatcher
+
+private class MissingMainCoroutineDispatcher(
+    private val cause: Throwable?,
+    private val errorHint: String? = null
+) : MainCoroutineDispatcher(), Delay {
+
     override val immediate: MainCoroutineDispatcher get() = this
 
     override fun isDispatchNeeded(context: CoroutineContext): Boolean {

core/kotlinx-coroutines-test/src/TestDispatchers.kt

@@ -15,11 +15,12 @@ import kotlinx.coroutines.test.internal.*
  *
  * It is unsafe to call this method if alive coroutines launched in [Dispatchers.Main] exist.
  */
-public fun Dispatchers.setMain(dispatcher: CoroutineDispatcher = Dispatchers.Unconfined) {
+@ExperimentalCoroutinesApi
+public fun Dispatchers.setMain(dispatcher: CoroutineDispatcher) {
+    require(dispatcher !is TestMainDispatcher) { "Dispatchers.setMain(Dispatchers.Main) is prohibited, probably Dispatchers.resetMain() should be used instead" }
     val mainDispatcher = Dispatchers.Main
     require(mainDispatcher is TestMainDispatcher) { "TestMainDispatcher is not set as main dispatcher, have $mainDispatcher instead." }
     mainDispatcher.setDispatcher(dispatcher)
-
 }
 
 /**
@@ -29,6 +30,7 @@ public fun Dispatchers.setMain(dispatcher: CoroutineDispatcher = Dispatchers.Unc
  *
  * It is unsafe to call this method if alive coroutines launched in [Dispatchers.Main] exist.
  */
+@ExperimentalCoroutinesApi
 public fun Dispatchers.resetMain() {
     val mainDispatcher = Dispatchers.Main
     require(mainDispatcher is TestMainDispatcher) { "TestMainDispatcher is not set as main dispatcher, have $mainDispatcher instead." }

core/kotlinx-coroutines-test/src/internal/MainTestDispatcher.kt

@@ -17,14 +17,13 @@ internal class TestMainDispatcher(private val mainFactory: MainDispatcherFactory
     private val delegate: CoroutineDispatcher get() {
         if (_delegate != null) return _delegate!!
 
-        val newInstance = createDispatcher()
-        if (newInstance != null) {
-            _delegate = newInstance
-            return newInstance
+        mainFactory.tryCreateDispatcher(emptyList()).let {
+            // If we've failed to create a dispatcher, do no set _delegate
+            if (!isMissing()) {
+                _delegate = it
+            }
+            return it
         }
-
-        // Return missing dispatcher, but do not set _delegate
-        return mainFactory.tryCreateDispatcher(emptyList())
     }
 
     @Suppress("INVISIBLE_MEMBER")
@@ -60,14 +59,6 @@ internal class TestMainDispatcher(private val mainFactory: MainDispatcherFactory
     public fun resetDispatcher() {
         _delegate = null
     }
-
-    private fun createDispatcher(): CoroutineDispatcher? {
-        return try {
-            mainFactory.createDispatcher(emptyList())
-        } catch (cause: Throwable) {
-            null
-        }
-    }
 }
 
 internal class TestMainDispatcherFactory : MainDispatcherFactory {

core/kotlinx-coroutines-test/test/TestDispatchersTest.kt

@@ -6,6 +6,7 @@ package kotlinx.coroutines.test
 import kotlinx.coroutines.*
 import org.junit.*
 import org.junit.Test
+import java.lang.IllegalArgumentException
 import kotlin.coroutines.*
 import kotlin.test.*
 
@@ -16,6 +17,11 @@ class TestDispatchersTest : TestBase() {
         Dispatchers.resetMain()
     }
 
+    @Test(expected = IllegalArgumentException::class)
+    fun testSelfSet() = runTest {
+        Dispatchers.setMain(Dispatchers.Main)
+    }
+
     @Test
     fun testSingleThreadExecutor() = runTest {
         val mainThread = Thread.currentThread()

ui/kotlinx-coroutines-android/android-unit-tests/test/ordered/tests/FirstMockedMainTest.kt

@@ -15,7 +15,7 @@ open class FirstMockedMainTest : TestBase() {
 
     @Before
     fun setUp() {
-        Dispatchers.setMain()
+        Dispatchers.setMain(Dispatchers.Unconfined)
     }
 
     @After