Fastloader breaks loading MainDispatcherFactory on Jvm Desktop

[chrisjenx]

Describe the bug

FastLoader will fail in a way that loading the MainDispatcherFactory will appear missing despite being on the classpath.

Kotlin 1.9.20-rc
Compose 1.5.10-beta02
Java 20
Coroutines 1.7.3

Provide a Reproducer

With fast loader on:

fun main() {
   val factories = ServiceLoader.load(
        MainDispatcherFactory::class.java,
        MainDispatcherFactory::class.java.classLoader
    ).iterator().asSequence().toList()
    println(factories)
    val dispatcher = factories.maxByOrNull { it.loadPriority }?.tryCreateDispatcher(factories)
    println(dispatcher)
    println(Dispatchers.Main)
    runBlocking(Dispatchers.Main) {
    }
}

Log:

> Task :application:desktopApp:run
[kotlinx.coroutines.swing.SwingDispatcherFactory@f6c48ac]
Swing
Dispatchers.Main[missing]
Exception in thread "main" java.lang.IllegalStateException: Module with the Main dispatcher is missing. Add dependency providing the Main dispatcher, e.g. 'kotlinx-coroutines-android' and ensure it has the same version as 'kotlinx-coroutines-core'
	at kotlinx.coroutines.internal.MainDispatchersKt.throwMissingMainDispatcherException(MainDispatchers.kt:81)
	at kotlinx.coroutines.internal.MissingMainCoroutineDispatcher.missing(MainDispatchers.kt:112)
	at kotlinx.coroutines.internal.MissingMainCoroutineDispatcher.isDispatchNeeded(MainDispatchers.kt:96)
	at kotlinx.coroutines.internal.DispatchedContinuationKt.resumeCancellableWith(DispatchedContinuation.kt:319)
	at kotlinx.coroutines.intrinsics.CancellableKt.startCoroutineCancellable(Cancellable.kt:30)
	at kotlinx.coroutines.intrinsics.CancellableKt.startCoroutineCancellable$default(Cancellable.kt:25)
	at kotlinx.coroutines.CoroutineStart.invoke(CoroutineStart.kt:110)
	at kotlinx.coroutines.AbstractCoroutine.start(AbstractCoroutine.kt:126)
	at kotlinx.coroutines.BuildersKt__BuildersKt.runBlocking(Builders.kt:58)
	at kotlinx.coroutines.BuildersKt.runBlocking(Unknown Source)
	at co.....AppKt.main(App.kt:54)
	at co.....AppKt.main(App.kt)

You set System.setProperty("kotlinx.coroutines.fast.service.loader", "false")

> Task :application:desktopApp:run
[kotlinx.coroutines.swing.SwingDispatcherFactory@f6c48ac]
Dispatchers.Main
Dispatchers.Main

[chrisjenx]

This is a Multiplatfrom App by the way building a java application target, so I'm wondering if the classpath is slightly different? Happy try different things. But the work around is disabling fast loader for now which is fine

[dkhalanskyjb]

I could not reproduce this; for me, this code runs fine. Could you provide a complete project where this issue reproduces?

[chrisjenx]

Interesting, I'll try to create a sample project

[alexzhirkevich]

+1

System.setProperty("kotlinx.coroutines.fast.service.loader", "false")

This indeed helps. Thx

[chrisjenx]

@alexzhirkevich same issue for you? What is your project setup? I'm trying to create a micro project to reproduce

[alexzhirkevich]

@chrisjenx
Do you have Gitlive/Firebase dependency in your project? It causes this issue. It brings firebase to java using android dependencies and some workarounds. Probably this dependencies have META-INF service with android main dispatcher factory which replaces swing one.

Here is small repro. But this probably not the coroutines issue

[chrisjenx]

Yes I do. Interesting how that dep breaks it

…

On Sun, Nov 5, 2023 at 2:51 AM Alexander Zhirkevich < ***@***.***> wrote: @chrisjenx <https://github.com/chrisjenx> Do you have Gitlive/Firebase <https://github.com/gitLiveApp/firebase-kotlin-sdk/> dependency in your project? It causes this issue. It brings firebase to java <https://github.com/gitLiveApp/firebase-java-sdk> using android dependencies and some workarounds. Probably this dependencies have META-INF service with android main dispatcher factory which replaces swing one. Here is small repro <https://github.com/alexzhirkevich/repro-coroutines-issue>. But this probably not the coroutines issue — Reply to this email directly, view it on GitHub <#3914 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAI5DMMSP2KHNUCGXXYECB3YC5OTJAVCNFSM6AAAAAA56SSN6OVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMYTOOJTGY4DQNZXGU> . You are receiving this because you were mentioned.Message ID: ***@***.***>

[jflavio11]

I'm using Gitlive/Firebase dependency, too. The workaround that fixes this was disabling the service loader:

fun main() = application {
    
    System.setProperty("kotlinx.coroutines.fast.service.loader", "false")

    Window(onCloseRequest = ::exitApplication, title = "MyApp") {
         MyApp()
    }
}

[qwwdfsad]

@alexzhirkevich thank you for a self-contained reproducer!

[nbransby]

I'm using Gitlive/Firebase dependency, too. The workaround that fixes this was disabling the service loader:

fun main() = application {
    
    System.setProperty("kotlinx.coroutines.fast.service.loader", "false")

    Window(onCloseRequest = ::exitApplication, title = "MyApp") {
         MyApp()
    }
}

Interesting, as this ready happens inside the firebase-java-sdk:
https://github.com/GitLiveApp/firebase-java-sdk/blob/abf1a6a628b205215d804f3052818121ffdd3558/src/main/java/com/google/firebase/FirebasePlatform.kt#L14

[alexzhirkevich]

Interesting, as this ready happens inside the firebase-java-sdk:

Kotlin objects are lazy so this initialization probably performs way too late or doesn't perform at all

[nbransby]

Kotlin objects are lazy so this initialization probably performs way too late or doesn't perform at all

Will always perform before any coroune usage in the sdk

https://github.com/GitLiveApp/firebase-java-sdk/tree/abf1a6a628b205215d804f3052818121ffdd3558?tab=readme-ov-file#initializing-the-sdk

[jflavio11]

@nbransby nice catch. I think it is not working because how the dependency of the Firebase (GitLive) library is injected in the code. For instance, later I noticed that I was getting the problem at the very beginning of the code startup (the same time the Firebase dependency was injected through a Service Locator). As @alexzhirkevich mentioned, it's like a race condition problem on how or when that line is invoked 🤔

[nbransby]

Makes sense, glad there is a fix coming 👍