perf: Migrate to Flashlist in MoneyRequestReportTransactionList by TMisiukiewicz · Pull Request #91422 · Expensify/App

TMisiukiewicz · 2026-05-22T11:58:02Z

Explanation of Change

Problem
On heavy money-request reports the RHP list was effectively non-virtualised. The inner transactions section was rendered via plain .map() inside the parent FlatList's ListHeaderComponent, which renders eagerly. Every transaction row mounted synchronously when the report opened, pushing report open time to ~20–30s for a report with 1600 expenses and producing a noticeable jank window on every navigation.

Solution

Unified list — merged the inner transactions section and the outer report-actions section into a single virtualised list. A discriminated-union UnifiedListItem (section-header | transaction | transactions-footer | report-action) flows through one renderItem dispatcher, so transactions and chat messages now share the same recycler window instead of one being eagerly rendered inside the other's header.
FlashList — migrated the list from react-native's FlatList (FlatListWithScrollKey). initialScrollIndex replaces the FlatList-specific useFlatListScrollKey wrapper
Controller + sub-component — MoneyRequestReportTransactionList continues to own the transaction-domain state (sort, group-by, selection, columns, totals, etc.) and exposes it to the parent via a render-prop controller. The parent renders a small MoneyRequestReportUnifiedList sub-component that assembles the FlashList from controller data plus the report-actions list

Fixed Issues

$ #91425
PROPOSAL:

Tests

Go to Spend tab
Go to Reports tab
Open Report with a couple of expenses - where list is not scrollable
Verify everything is displayed correctly
Open Report with a lot of expenses in multiple categories
Verify report opens correctly
Select a single report and verify it selects correctly
Select all reports from a category using category header and verify they are all selected (even if they are out of the viewport)
Select all reports from all categories using top table header and verify all reports in a list get selected
Send a message on the report and verify you are scrolled to the bottom of the list
Web only: Narrow down the viewport horizontally and verify the table is scrollable horizontally

Verify that no errors appear in the JS console

Offline tests

N/A

QA Steps

Same as tests

Verify that no errors appear in the JS console

PR Author Checklist

Screenshots/Videos

Android: Native

Android: mWeb Chrome

iOS: Native

ios.mov

iOS: mWeb Safari

MacOS: Chrome / Safari

web.mov

…rt-list

…ation

codecov · 2026-05-22T12:13:37Z

Codecov Report

❌ Looks like you've decreased code coverage for some files. Please write tests to increase, or at least maintain, the existing level of code coverage. See our documentation here for how to interpret this table.

Files with missing lines	Coverage Δ
...ew/MoneyRequestReportTransactionLongPressModal.tsx	`0.00% <0.00%> (ø)`
...View/MoneyRequestReportHorizontalScrollWrapper.tsx	`0.00% <0.00%> (ø)`
...stReportView/MoneyRequestReportTransactionList.tsx	`0.32% <0.00%> (+<0.01%)`	⬆️
...equestReportView/MoneyRequestReportActionsList.tsx	`53.65% <19.40%> (-11.13%)`	⬇️
... and 13 files with indirect coverage changes

…onents

…rt-list

melvin-bot · 2026-05-26T07:20:10Z

@aimane-chnaif 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]

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aimane-chnaif · 2026-05-26T09:54:44Z

Reviewer Checklist

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Screenshots/Videos

Android: HybridApp

Android: mWeb Chrome

iOS: HybridApp

iOS: mWeb Safari

MacOS: Chrome / Safari

Copilot

Pull request overview

Note

Copilot was unable to run its full agentic suite in this review.

Migrates the Money Request report view to a single unified, virtualized list (FlashList) so transaction rows are no longer eagerly rendered inside a header, improving open-time and scroll performance on large reports.

Changes:

Introduced a controller/render-prop in MoneyRequestReportTransactionList to provide transaction UI + items for a unified parent list.
Replaced the report actions FlatList with a FlashList that interleaves transactions, a transactions footer, and report actions in one dataset.
Added dedicated components for horizontal scroll restoration and the transaction long-press selection modal.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 6 comments.

File	Description
src/components/MoneyRequestReportView/MoneyRequestReportTransactionLongPressModal.tsx	Adds an imperative long-press modal to enter selection mode and select a transaction.
src/components/MoneyRequestReportView/MoneyRequestReportTransactionList.tsx	Refactors transaction list into a controller that supplies items + chrome for a unified parent FlashList.
src/components/MoneyRequestReportView/MoneyRequestReportHorizontalScrollWrapper.tsx	Extracts horizontal scroll + offset restoration logic for wide table layouts.
src/components/MoneyRequestReportView/MoneyRequestReportActionsList.tsx	Builds the unified FlashList (transactions + footer + report actions) and wires viewability/scroll behaviors.

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aimane-chnaif · 2026-05-26T11:48:15Z

+                                visibleReportActions={visibleReportActions}
+                                renderReportAction={renderReportAction}
+                                linkedReportActionID={linkedReportActionID}
+                                listRef={reportScrollManager.ref as unknown as React.Ref<FlashListRef<UnifiedListItem>>}


Can we improve this typing? This typecast is not preferred.

The cast reflects an architectural seam - the shared ActionListContext was built around FlatList, but this screen uses FlashList. The runtime types are compatible (same scroll methods), but properly removing the cast requires reshaping the shared context, which would touch a lot of other files that are not relevant to this migration. Do you think we can leave it as-is here?

Sure. This kind of issues can be always follow-up.

aimane-chnaif · 2026-05-26T12:14:44Z

I noticed several issues but only reporting the regressions not happening in production.

