I get the following exception in my tests after upgrading decompose to 1.0.0: `Access from different...

# decompose

[benkuly]

I get the following exception in my tests after upgrading decompose to 1.0.0:
Access from different threads is detected, must be on the main thread only.Current thread: AWT-EventQueue-0 @coroutine#5082. First thread: AWT-EventQueue-0 @coroutine#11.
Thown here:

withContext(Dispatchers.Main.immediate) {
    push(configuration, onComplete) // <--
}

Any idea what's the problem?

[Arkadii Ivanov]

Most likely you created the root component on non-UI thread. Try following https://arkivanov.github.io/Decompose/component/overview/#jvmdesktop-with-compose

[Arkadii Ivanov]

If this is already what you are doing, or the problem is still there. Try adding the following at the very beginning of your application:

fun main() {
runOnUiThread {
val value = MutableValue(0)
value.value = 1
}

// The rest of the code
}
This will remember the correct thread, and all subsequent violations should throw proper stack traces.

[benkuly]

Hm okay. This does not work:

withContext(Dispatchers.Main.immediate)

Notice: It is common test-code. Therefore only a few view models are created...

[Arkadii Ivanov]

Ahh, this is in tests. I missed that.

[Arkadii Ivanov]

Could you post your test here?

[benkuly]

I can try creating a minimal reproducer.

[Arkadii Ivanov]

That would be very helpful

[Arkadii Ivanov]

The problem may be that you are using the real main dispatcher in tests. This may trigger the check. And this also makes your tests asynchronous.

You can pass all used dispatchers via constructor (with default values) and replace them in tests. E.g. with StandardTestDispatcher or UnconfinedDispatcher.

I will add an API to disable main thread checks in the next version, just in case one still wants to use real Dispatchers.

[Evegenii Khokhlov]

Also kotlinx-coroutines-test has very handy Dispatchers.setMain() method.

[Arkadii Ivanov]

Yes, this can be also used. Here are some docs (Android, but still can be useful) - https://developer.android.com/kotlin/coroutines/test#setting-main-dispatcher

[benkuly]

Setting Dispatchers.setMain() and don't using real main dispatchers was the trick. Thank you 🙂