because i want to do nothing when Firebase callback is called twice

# coroutines

[Kulwinder Singh]

because i want to do nothing when Firebase callback is called twice

[louiscad]

Completion listener should be called only once. What API method is violating that?

[Kulwinder Singh]

from crashes i have found that Firestore's addOnSuccessListeneer is called twice on some devices

[Kulwinder Singh]

you can also check this issue https://github.com/Kotlin/kotlinx.coroutines/issues/48

[louiscad]

I asked which method. Firestore is an API, not a method

[Kulwinder Singh]

addOnSuccessListener is called twice on some devices

[louiscad]

That's not that generic method I'm asking for, I'm asking for the method returning the Task on which you use the await() extension function.

[Kulwinder Singh]

ooh sorry for misunderstanding,i'm using get() something like this colletion.whereEqualTo("level", level).get(source).await()

[louiscad]

Can you link that method?

[louiscad]

Also, could you show the error message when it's supposedly being called twice?

[Kulwinder Singh]

Fatal Exception: java.lang.IllegalStateException: Already resumed, but proposed with update kotlin.Unit
kotlinx.coroutines.CancellableContinuationImpl.alreadyResumedError (CancellableContinuationImpl.java:244)
kotlinx.coroutines.CancellableContinuationImpl.resumeImpl (CancellableContinuationImpl.java:239)
kotlinx.coroutines.CancellableContinuationImpl.resumeWith (CancellableContinuationImpl.java:168)
MyClass$loadSomethingSuspended$2$1.onLoaded (MyClassKt.java:94)

[louiscad]

It's probably that same issue I just opened following me checking the current code: https://github.com/Kotlin/kotlinx.coroutines/issues/1197

[louiscad]

I mentioned two possible workarounds, these sould fix your issue.

[Kulwinder Singh]

thanks @louiscad for your quick help 👍, i think now i only have to use try/catch

[Kulwinder Singh]

i have another solution as well, but don't know how good it is

suspend fun <T> Task<T>.await(): T {
    var continuation: CancellableContinuation<T>? = null
    addOnSuccessListener {
        continuation?.resume(it)
        continuation = null
    }.addOnFailureListener {
        continuation?.resumeWithException(it)
        continuation = null
    }
    return suspendCancellableCoroutine { continuation = it }
}

[Kulwinder Singh]

@louiscad is it safe to use above method?

[louiscad]

@Kulwinder Singh It'd still crash on post cancellation completation. You need to wrap the last line in a try finally and set the continuation variable back to null.