Hello, I am having some issues with new `onUpload...

# ktor

[Anton Afanasev]

Hello,
I am having some issues with new onUpload API on KMM platform. Android works fine, but iOS produce an InvalidMutabilityException .I am looking for any feedback from the community. I am using ktor = 1.6.0

suspend fun uploadFile(
        url: String,
        byteArray: ByteArray,
        progressCallback: (Float) -> Unit
    ) {
        client.put<Unit>(url) {
            onUpload { bytesSendTotal: Long, contentLength: Long ->
                progressCallback((bytesSendTotal / contentLength.toFloat()) * 100)
            }
            body = byteArray
        }
    }

I call it from another class that is responsible for managing states of the uploaded object.

Dispatcher:

private val uploadDispatcher = CoroutineScope(Dispatchers.Main + SupervisorJob())

Call to the function:

uploadDispatcher.launch { api.uploadFile(url, byteArray) { progress ->
    data = data.copy(state = Uploading(progress))
        .also(onUploadProgress)
    }
}

where the onUploadProgress is lambda:

private val onUploadProgress: (Data) -> Unit,

As mentioned above, while executing this code on iOS I am receiving an InvalidMutabilityException
Looking into Ktor, it looks like the

UploadProgressListenerAttributeKey

marked with @SharedImmutable which makes it deeply frozen and freeze the objects it refers to.
Considering that when upload progress change I need to wrap and update state sof my internal objects - how should I do that using provided onUpload API?

[Igor Maric]

Same here, I tried using even newer version but it is the same.

[Aleksei Tirman [JB]]

@Anton Afanasev could you please share definitions for symbols in?

data = data.copy(state = Uploading(progress))
    .also(onUploadProgress)
}

[Anton Afanasev]

In my code data is actually a mutable map:

private val dataMap = mutableMapOf<String, Data>()

@Serializable
private class Data(
    val state: Data.State = Data.State.Idle,
    val id: String? = null,
    val fileName: String,
    var byteArray: ByteArray,
    var job: Job? = null,
) {

 @Serializable
    sealed class State {
        object Idle : State()
        object Deleted : State()
        object Detached : State()
        object Presigning : State()
        data class Uploading(val progress: Float) : State()
        data class Uploaded(val downloadUrl: String) : State()
        data class Sent(val downloadUrl: String) : State()
    }
}

I am using Data to report changes with this object. Potentially there are can be multiple data objects handle in the same time.

[Anton Afanasev]

progress is the outcome of progressCallback that is invoked every ktor.onUpdate() and simply convert the progress to percentage amount

[Aleksei Tirman [JB]]

Could you please simplify your code to make InvalidMutabilityException reproducible without using definitions for all those classes?

[Anton Afanasev]

Sure, let me do some small demo which reproduce the issue.

[Anton Afanasev]

Hi @Aleksei Tirman [JB] I made a small demo with downloadProgress. You can find it here. https://github.com/AfanasievAnton/Ktor-Download-POC.git

Also I was wondering about UploadProgressListenerAttributeKey and DownloadProgressListenerAttributeKey
in io.ktor.client.features
They annotated with @SharedImmutable. Wondering if it is necessary, as apparently this is the reason why my own listener and data structure that handle onUpload/onDownload become frozen as well. And since I am trying to mutate them I got an In InvalidMutabilityException.

Thank you in advance

[Aleksei Tirman [JB]]

@Anton Afanasev thank you for the sample project. Indeed, there is no way to mutate objects in a onDownload lambda if those objects were defined outside of it. I've created an issue KTOR-3068 to address this problem. Unfortunately, I don't know how to work around this issue.

[russhwolf]

That sample will work if you make flag atomic

[Anton Afanasev]

@Aleksei Tirman [JB] Thanks for your response. I would like to point that this limitation is relevant for both onDownload and onUpload listeners.

[Anton Afanasev]

@russhwolf It will work But as Ktor consumer I might have a bunch of dependencies involved in OnDownlod/OnUpload progress report. And I will have to convert all of them to atomic. Unless there are some tricks to avoid it.

[russhwolf]

Yeah, the native memory model takes some getting used to. Stately has some freeze-safe data structures which can help. https://github.com/touchlab/Stately