[CP Staging] Fix hover highlight not working after sending a message by MelvinBot · Pull Request #88143 · Expensify/App

MelvinBot · 2026-04-16T18:04:14Z

Explanation of Change

Removes the if (lastScrollEvent.current) guard in useEmitComposerScrollEvents so the scroll-end timeout is always scheduled.

On the first scroll event, lastScrollEvent.current is null, so the guard prevented the SCROLLING: false timeout from being scheduled. After sending a message, the list auto-scrolls via a single scroll event — this hit the first-call bug and left SCROLLING stuck as true, which suppressed all hover highlights until the user manually scrolled (generating a second event that cleared the state).

This matches the pattern used in useScrollEventEmitter, which unconditionally schedules the timeout.

Fixed Issues

$ #88087
PROPOSAL: #88087 (comment)

Tests

Highlighted comments

Sign in to staging.new.expensify.com
Navigate to a conversation
Paste a text in compose box and send (copy a comment and paste in the compose box)
Hover over the comments in view
Comments should highlight when scrolled over

Offline testsSame as above

QA Steps

Same as above

PR Author Checklist

Screenshots/Videos

Android: Native

Android: mWeb Chrome

iOS: Native

iOS: mWeb Safari

MacOS: Chrome / Safari

When a single scroll event fires (e.g. auto-scroll after sending a message), the lastScrollEvent.current ref is null on the first call. The if guard prevented scheduling the SCROLLING:false timeout, leaving hover permanently suppressed. Removing the guard ensures the timeout is always scheduled, matching the pattern in useScrollEventEmitter. Co-authored-by: Jules <Julesssss@users.noreply.github.com>

situchan · 2026-04-16T18:06:32Z

            clearTimeout(scrollEndTimeout.current);
        }

-        if (lastScrollEvent.current) {


@MelvinBot can you find any side effects / regressions with this condition removal?

MelvinBot · 2026-04-16T18:09:55Z

The condition removal is safe — no side effects or regressions.

The if (lastScrollEvent.current) guard only prevented scheduling the scroll-end timeout on the very first scroll event. But that timeout would have executed correctly anyway: lastScrollEvent.current = timestamp is set synchronously on the very next line after setTimeout, so by the time the 250ms callback fires, the timestamp check passes and onScrollEnd() is called correctly.

The real guard against incorrect onScrollEnd() calls is the if (lastScrollEvent.current !== timestamp) check inside the timeout callback — that's what ensures only the most recent scroll event's timeout actually fires. Rapid scroll events are handled correctly too: each new event clears the previous timeout via clearTimeout.

This also makes useEmitComposerScrollEvents consistent with useScrollEventEmitter (index.ts:24-31), which has never had this guard.

Pre-existing note (unrelated to this PR)

useEmitComposerScrollEvents has no useEffect cleanup for scrollEndTimeout — if the component unmounts during the 250ms window, the timeout fires on a stale context. useScrollEventEmitter handles this correctly with a cleanup effect. Not introduced by this PR, but worth noting as a future improvement.

codecov · 2026-04-16T18:14:40Z

Codecov Report

✅ Changes either increased or maintained existing code coverage, great job!

Files with missing lines	Coverage Δ
src/hooks/useEmitComposerScrollEvents/index.ts	`0.00% <0.00%> (ø)`
... and 16 files with indirect coverage changes

melvin-bot · 2026-04-16T20:15:45Z

@situchan Please copy/paste the Reviewer Checklist from here into a new comment on this PR and complete it. If you have the K2 extension, you can simply click: [this button]

situchan · 2026-04-16T20:48:14Z

Reviewer Checklist

I have verified the author checklist is complete (all boxes are checked off).
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I verified tests pass on all platforms & I tested again on:
- Android: HybridApp
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Screenshots/Videos

Android: HybridApp

Android: mWeb Chrome

iOS: HybridApp

iOS: mWeb Safari

MacOS: Chrome / Safari

Screen.Recording.2026-04-17.at.2.47.32.AM.mov

MelvinBot · 2026-04-16T22:35:52Z

The only failing check is the PR Author Checklist — this is not a code issue. All CI checks (ESLint, typecheck, tests, builds, prettier, storybook, etc.) are passing. The checklist check requires manual action (reviewing and checking off the checklist items in the PR description).

MelvinBot · 2026-04-16T22:37:13Z

The only failing check is PR Author Checklist / checklist — this is not a code failure. All code checks (ESLint, typecheck, all 8 test jobs, builds, prettier, storybook, spellcheck) are passing.

The checklist check requires manual action (checking off items in the PR description) and cannot be fixed with a code change.

OSBotify · 2026-04-16T22:46:54Z

✋ This PR was not deployed to staging yet because QA is ongoing. It will be automatically deployed to staging after the next production release.

