IllegalStateException thrown when change a MutableState value in the background: "Reading a state that was created after the snapshot was taken or in a snapshot that has not yet been applied" [166486000]

Fixed

Bug

Status Update

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Description

ma...@gmail.com

created issue #1

Aug 26, 2020 09:19PM

Version of Gradle Plugin: 4.2.0-alpha07
Version of Gradle: 6.6
Version of Java: 1.8
OS: Android 10

Compose options:

composeOptions {
    kotlinCompilerVersion "1.4.0"
    kotlinCompilerExtensionVersion "0.1.0-dev17"
}

Updating a MutableState value in the backgroung, sometimes I get the following error:

java.lang.IllegalStateException: Reading a state that was created after the snapshot was taken or in a snapshot that has not yet been applied
        at androidx.compose.runtime.snapshots.SnapshotKt.readError(Snapshot.kt:1495)
        at androidx.compose.runtime.snapshots.SnapshotKt.current(Snapshot.kt:1654)
        at androidx.compose.runtime.SnapshotMutableState.setValue(MutableState.kt:499)
        at com.manueldidonna.redhex.inventory.FakeInventory.fetchItems(Test.kt:26)
        at com.manueldidonna.redhex.inventory.TestKt$TestSnapshotCrash$2$1$1.invokeSuspend(Test.kt:60)

Code to reproduce is attached. See @Composable TestSnapshotCrash() It's a simple layout with 3 Tabs and a LazyColumn. Changing the tab, a new list is created in the background and assigned to a mutablestate. That state is used in the lazycolumn. If you change the tab very quickly and many times, the crash should happen.

TestSnapshotCrash.kt

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Comments

so...@google.com <so...@google.com> Aug 27, 2020 10:00AM

Assigned to ch...@google.com.

ch...@google.com <ch...@google.com> #2Aug 27, 2020 11:07PM

Project: platform/frameworks/support
Branch: androidx-main

commit 700259f0afe267dfe78b93db932a3cfd827a119d
Author: Sherry Hu <shuanghu@google.com>
Date: Mon May 10 14:23:09 2021

Add transition motion between fold and unfold.

Bug: 186211031
Test: manual
Change-Id: Id60f07311eca2d94ef91dc28ae45823a475160b4

M slidingpanelayout/slidingpanelayout/build.gradle
M slidingpanelayout/slidingpanelayout/src/androidTest/java/androidx/slidingpanelayout/widget/FoldTest.kt
M slidingpanelayout/slidingpanelayout/src/main/java/androidx/slidingpanelayout/widget/SlidingPaneLayout.java

https://android-review.googlesource.com/1702066

ch...@google.com <ch...@google.com> #3Aug 28, 2020 12:53AM

A workaround that will work now and into the future is using onCommit instead of launchInComposition():

    val scope = rememberCoroutineScope()
    onCommit(inventory) {
        scope.launch {
            val currentInventory = inventory.value
            withContext(Dispatchers.IO) {
                currentInventory.fetchItems()
            }
        }
    }

This has the unfortunate effect in dev17 and alpha1 of waiting a frame for launch to happen. This is fixed and will be released in alpha2. You can avoid this deferring by using onPreCommit now and then switch to using onCommit in alpha2 and beyond (which will deprecate onPreCommit and onCommit will switch to being the current behavior of onPreCommit). It is still unclear what should happen for the launchInComposition() case but we are thinking about it.

Again, the above work-around should not be necessary but will get you past this problem. I will leave this open until we have a solution.

ch...@google.com <ch...@google.com> Aug 28, 2020 05:58PM

Reassigned to ad...@google.com.

ap...@google.com <ap...@google.com> #4Aug 29, 2020 12:30AM

Marked as fixed.

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

commit 803f067eb6fbc77ca403f71fd65e32b96d3630d4
Author: Adam Powell <adamp@google.com>
Date: Fri Aug 28 12:32:58 2020

launchInComposition now launches dispatched

launchInComposition no longer launches as an undispatched coroutine. The
initial rationale for this behavior was to allow for subscriptions that
synchronously emit a first value or any other work that happens before
first suspension to have their results reflected more quickly, but this
produces inconsistent results for the frame, where composition and
layout/draw may see different values.

Remove the undispatched launch and let the coroutine launch proceed
normally.

Fixes: 166486000
Test: SuspendingEffectsTests.kt
Relnote: "launchInComposition no longer launches coroutines undispatched"
Change-Id: Ief6afbbd9cae98ef337808a5cb481f012df602c8

M compose/runtime/runtime/src/androidAndroidTest/kotlin/androidx/compose/runtime/SuspendingEffectsTests.kt
M compose/runtime/runtime/src/commonMain/kotlin/androidx/compose/runtime/Recomposer.kt

https://android-review.googlesource.com/1414949

Issue 166486000