Chat - Scrolling does not work if the user adds a message or clicks 'New messages' button

[kbecciv]

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Version Number: 1.3.96.0
Reproducible in staging?: y
Reproducible in production?: n
If this was caught during regression testing, add the test name, ID and link from TestRail:
Email or phone of affected tester (no customers):
Logs: https://stackoverflow.com/c/expensify/questions/4856
Expensify/Expensify Issue URL:
Issue reported by: Applause - Internal Team
Slack conversation:

Action Performed:

1. Go to staging.new.expensify.com or open Desktop App
2. Login with any account and go to chat with long history
3. Scroll to the beginning of the chat
4. Post new messages > Check the result
5. Mark any message as unread and scroll up the chat until the "New messages" button appears
6. Click the "New messages" button > Check the result

Expected Result:

4. Message added and chat scrolled to new messages
5. Chat scrolled to new messages

Actual Result:

4. Message added and chat did not scroll to new messages
5. Chat did not scroll to new messages

Workaround:

Unknown

Platforms:

Which of our officially supported platforms is this issue occurring on?

• Android: Native
• Android: mWeb Chrome
• iOS: Native
• iOS: mWeb Safari
• MacOS: Chrome / Safari
• MacOS: Desktop

Screenshots/Videos

Bug6266738_1699321983202.Chat-Button-New-Message-scroll-not-working.mp4

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[OSBotify]

👋 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.

[melvin-bot]

Triggered auto assignment to @thienlnam (Engineering), see https://stackoverflow.com/c/expensify/questions/4319 for more details.

[thienlnam]

Hmm yeah, the 'New Message' indicator doesn't scroll me anymore

[situchan]

This came from custom ref handling in #28793
cc: @perunt @janicduplessis @thienlnam

[perunt]

If you press this button without navigating to thread would it scroll you down?

[situchan]

If you press this button without navigating to thread would it scroll you down?

Nope. Seems like ref of MVCPFlatList is not forwarded correctly

[situchan]

App/src/hooks/useReportScrollManager/index.ts

Lines 12 to 18 in a1a0f38

	const scrollToIndex = (index: number, isEditing?: boolean) => {
	if (!flatListRef?.current || isEditing) {
	return;
	}
	flatListRef.current.scrollToIndex({index, animated: true});
	};

Early returned because flatListRef.current is not set

[thienlnam]

@perunt You around to get a PR up for this? Ideally we can just fix the ref forwarding and then we won't have to revert the PR

[situchan]

There's another similar regression: #30935

[situchan]

Confirmed #30962 fixes this issue as well

[thienlnam]

Great - we'll link that one there then. Thanks for the help here!

[thienlnam]

This was taken care of in #30962