[CP Staging] Fix hover highlight not working after sending a message (cherry picked from commit f14c55a) (cherry-picked to staging by roryabraham)

github-actions · 2026-04-16T22:55:27Z

🚧 @mountiny has triggered a test Expensify/App build. You can view the workflow run here.

github-actions · 2026-04-16T23:00:28Z

🧪🧪 Use the links below to test this adhoc build on Android, iOS, and Web. Happy testing! 🧪🧪
Built from App PR #88143.

Android 🤖	iOS 🍎
https://ad-hoc-expensify-cash.s3.us-east-1.amazonaws.com/rock-artifacts/ad-hoc/rock-android-Adhoc-f14c55a-54c248e-ecd8add257585ca4ef5135983dbb82e3b9234233/index.html	https://ad-hoc-expensify-cash.s3.us-east-1.amazonaws.com/rock-artifacts/ad-hoc/rock-ios-device-AdHoc-f14c55a-54c248e-7458b42bff6fec445f0c1fd694e85bff683f3373/index.html

Web 🕸️
https://88143.pr-testing.expensify.com

👀 View the workflow run that generated this build 👀

OSBotify · 2026-04-16T23:21:18Z

🚀 Cherry-picked to staging by https://github.com/roryabraham in version: 9.3.60-11 🚀

platform	result
🕸 web 🕸	success ✅
🤖 android 🤖	success ✅
🍎 iOS 🍎	success ✅

Bundle Size Analysis (Sentry):

Android
iOS

MelvinBot · 2026-04-16T23:22:28Z

No help site changes are required for this PR.

This is a bug fix to internal scroll event handling (useEmitComposerScrollEvents) that removes a guard condition preventing the scroll-end timeout from being scheduled on the first scroll event. It doesn't change any user-facing features, settings, workflows, or terminology that would be documented in help site articles under App/docs/articles.

m-natarajan · 2026-04-17T01:04:16Z

PR pass, on Windows 11/ Chrome in v9.3.60-11

88143.mp4

OSBotify · 2026-04-17T03:25:59Z

🚀 Cherry-picked to staging by https://github.com/roryabraham in version: 9.3.60-12 🚀

platform	result
🕸 web 🕸	success ✅
🤖 android 🤖	success ✅
🍎 iOS 🍎	success ✅

Bundle Size Analysis (Sentry):

Android
iOS

MelvinBot · 2026-04-17T03:28:05Z

No help site changes are required for this PR.

This is an internal bug fix that removes a guard condition in the useEmitComposerScrollEvents hook so the scroll-end timeout is always scheduled. It fixes hover highlights not appearing after sending a message. The change doesn't affect any user-facing features, settings, workflows, or terminology that would be documented in help site articles under App/docs/articles.

OSBotify · 2026-04-21T11:15:24Z

🚀 Deployed to production by https://github.com/mountiny in version: 9.3.60-22 🚀

platform	result
🕸 web 🕸	success ✅
🤖 android 🤖	success ✅
🍎 iOS 🍎	success ✅

OSBotify · 2026-04-21T11:42:00Z

🚀 Cherry-picked to staging by https://github.com/roryabraham in version: 9.3.61-0 🚀

platform	result
🕸 web 🕸	success ✅
🤖 android 🤖	success ✅
🍎 iOS 🍎	success ✅

Bundle Size Analysis (Sentry):

Android
iOS

MelvinBot · 2026-04-21T11:43:06Z

No help site changes are required for this PR. The change is a purely internal bug fix to the useEmitComposerScrollEvents hook — it doesn't affect any user-facing features, settings, workflows, or terminology documented in the help site.

MelvinBot assigned Julesssss Apr 16, 2026

MelvinBot requested a review from a team April 16, 2026 18:04

MelvinBot mentioned this pull request Apr 16, 2026

[Due for payment 2026-04-28] Web - Comment/ expense not highlighted when hovered upon in a conversation after pasting #88087

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situchan reviewed Apr 16, 2026

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Julesssss marked this pull request as ready for review April 16, 2026 20:15

Julesssss requested a review from a team as a code owner April 16, 2026 20:15

melvin-bot Bot requested review from joekaufmanexpensify and situchan April 16, 2026 20:15

melvin-bot Bot removed request for a team April 16, 2026 20:15

situchan approved these changes Apr 16, 2026

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melvin-bot Bot requested a review from mollfpr April 16, 2026 20:48

mountiny approved these changes Apr 16, 2026

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mountiny changed the title ~~Fix hover highlight not working after sending a message~~ [CP Staging] Fix hover highlight not working after sending a message Apr 16, 2026

mountiny merged commit f14c55a into main Apr 16, 2026
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mountiny deleted the claude-fixHoverAfterSendMessage branch April 16, 2026 22:37

OSBotify added the CP Staging marks PRs that have been CP'd to staging label Apr 16, 2026

OSBotify mentioned this pull request Apr 16, 2026

Deploy Checklist: New Expensify 2026-04-16 #88022

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MelvinBot mentioned this pull request Apr 17, 2026

[Due for payment 2026-04-28] iOS-Self DM-App not scroll down after created the new expense in self DM #88174

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Explanation of Change

Fixed Issues

Tests

Offline testsSame as above

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