Offline Support : Pages - handlePostUploadedWithoutError continuation issue

[jd-alexander]

Expected behavior

When a post is created and the Up button is pressed then it should just perform the auto-save without error.

Actual behavior

There are times when a crash occurs, seemingly because the continuation that represents the current upload was already resumed.

2020-02-07 11:45:13.904 E: FATAL EXCEPTION: DefaultDispatcher-worker-4
    Process: org.wordpress.android.beta, PID: 5736
    java.lang.IllegalStateException: Already resumed, but proposed with update kotlin.Unit
        at kotlinx.coroutines.CancellableContinuationImpl.alreadyResumedError(CancellableContinuationImpl.kt:332)
        at kotlinx.coroutines.CancellableContinuationImpl.resumeImpl(CancellableContinuationImpl.kt:327)
        at kotlinx.coroutines.CancellableContinuationImpl.resumeWith(CancellableContinuationImpl.kt:247)
        at org.wordpress.android.viewmodel.pages.PagesViewModel.handlePostUploadedWithoutError(PagesViewModel.kt:701)
        at org.wordpress.android.viewmodel.pages.PagesViewModel$start$1.invoke(PagesViewModel.kt:185)
        at org.wordpress.android.viewmodel.pages.PagesViewModel$start$1.invoke(PagesViewModel.kt:76)
        at org.wordpress.android.viewmodel.pages.PageListEventListener$onPostChanged$1.invokeSuspend(PageListEventListener.kt:100)
        at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33)
        at kotlinx.coroutines.DispatchedTask.run(DispatchedTask.kt:56)
        at kotlinx.coroutines.scheduling.CoroutineScheduler.runSafely(CoroutineScheduler.kt:561)
        at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.executeTask(CoroutineScheduler.kt:727)
        at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.runWorker(CoroutineScheduler.kt:667)
        at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.run(CoroutineScheduler.kt:655)

Steps to reproduce the behavior

1. I created a post.
2. added a title
3. Click on "Up" button in the editor.

Tested on WPAndroid #11191

[malinajirka]

@jd-alexander I believe this is happening because we call handlePostUploadedWithoutError twice in PageListEventListener. Once in onPostUploaded and once in OnPostChanged. When those two events happen at the same time, this continuation is accessed twice in a row. Do we really need to invoke handlePostUploadedWithoutError in OnPostChanged?

[jd-alexander]

Thanks, Jirka! I had discovered this bug during my work over the weekend but I didn't realize it was this one and changed it to the update event here

WordPress-Android/WordPress/src/main/java/org/wordpress/android/viewmodel/pages/PageListEventListener.kt

Line 100 in 65fbb75

handlePostUpdatedWithoutError.invoke()

So this can be closed.

[malinajirka]

@jd-alexander AFAIU your branch hasn't been merged yet, so I'm not sure we should be closing this issue. Wdyt?