Bug: Tapping "Latest message" badge doesn't jump to latest message

Screen.Recording.2026-05-26.at.1.08.18.PM.mov

Bug: While scrolling fast, empty content briefly shows (Tested on 40 expenses)

Screen.Recording.2026-05-26.at.12.57.14.PM.mov

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chatgpt-codex-connector · 2026-05-26T12:23:26Z

+                initialScrollIndex={initialScrollIndex}
+                onViewableItemsChanged={onViewableItemsChangedAdjusted}


Preserve linked action anchoring when opening a report

Replacing initialScrollKey behavior with plain initialScrollIndex in MoneyRequestReportUnifiedList can break deep-link/open-at-action flows for long reports: initialScrollIndex is only an initial mount hint, so once pagination/backfill mutates data (and this list has a large dynamic ListHeaderComponent), the linked action is no longer reliably anchored and users can land away from the targeted message. The previous list wrapper handled key-based anchoring across data expansion; this version computes a one-time index and does not provide a stable post-mount anchor path.

Useful? React with 👍 / 👎.

TMisiukiewicz · 2026-05-26T13:43:50Z

Investigating the reported bugs ⌛

…rt-list

TMisiukiewicz · 2026-05-26T13:48:06Z

@mountiny could you run an adhoc to verify if empty cells bug is development only

…rt-list

github-actions · 2026-05-27T09:31:02Z

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

…rt-list

github-actions · 2026-05-27T16:43:00Z

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

github-actions · 2026-05-27T16:50:41Z

🧪🧪 Use the links below to test this adhoc build on Android, iOS, and Web. Happy testing! 🧪🧪
Built from App PR #91422.

Android 🤖	iOS 🍎
https://ad-hoc-expensify-cash.s3.us-east-1.amazonaws.com/rock-artifacts/ad-hoc/rock-android-Adhoc-aea7de094c3-4205783-e3da9a99b9a526bb1b45607ea67788b5dffb07ee/index.html	https://ad-hoc-expensify-cash.s3.us-east-1.amazonaws.com/rock-artifacts/ad-hoc/rock-ios-device-AdHoc-aea7de0-4205783-f18fc8f5219db102fdc71b0636a56440bd86196a/index.html

Web 🕸️
https://91422.pr-testing.expensify.com

👀 View the workflow run that generated this build 👀

melvin-bot Bot assigned TMisiukiewicz May 22, 2026

TMisiukiewicz added 3 commits May 22, 2026 14:00

Merge remote-tracking branch 'origin/main' into perf/virtualised-repo…

4b12b1a

…rt-list

perf: migrate transaction list from .map() to FlashList for virtualiz…

4551621

…ation

perf: unify transactions + actions into one virtualised list

f68b1ee

fix: restore lastTransactionID and isDesktopTableLayout

d64ff24

mountiny mentioned this pull request May 22, 2026

perf: virtualise transaction list in report screen #91425

Open

TMisiukiewicz added 8 commits May 25, 2026 09:14

fix: CI spellcheck and remove memoization wrappers

f4fbe38

fix: rephrase virtualized comment to satisfy cspell

1ee223b

use Flashlist

52ceec0

refactor: extract unified list render-prop body into sub-component

2779f70

fix: hoist long-press modal out of virtualised footer cell

71af131

Merge branch 'main' into perf/virtualised-report-list

81bb0f0

refactor: extract long-press modal and horizontal scroll wrapper comp…

1220e39

…onents

Merge remote-tracking branch 'origin/main' into perf/virtualised-repo…

6b5c9be

…rt-list

TMisiukiewicz changed the title ~~perf: virtualise transaction list in report screen~~ perf: Migrate to Flashlist in MoneyRequestReportTransactionList May 26, 2026

TMisiukiewicz marked this pull request as ready for review May 26, 2026 07:20

TMisiukiewicz requested review from a team as code owners May 26, 2026 07:20

melvin-bot Bot requested review from aimane-chnaif and joekaufmanexpensify and removed request for a team and joekaufmanexpensify May 26, 2026 07:20

github-actions Bot reviewed May 26, 2026

View reviewed changes

Comment thread src/components/MoneyRequestReportView/MoneyRequestReportTransactionList.tsx Outdated

github-actions Bot reviewed May 26, 2026

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Comment thread src/components/MoneyRequestReportView/MoneyRequestReportActionsList.tsx

chatgpt-codex-connector Bot reviewed May 26, 2026

View reviewed changes

Comment thread src/components/MoneyRequestReportView/MoneyRequestReportActionsList.tsx Outdated

TMisiukiewicz added 2 commits May 26, 2026 11:37

remove dead keyExtractor from transaction list controller

143946e

fix unread marker index offset when transactions are present

03ce297

mountiny requested review from Copilot and mountiny May 26, 2026 11:34

Copilot AI reviewed May 26, 2026

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aimane-chnaif reviewed May 26, 2026

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chatgpt-codex-connector Bot reviewed May 26, 2026

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avoid scanning transactions when resolving linked action index

4af0be0

Merge remote-tracking branch 'origin/main' into perf/virtualised-repo…

2a930b8

…rt-list

TMisiukiewicz added 2 commits May 27, 2026 08:29

Merge remote-tracking branch 'origin/main' into perf/virtualised-repo…

27b98dd

…rt-list

Pin scroll to bottom while deferred report items hydrate

e58e95c

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TMisiukiewicz added 2 commits May 27, 2026 12:32

Merge remote-tracking branch 'origin/main' into perf/virtualised-repo…

c89d0da

…rt-list

Merge remote-tracking branch 'origin/main' into perf/virtualised-repo…

aea7de0

…rt-list

		initialScrollIndex={initialScrollIndex}
		onViewableItemsChanged={onViewableItemsChangedAdjusted}

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