FakeFileSystem throws InvalidMutabilityException on Kotlin/Native

[kubode]

Hi, thanks for working on making Okio to Kotlin Multiplatform.

I have encountered InvalidMutabilityException when testing with FakeFileSystem on Kotlin/Native.
However, it’s working with FileSystem.SYSTEM as intended.

Environment

• Kotlin 1.4.32
• Kotlin Coroutines 1.4.3-native-mt
• com.squareup.okio:okio-multiplatform:3.0.0-alpha.6

Test code

    val path = "/path/to/file".toPath()

    @Test
    fun success() = runTest { // runTest: the same as runBlocking with Dispatchers.Main
        val fileSystem: FileSystem = FileSystem.SYSTEM
        val string = withContext(Dispatchers.Default) { fileSystem.read(path) { readUtf8() } }
        println(string)
    }

    @Test
    fun fail() = runTest {
        val fileSystem: FileSystem = FakeFileSystem()
        val string = withContext(Dispatchers.Default) { fileSystem.read(path) { readUtf8() } }
        println(string)
    }

Stack trace

kotlin.native.concurrent.InvalidMutabilityException: mutation attempt of frozen okio.fakefilesystem.FakeFileSystem.Element.File@d5c2b1e8
	at kotlin.Throwable#<init>(/Users/teamcity2/buildAgent/work/11ac87a349af04d5/runtime/src/main/kotlin/kotlin/Throwable.kt:23)
	at kotlin.Exception#<init>(/Users/teamcity2/buildAgent/work/11ac87a349af04d5/runtime/src/main/kotlin/kotlin/Exceptions.kt:23)
	at kotlin.RuntimeException#<init>(/Users/teamcity2/buildAgent/work/11ac87a349af04d5/runtime/src/main/kotlin/kotlin/Exceptions.kt:34)
	at kotlin.native.concurrent.InvalidMutabilityException#<init>(/Users/teamcity2/buildAgent/work/11ac87a349af04d5/runtime/src/main/kotlin/kotlin/native/concurrent/Freezing.kt:22)
	at <global>.ThrowInvalidMutabilityException(/Users/teamcity2/buildAgent/work/11ac87a349af04d5/runtime/src/main/kotlin/kotlin/native/concurrent/Internal.kt:93)
	at <global>.MutationCheck(Unknown Source)
	at okio.fakefilesystem.FakeFileSystem.Element.<set-lastAccessedAt>#internal(/Users/jwilson/Projects/okio/okio-fakefilesystem/src/commonMain/kotlin/okio/fakefilesystem/FakeFileSystem.kt:416)
	at okio.fakefilesystem.FakeFileSystem.Element.access#internal(/Users/jwilson/Projects/okio/okio-fakefilesystem/src/commonMain/kotlin/okio/fakefilesystem/FakeFileSystem.kt:442)
	at okio.fakefilesystem.FakeFileSystem.open#internal(/Users/jwilson/Projects/okio/okio-fakefilesystem/src/commonMain/kotlin/okio/fakefilesystem/FakeFileSystem.kt:315)
	at okio.fakefilesystem.FakeFileSystem#openReadOnly(/Users/jwilson/Projects/okio/okio-fakefilesystem/src/commonMain/kotlin/okio/fakefilesystem/FakeFileSystem.kt:260)
	at okio.fakefilesystem.FakeFileSystem#source(/Users/jwilson/Projects/okio/okio-fakefilesystem/src/commonMain/kotlin/okio/fakefilesystem/FakeFileSystem.kt:241)
	********
	at kotlin.coroutines.native.internal.BaseContinuationImpl#resumeWith(/Users/teamcity2/buildAgent/work/11ac87a349af04d5/runtime/src/main/kotlin/kotlin/coroutines/ContinuationImpl.kt:30)
	at kotlinx.coroutines.DispatchedTask#run(/opt/buildAgent/work/44ec6e850d5c63f0/kotlinx-coroutines-core/common/src/internal/DispatchedTask.kt:106)
	at kotlinx.coroutines.EventLoopImplBase#processNextEvent(/opt/buildAgent/work/44ec6e850d5c63f0/kotlinx-coroutines-core/common/src/EventLoop.common.kt:277)
	at kotlinx.coroutines#runEventLoop(/opt/buildAgent/work/44ec6e850d5c63f0/kotlinx-coroutines-core/native/src/Builders.kt:80)
	at kotlinx.coroutines.WorkerCoroutineDispatcherImpl.start$lambda-0#internal(/opt/buildAgent/work/44ec6e850d5c63f0/kotlinx-coroutines-core/native/src/Workers.kt:49)
	at kotlinx.coroutines.WorkerCoroutineDispatcherImpl.$start$lambda-0$FUNCTION_REFERENCE$35.invoke#internal(/opt/buildAgent/work/44ec6e850d5c63f0/kotlinx-coroutines-core/native/src/Workers.kt:47)
	at kotlinx.coroutines.WorkerCoroutineDispatcherImpl.$start$lambda-0$FUNCTION_REFERENCE$35.$<bridge-UNN>invoke(/opt/buildAgent/work/44ec6e850d5c63f0/kotlinx-coroutines-core/native/src/Workers.kt:47)
	at <global>.WorkerLaunchpad(/Users/teamcity2/buildAgent/work/11ac87a349af04d5/runtime/src/main/kotlin/kotlin/native/concurrent/Internal.kt:70)
	at <global>._ZN6Worker19processQueueElementEb(Unknown Source)
	at <global>._ZN12_GLOBAL__N_113workerRoutineEPv(Unknown Source)
	at <global>._pthread_start(Unknown Source)
	at <global>.thread_start(Unknown Source)

[swankjesse]

We might get this fixed for us for free with the new Kotlin/Native memory model. We need to adopt some locking in our FakeFileSystem for safe concurrent use.

[whataa]

The new Kotlin/Native memory model has been released in kotlin 1.7.20, so is there any progress here

[kubode]

True. I close this issue.