Having difficulties with suspendCancellableCorouti...

# coroutines

[Aslam Hossin]

Having difficulties with suspendCancellableCoroutine. Could someone please help me to figure out what I missed?

Caused by java.lang.IllegalStateException: Already resumed, but proposed with update kotlin.Unit
at kotlinx.coroutines.CancellableContinuationImpl.alreadyResumedError(CancellableContinuationImpl.kt:447)
at kotlinx.coroutines.CancellableContinuationImpl.resumeImpl(CancellableContinuationImpl.kt:412)
at kotlinx.coroutines.CancellableContinuationImpl.resumeImpl$default(CancellableContinuationImpl.kt:388)
at kotlinx.coroutines.CancellableContinuationImpl.resumeWith(CancellableContinuationImpl.kt:293)
at $wrapStatusListener$$inlined$suspendCancellableCoroutine$lambda$1.onSuccess(Misc.kt:88)
at java.lang.reflect.Method.invoke(Method.java)
at com.twilio.chat.internal.RethrowingForwarder$RethrowingProxy.invoke(RethrowingForwarder.java:121)
at java.lang.reflect.Proxy.invoke(Proxy.java:1006)
at $Proxy11.onSuccess()
at com.twilio.chat.internal.StatusListenerForwarder$1.run(StatusListenerForwarder.java:33)
at android.os.Handler.handleCallback(Handler.java:938)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:223)
at android.app.ActivityThread.main(ActivityThread.java:7660)
at java.lang.reflect.Method.invoke(Method.java)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947)

suspend fun <T> wrapStatusListener(value: T, block: (StatusListener) -> Unit): T {
    return suspendCancellableCoroutine { continuation: CancellableContinuation<T> ->
        block(object : StatusListener() {
            override fun onSuccess() {
                continuation.resume(value)
            }

            override fun onError(errorInfo: ErrorInfo) {
                continuation.resumeWithException(
                       Exception(
                        code = errorInfo.code,
                        status = errorInfo.status,
                        errorMessage = errorInfo.message
                    )
                )

            }
        })
    }
}

[uli]

Looks like onSuccess is called twice by block

[uli]

Or onSuccess being called after onError

[Aslam Hossin]

Yes but I don't know what is going here.

[uli]

I would say not coroutines related.

[Aslam Hossin]

Thank you so much for your help

[kevin.cianfarini]

it seems like StatusListener is a callback which gets invoked more than once. If that’s the case, you’re looking for a Flow, not suspend coroutine

[Aslam Hossin]

@kevin.cianfarini
Yes, Don't know how to avoid multiple invocation of Listener.

[Zach Klippenstein (he/him) [MOD]]

Depends on your use case.

If this method were named awaitStatus(), I would expect it to just wait for the next status update and return it. In that case you could use an AtomicBoolean to ensure that you only invoke resume once.

However, if you actually want to be able to return multiple status updates, then your function should return a Flow and probably use the callbackFlow builder, as previously suggested.

[uli]

What does block return? Is there a way to terminate?
I mean you are using suspendCancellableCoroutine and not handling cancelation. Maybe this is even the problem.
Try to either find a way how to ‘unregister’ your status listener on cancelation or use suspendCoroutine .
If your can unregister and your issue persists, you should also unregister in onSuccess and onError to avoid further calls to the listener.

[uli]

I guess you are wrapping things like this?
https://media.twiliocdn.com/sdk/android/chat/releases/0.11.2/docs/com/twilio/chat/ChatClient.html#registerGCMToken-java.l[…]lio.chat.StatusListener-

So there is no way to cancel an inflight request. Try using suspendCoroutine and please let us know if this solved your issue.

[Aslam Hossin]

@uli Definitely try it, a bit difficult to say it's solve my issue cause it's happening in production but can't reproduce 😕
Thank you all for your help and let you know if I figure out the details.