Extra recomposition when changing state and consuming shortly after, both in composition [393642162]

Assigned

Bug

Status Update

No update yet.

Description

ti...@google.com

created issue #1

Jan 31, 2025 11:02PM

There is an extra composition when running the following snippet.

More specifically, Expect: 1 recomposition after foo.prop changes. Actual: 2 recompositions


@Preview
@Composable
fun ReproExtraComposition() {
    var someOtherValue by remember { mutableStateOf(true) }
    var consumeFoo by remember { mutableStateOf(false) }
    val foo = remember { Foo() }
    LaunchedEffect(Unit) {
        delay(200)
        someOtherValue = !foo.prop
        consumeFoo = true
        println("LTD, foo property changed")
    }
    foo.prop = someOtherValue
    if (consumeFoo) {
        println("LTD, foo is consumed in composition")
        val prop1 = foo.prop
    }
}

@Stable
class Foo {
    var prop by mutableStateOf(true)
}

Comments

ti...@google.com <ti...@google.com> #2Jan 31, 2025 11:30PM

Also doesn't work in AS 2024.3.2 Canary 4 and Compose 1.8.0-beta01

an...@google.com <an...@google.com> #3Feb 1, 2025 12:06AM

Andrei: Is this the same as b/388030459?

al...@google.com <al...@google.com> #4Feb 6, 2025 05:44PM

Triage notes: Needs investigation. Assigning for later.

al...@google.com <al...@google.com> #5Feb 20, 2025 05:30PM

Reassigned to ch...@google.com.

Could you share the AppScaffoldTopBar function that fails here? This seems different from b/388030459 since it fails with expression that is not captured.

ch...@google.com <ch...@google.com> #6Feb 20, 2025 06:44PM

Status: Won't Fix (Intended Behavior)

Reconstructed from IR:

@Composable
fun AppScaffoldTopBar(
    showBackArrow: Boolean,
    showSearch: Boolean,
    title: String?,
    onBackClick: () -> Unit,
    modifier: Modifier = Modifier,
    actions: ImmutableList<AppScaffoldNavigationAction>
) {
    if (!showSearch) {
        TitledTopAppBar(
            title = title,
            showBackArrow = showBackArrow,
            modifier = modifier,
            actions = actions,
            onBackClick = onBackClick
        )
    } else {
        TopAppBar(
            title = {
                // Composable lambda for title
                AppScaffoldTopBarTitle(showBackArrow)
            },
            modifier = modifier,
            navigationIcon = {
                // Composable lambda for navigation icon
                AppScaffoldTopBarNavigationIcon(showBackArrow, onBackClick)
            },
            actions = {
                // Composable lambda for actions
                AppScaffoldTopBarActions(actions)
            }
        )
    }
}

This seems /extremely/ weird to me, because showSearch is just a regular parameter that is used in function body only once. We need more context about surrounding code to figure out why it crashed the compiler.

ti...@google.com <ti...@google.com> #7Feb 21, 2025 09:08PM

Status: Assigned (reopened)

sure i can paste more source. let me see what I can give you. do you need internals or externals?

Issue 393642162