Chat does not scroll to the bottom when submitting expenses while being at the top of the chat

[mitarachim]

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Version Number: 9.0.89-2
Reproducible in staging?: Yes
Reproducible in production?: No
If this was caught on HybridApp, is this reproducible on New Expensify Standalone?: N/A
If this was caught during regression testing, add the test name, ID and link from TestRail: https://expensify.testrail.io/index.php?/tests/view/5508042
Email or phone of affected tester (no customers): applausetester+100106kh@applause.expensifail.com
Issue reported by: Applause Internal Team
Device used: Mac 15.0 / Chrome
App Component: Chat Report View

Action Performed:

1. Go to staging.new.expensify.com
2. Open DM with any user.
3. Send about 50 messages so that the chat is scrollable.
4. Scroll to the top.
5. Submit an expense to the user.
6. Note that the chat scrolls to the bottom.
7. Scroll to the top again.
8. Submit another expense.

Expected Result:

Chat will scroll to the bottom every time user submits an expense while being at the top of the chat (production behavior).

Actual Result:

Chat only scrolls to the bottom when user submits the first expense. It no longer scrolls down when submitting more expenses while at the top of the chat.

Workaround:

Unknown

Platforms:

• Android: Standalone
• Android: HybridApp
• Android: mWeb Chrome
• iOS: Standalone
• iOS: HybridApp
• iOS: mWeb Safari
• MacOS: Chrome / Safari
• MacOS: Desktop

Screenshots/Videos

Bug6722304_1737676927307.20250124_075208.mp4

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[melvin-bot]

Triggered auto assignment to @rlinoz (DeployBlockerCash), see https://stackoverflowteams.com/c/expensify/questions/9980/ for more details.

[melvin-bot]

Triggered auto assignment to @sakluger (Bug), see https://stackoverflow.com/c/expensify/questions/14418 for more details. Please add this bug to a GH project, as outlined in the SO.

[melvin-bot]

💬 A slack conversation has been started in #expensify-open-source

[github-actions]

👋 Friendly reminder that deploy blockers are time-sensitive ⏱ issues! Check out the open `StagingDeployCash` deploy checklist to see the list of PRs included in this release, then work quickly to do one of the following:

1. Identify the pull request that introduced this issue and revert it.
2. Find someone who can quickly fix the issue.
3. Fix the issue yourself.

[samranahm]

🚨 Edited by proposal-police: This proposal was edited at 2025-01-24 15:20:14 UTC.

Proposal

Please re-state the problem that we are trying to solve in this issue.

Chat does not scroll to the bottom when submitting expenses while being at the top of the chat

What is the root cause of that problem?

when user create an expense this useEffect trigger

App/src/pages/home/report/ReportActionsList.tsx

Lines 487 to 499 in aa849f1

	useEffect(() => {
	if (!pendingBottomScroll || scrollingVerticalOffset.current === 0) {
	return;
	}
	if (isNewMessageDisplayed) {
	InteractionManager.runAfterInteractions(() => {
	setIsFloatingMessageCounterVisible(false);
	reportScrollManager.scrollToBottom();
	setPendingBottomScroll(false);
	});
	}
	}, [pendingBottomScroll, reportScrollManager, isNewMessageDisplayed]);

Here one of the dependency isNewMessageDisplayed check if the

lastAction?.reportActionID !== lastPrevVisibleAction?.reportActionID

that return true on first expense and useEffect condition

if (isNewMessageDisplayed) {

pass and it take us to bottom of the screen

but when we submit another expense both lastAction?.reportActionID and lastPrevVisibleAction?.reportActionID remain same that don't trigger the useEffect, and because isNewMessageDisplayed if false so it does't scroll to bottom.

What changes do you think we should make in order to solve the problem?

In isNewMessageDisplayed we should define a new const

 const isMultipleChildMoneyRequests = (lastAction?.childMoneyRequestCount ?? 0) > 1;

this will check if we have more than 1 childMoneyRequest and return true

const isNewMessageDisplayed = useMemo(() => {
        const prevActions = Object.values(prevSortedVisibleReportActionsObjects);
        const lastPrevVisibleAction = prevActions.at(0);
        const isMultipleChildMoneyRequests = (lastAction?.childMoneyRequestCount ?? 0) > 1;
        return lastAction?.reportActionID !== lastPrevVisibleAction?.reportActionID || isMultipleChildMoneyRequests;
}, [prevSortedVisibleReportActionsObjects, lastAction]);

What specific scenarios should we cover in automated tests to prevent reintroducing this issue in the future?

N/A

What alternative solutions did you explore? (Optional)

POC

Screen.Recording.2025-01-24.at.8.12.51.PM.mov

[rlinoz]

But I mean, shouldn't lastAction?.reportActionID get updated?

Also, it looks related to this PR as was pointed out in the slack thread #54071