Hi guys. I'm going crazy with some code. I have 2 ...

# multiplatform

[coletz]

Hi guys. I'm going crazy with some code. I have 2 mpp, one I manually created like 2 months ago and one created with "new>project>kotlin mpp (ios/android)". The first one is working fine, while the second one is throwing an error on ios (kotlin.native.concurrent.InvalidMutabilityException: mutation attempt of frozen <object>@839b6268). The whole code is the same. Anyone ever had similar issue?

[coletz]

common code:

internal expect val ApplicationDispatcher: CoroutineDispatcher

class PokeApi {

    private val httpClient = HttpClient()

    fun getPokemonList(success: (PokemonList) -> Unit){
        GlobalScope.launch(ApplicationDispatcher){
            val json: String = httpClient.get {
                url("<https://pokeapi.co/api/v2/pokemon/>")
            }
            val deferred = GlobalScope.async(ApplicationDispatcher) {
                JSON.nonstrict.parse(PokemonList.serializer(), json)
            }
            success(deferred.await())
        }
    }
}

@Serializable
data class Pokemon(
    val name: String,
    val url: String
)

@Serializable
data class PokemonList(
    val count: Int,
    val results: List<Pokemon>
)

[thevery]

Try to freeze all the lambdas, e.g. http client callback

[thevery]

Recent KN releases are more strict on this, I've encountered similar issue

[pandawarrior]

Any solution for it yet? I believe it’s the same issue with mine on iOS

mutation attempt of frozen <object>@c4226468

private val client = HttpClient()

    fun callSimpleApi() {
        try {
            launch {
                getToolString()
            }
        } catch (e: Exception) {
            sampleView.returnString(e.toString())
        }
    }

    suspend fun getToolString() = client.get<String> {
        url("<https://tools.ietf.org/rfc/rfc1866.txt>")
    }

[Sabrina Namur]

I'm not sure, because you said both projects have the same code, but I got this problem with kotlin 1.3.11. With kotlin 1.3.10 everything works fine.

[pandawarrior]

Oh really? let me check with kotlin 1.3.10.

[pandawarrior]

@Sabrina Namur You are right, 1.3.11 is the problem. Thanks!

[coletz]

Oh, the code was the same but I had different kotlin version... Thanks! But I'd like to know how to freeze lambda... Can you provide an example @thevery?

[thevery]

Sure. Non-frozen:
listOf(1, 2, 3).filter { it: Int -> it % 2 == 0 }
Frozen:
listOf(1, 2, 3).filter({ it: Int -> it % 2 == 0 }.freeze())

[coletz]

Actually it's not possible to freeze on common code, right? One should call freeze on the iOS code, or I'm missing something?

[thevery]

I freeze on iOS side, in common you can create expect/actual or use https://github.com/touchlab/Stately

[coletz]

so stately is just defining empty expect for other platforms (eg android) in order to use freeze and other stuff on common code... Basically what I've just done, but I can't get how I should call .freeze() on the code I provided before. You said to freeze httpclient's lambda callback, but these are builders and not a lambda called on call completed. That's a coroutine so there's no callback. Sorry if this sound stupid 😅

[thevery]

ic. Can you try to log every line to get the actual crash reason?

[coletz]

yep!

[coletz]

class PokeApi {

    private val httpClient = HttpClient()

    fun getPokemonList(success: (PokemonList) -> Unit){
        1.log()
        GlobalScope.launch(ApplicationDispatcher){
            2.log()
            val json: String = httpClient.get {
                3.log()
                url("<https://pokeapi.co/api/v2/pokemon/>")
                4.log()
            }
            5.log()
            val deferred = GlobalScope.async(ApplicationDispatcher) {
                6.log()
                JSON.nonstrict.parse(PokemonList.serializer(), json)
            }
            7.log()
            success(deferred.await())
            8.log()
        }
    }
}

fun Int.log(){
    println("========= $this")
}

the crash is after log number 4

[thevery]

Looks like freeze is needed in ktor itself, @e5l do you know about this issue?

[e5l]

Yep, WIP. The fix would be available in the next minor release.

[Patrick Jackson]

Is this resolved now? Getting same exception with ktor 1.1.3 kotlin 1.3.21 coroutine 1.1.1

[e5l]

Nope, still [WIP] 😞. You could fix the exception by preventing client instance freeze(do not create it in global scope or object singleton)

[e5l]

Blocked by https://youtrack.jetbrains.com/issue/KT-30454

[coletz]

So it seems like KT-30454 is by design and nothing is "really" broken... That means we will need to always instantiate a new client every time. From your knowledge is it possible to instantiate the client inside something like a view model and use it multiple times or this will still crash?

[e5l]

Yes, and we testing the fix.