[Pager] Page must be 0 when pageCount is 0

[zoltish]

Description
I received this crash log earlier today from someone rocking a Huawei Mate 20, running Android 10 (I dont think that matters?).

Fatal Exception: java.lang.IllegalArgumentException: page must be 0 when pageCount is 0
       at com.google.accompanist.pager.PagerState.requireCurrentPage(PagerState.kt:320)
       at com.google.accompanist.pager.PagerState.animateScrollToPage(PagerState.kt:195)
       at com.google.accompanist.pager.PagerState.animateScrollToPage$default(PagerState.java:191)
       at progression.design.structure.PagerKt$rememberPagerController$2.invokeSuspend(Pager.kt:108)
       at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33)
       at kotlinx.coroutines.DispatchedTask.run(DispatchedTask.kt:106)
       at androidx.compose.ui.platform.AndroidUiDispatcher.performTrampolineDispatch(AndroidUiDispatcher.android.kt:81)
       at androidx.compose.ui.platform.AndroidUiDispatcher.access$performTrampolineDispatch(AndroidUiDispatcher.android.kt:41)
       at androidx.compose.ui.platform.AndroidUiDispatcher$dispatchCallback$1.run(AndroidUiDispatcher.android.kt:2)
       at android.os.Handler.handleCallback(Handler.java:900)
       at android.os.Handler.dispatchMessage(Handler.java:103)
       at android.os.Looper.loop(Looper.java:219)
       at android.app.ActivityThread.main(ActivityThread.java:8393)
       at java.lang.reflect.Method.invoke(Method.java)
       at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:513)
       at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1055)

Steps to reproduce
This happened out in the wild, but the related code that actually triggered the crash looks like this. Basically used to synchronize an external states current selection with the pager page.

    LaunchedEffect(currentPage) {
        if (state.targetPage != currentPage) {
            state.animateScrollToPage(
                page = currentPage
            )
        }
    }

Additional context
I cant tell which screen of my app lead to this crash, but every screen thats using a pager has at least 1 page at all times.

compose = '1.2.0-alpha04'
accompanist = '0.24.3-alpha'

[andkulikov]

Didn't you file #859 already for exactly this?

Realistically LaunchedEffect is executed before the pager is laid out at least once so this block could be called before we know the needed info for performing the scroll. So you can't call it too early

[zoltish]

Oh snap. Sorry, I thought this was a new thing in the latest alpha release. I appreciate the explanation though, Ill work my way around it!

[kasem-sm]

@zoltish any work around you found? Thanks!

[undermark5]

This was fixed by #1195, which is included as of v0.24.11-rc