IllegalArgumentException during scroll in 3.0.0-alpha08 [172000108]

Fixed

Bug

Status Update

No update yet.

Description

an...@mevotemp.com

created issue #1

Oct 30, 2020 06:52AM

Component used: Paging 3 Version used: 3.0.0-alpha08 Devices/Android versions reproduced on: Samsung S9+ / Android 10

I have used codelab project: https://github.com/googlecodelabs/android-paging/tree/step13-19_network_and_database Branch: step13-19_network_and_database

Changes:

build.gradle:
    roomVersion = '2.3.0-alpha03'
    pagingVersion = '3.0.0-alpha08'

GithubRepository.kt:
    private const val NETWORK_PAGE_SIZE = 10

Got crash:

2020-10-30 08:42:26.339 E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.android.codelabs.paging, PID: 28502
    java.lang.IllegalArgumentException: Additional prepend event after prepend state is done
        at androidx.paging.SeparatorState.onInsert(Separators.kt:221)
        at androidx.paging.SeparatorState.onEvent(Separators.kt:173)
        at androidx.paging.SeparatorsKt$insertEventSeparators$$inlined$map$1$2.emit(Collect.kt:135)
        at androidx.paging.PagingDataKt$map$$inlined$transform$1$2.emit(Collect.kt:136)
        at kotlinx.coroutines.flow.FlowKt__ChannelsKt.emitAllImpl$FlowKt__ChannelsKt(Channels.kt:58)
        at kotlinx.coroutines.flow.FlowKt__ChannelsKt$emitAllImpl$1.invokeSuspend(Unknown Source:11)
        at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33)
        at kotlinx.coroutines.DispatchedTask.run(DispatchedTask.kt:56)
        at kotlinx.coroutines.EventLoop.processUnconfinedEvent(EventLoop.common.kt:69)
        at kotlinx.coroutines.DispatchedTaskKt.resumeUnconfined(DispatchedTask.kt:185)
        at kotlinx.coroutines.DispatchedTaskKt.dispatch(DispatchedTask.kt:108)
        at kotlinx.coroutines.CancellableContinuationImpl.dispatchResume(CancellableContinuationImpl.kt:308)
        at kotlinx.coroutines.CancellableContinuationImpl.completeResume(CancellableContinuationImpl.kt:395)
        at kotlinx.coroutines.channels.AbstractChannel$ReceiveElement.completeResumeReceive(AbstractChannel.kt:872)
        at kotlinx.coroutines.channels.ArrayChannel.offerInternal(ArrayChannel.kt:83)
        at kotlinx.coroutines.channels.AbstractSendChannel.send(AbstractChannel.kt:133)
        at androidx.paging.PageFetcherSnapshot.doLoad(PageFetcherSnapshot.kt:487)
        at androidx.paging.PageFetcherSnapshot$doLoad$1.invokeSuspend(Unknown Source:12)
        at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33)
        at kotlinx.coroutines.DispatchedTask.run(DispatchedTask.kt:56)
        at android.os.Handler.handleCallback(Handler.java:883)
        at android.os.Handler.dispatchMessage(Handler.java:100)
        at android.os.Looper.loop(Looper.java:237)
        at android.app.ActivityThread.main(ActivityThread.java:8125)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:496)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1100)

Steps to reproduce:

Build and rung the app
Scroll 3-5 pages down
Scroll up
Crash

It does not happen with 3.0.0-alpha07

Comments

cc...@google.com <cc...@google.com> #2Oct 30, 2020 03:35PM

Dustin, could this be a case of the extra, empty, state-only insert event being a surprise to the separators logic?

If the local last prepend event doesn't have remote state attached to it, I'd expect this crash to happen, because both events would report that they terminate start: https://cs.android.com/androidx/platform/frameworks/support/+/androidx-master-dev:paging/common/src/main/kotlin/androidx/paging/Separators.kt;l=194;drc=63c2310560810fd1ea3a7a90d15493d414ca090f

du...@google.com <du...@google.com> #3Oct 30, 2020 07:18PM

Hmm the check which throws this exception should wait for remote append done instead of source if remote is in use though - will need to dig into this a bit.

cc...@google.com <cc...@google.com> #4Oct 30, 2020 08:07PM

That's what the line in the link above should accomplish:

        val endState = prepend

As long as there's a mediator state, CombinedLoadStates.prepend will take the mediator copy

So the "instead of source" should be handled by treating that source=done prepend as non-terminal.

du...@google.com <du...@google.com> Oct 31, 2020 03:10AM

Accepted by du...@google.com.

ap...@google.com <ap...@google.com> #5Nov 2, 2020 10:28PM

Marked as fixed.

Project: platform/frameworks/support
Branch: androidx-master-dev

commit 45e2955b8ecc7881f0264bed9e982a9476cd6648
Author: Dustin Lam <dustinlam@google.com>
Date: Fri Oct 30 18:41:32 2020

Handle remote PREPEND / APPEND from previous generation

This fixes an issue with RemoteMediator state being multi-generational,
in cases where empty remote PREPEND / APPEND insert events are sent to
update LoadState from a previous generation, they can appear surface before
local PREPEND / APPEND has finished.

This change now checks for both source + remote state before adding the
footer / header to account for the broken assumption that remote APPEND
/ PREPEND always happens after source endOfPaginationReached.

Fixes: 172000108
Test: ./gradlew paging:paging-common:test
Change-Id: I3a260ff98f07f5be615192e31ce1dc533c8b75b8

M paging/common/src/main/kotlin/androidx/paging/Separators.kt
M paging/common/src/test/kotlin/androidx/paging/SeparatorsWithRemoteMediatorTest.kt

https://android-review.googlesource.com/1482701

ma...@gmail.com <ma...@gmail.com> #6Nov 10, 2020 10:16AM

Catched same error.
Separators with PagingSource works fine, but with RemoteMediator - IllegalArgEx appears.
When to expect a new release of paging 3?

Issue 172000108