InvalidMutabilityException when TestScope is frozen

[rickclephas]

I am trying to update my coroutines tests to use runTest instead of runBlocking.
The code under test causes the TestScope to be frozen (which is expected) resulting in the following InvalidMutabilityException:

kotlin.native.concurrent.InvalidMutabilityException: mutation attempt of frozen kotlinx.coroutines.internal.ThreadSafeHeap@52a0d8
	at kotlin.Throwable#<init>(/opt/buildAgent/work/6326934d18cfe24e/kotlin/kotlin-native/runtime/src/main/kotlin/kotlin/Throwable.kt:24)
	at kotlin.Exception#<init>(/opt/buildAgent/work/6326934d18cfe24e/kotlin/kotlin-native/runtime/src/main/kotlin/kotlin/Exceptions.kt:23)
	at kotlin.RuntimeException#<init>(/opt/buildAgent/work/6326934d18cfe24e/kotlin/kotlin-native/runtime/src/main/kotlin/kotlin/Exceptions.kt:34)
	at kotlin.native.concurrent.InvalidMutabilityException#<init>(/opt/buildAgent/work/6326934d18cfe24e/kotlin/kotlin-native/runtime/src/main/kotlin/kotlin/native/concurrent/Freezing.kt:24)
	at <global>.ThrowInvalidMutabilityException(/opt/buildAgent/work/6326934d18cfe24e/kotlin/kotlin-native/runtime/src/main/kotlin/kotlin/native/concurrent/Internal.kt:109)
	at <global>.MutationCheck(Unknown Source)
	at kotlinx.coroutines.internal.ThreadSafeHeap.<set-a>#internal(/opt/buildAgent/work/44ec6e850d5c63f0/kotlinx-coroutines-core/common/src/internal/ThreadSafeHeap.kt:26)
	at kotlinx.coroutines.internal.ThreadSafeHeap.realloc#internal(/opt/buildAgent/work/44ec6e850d5c63f0/kotlinx-coroutines-core/common/src/internal/ThreadSafeHeap.kt:145)
	at kotlinx.coroutines.internal.ThreadSafeHeap#addImpl(/opt/buildAgent/work/44ec6e850d5c63f0/kotlinx-coroutines-core/native/src/Debug.kt:17)
	at kotlinx.coroutines.internal.ThreadSafeHeap#addLast(/opt/buildAgent/work/88b0986a7186d029/atomicfu/src/nativeMain/kotlin/kotlinx/atomicfu/locks/Synchronized.kt:38)
	at kotlinx.coroutines.test.TestCoroutineScheduler#registerEvent(/opt/buildAgent/work/44ec6e850d5c63f0/kotlinx-coroutines-test/common/src/TestCoroutineScheduler.kt:72)
	at kotlinx.coroutines.test.StandardTestDispatcherImpl.dispatch#internal(/opt/buildAgent/work/44ec6e850d5c63f0/kotlinx-coroutines-test/common/src/TestCoroutineDispatchers.kt:155)
	at kotlinx.coroutines.internal#resumeCancellableWith__at__kotlin.coroutines.Continuation<0:0>(/opt/buildAgent/work/44ec6e850d5c63f0/kotlinx-coroutines-core/common/src/internal/DispatchedContinuation.kt:282)
	at kotlinx.coroutines.intrinsics#startCoroutineCancellable__at__kotlin.coroutines.SuspendFunction1<0:0,0:1>(/opt/buildAgent/work/44ec6e850d5c63f0/kotlinx-coroutines-core/common/src/intrinsics/Cancellable.kt:30)
	at kotlinx.coroutines#startCoroutineImpl(/opt/buildAgent/work/44ec6e850d5c63f0/kotlinx-coroutines-core/common/src/Builders.common.kt:192)
	at kotlinx.coroutines.startCoroutine#internal(/opt/buildAgent/work/44ec6e850d5c63f0/kotlinx-coroutines-core/native/src/Builders.kt:147)
	at kotlinx.coroutines#startAbstractCoroutine(/opt/buildAgent/work/44ec6e850d5c63f0/kotlinx-coroutines-core/native/src/Builders.kt:118)
	at kotlinx.coroutines.AbstractCoroutine#start(/opt/buildAgent/work/44ec6e850d5c63f0/kotlinx-coroutines-core/common/src/AbstractCoroutine.kt:130)
	at kotlinx.coroutines#launch__at__kotlinx.coroutines.CoroutineScope(/opt/buildAgent/work/44ec6e850d5c63f0/kotlinx-coroutines-core/common/src/Builders.common.kt:56)
	at kotlinx.coroutines#launch$default__at__kotlinx.coroutines.CoroutineScope(/opt/buildAgent/work/44ec6e850d5c63f0/kotlinx-coroutines-core/common/src/Builders.common.kt:47)

The old code looks like this:

@Test
fun `ensure completion callback is invoked`() = runBlocking {
    val flow = flow<RandomValue> {  }
    val job = Job()
    val nativeFlow = flow.asNativeFlow(CoroutineScope(job))
    val completionCount = AtomicInt(0)
    nativeFlow({ _, _ -> }, { error, _ ->
        assertNull(error, "Flow should complete without an error")
        completionCount.increment()
    })
    job.children.forEach { it.join() } // Waits for the collection to complete
    assertEquals(1, completionCount.value, "Completion callback should be called once")
}

converting it to use runTest like this results in the InvalidMutabilityException:

@Test
fun `ensure completion callback is invoked`() = runTest {
    val flow = flow<RandomValue> {  }
    val nativeFlow = flow.asNativeFlow(this)
    val completionCount = AtomicInt(0)
    nativeFlow({ _, _ -> }, { error, _ ->
        assertNull(error, "Flow should complete without an error")
        completionCount.increment()
    })
    runCurrent()
    assertEquals(1, completionCount.value, "Completion callback should be called once")
}

[ankushg]

If it helps to have code to check out and run, you can check out this PR: https://github.com/rickclephas/KMP-NativeCoroutines/pull/43/files

• NativeFlow.kt is what we end up freezing so it can be freely moved across threads. When migrating to runTest, we this freezes TestCoroutineScope and causes this issue
• AppleNativeFlowTests.kt use the runBlocking approach and are passing.
• NativeFlowTests.kt use the runTest approach and are failing on Native platforms due to the freezing issue.

[qwwdfsad]

Please see #462 (comment)

We do no longer support new coroutines features with old memory model, only with a new one