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Fix - Viewport does not return to highlighted message after returning from thread#67752

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Valforte merged 11 commits intoExpensify:mainfrom
dmkt9:fix/61550
Sep 10, 2025
Merged

Fix - Viewport does not return to highlighted message after returning from thread#67752
Valforte merged 11 commits intoExpensify:mainfrom
dmkt9:fix/61550

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@dmkt9 dmkt9 commented Aug 4, 2025

Explanation of Change

Fixed Issues

$ #61550
PROPOSAL: #61550 (comment)

Tests

Same as QA Steps

  • Verify that no errors appear in the JS console

Offline tests

Same as QA Steps

QA Steps

  1. Go to staging.new.expensify.com
  2. Go to workspace chat.
  3. Submit at least two expenses.
  4. Go to expense report.
  5. Send many messages until the chat is scrollable
  6. Right click on the newest message > Reply in thread.
  7. Click on the link under header subtitle.
  8. The viewport will return to the highlighted message (the same way it behaves when returning from thread).
  • Verify that no errors appear in the JS console

PR Author Checklist

  • I linked the correct issue in the ### Fixed Issues section above
  • I wrote clear testing steps that cover the changes made in this PR
    • I added steps for local testing in the Tests section
    • I added steps for the expected offline behavior in the Offline steps section
    • I added steps for Staging and/or Production testing in the QA steps section
    • I added steps to cover failure scenarios (i.e. verify an input displays the correct error message if the entered data is not correct)
    • I turned off my network connection and tested it while offline to ensure it matches the expected behavior (i.e. verify the default avatar icon is displayed if app is offline)
    • I tested this PR with a High Traffic account against the staging or production API to ensure there are no regressions (e.g. long loading states that impact usability).
  • I included screenshots or videos for tests on all platforms
  • I ran the tests on all platforms & verified they passed on:
    • Android: Native
    • Android: mWeb Chrome
    • iOS: Native
    • iOS: mWeb Safari
    • MacOS: Chrome / Safari
    • MacOS: Desktop
  • I verified there are no console errors (if there's a console error not related to the PR, report it or open an issue for it to be fixed)
  • I verified there are no new alerts related to the canBeMissing param for useOnyx
  • I followed proper code patterns (see Reviewing the code)
    • I verified that any callback methods that were added or modified are named for what the method does and never what callback they handle (i.e. toggleReport and not onIconClick)
    • I verified that comments were added to code that is not self explanatory
    • I verified that any new or modified comments were clear, correct English, and explained "why" the code was doing something instead of only explaining "what" the code was doing.
    • I verified any copy / text shown in the product is localized by adding it to src/languages/* files and using the translation method
      • If any non-english text was added/modified, I used JaimeGPT to get English > Spanish translation. I then posted it in #expensify-open-source and it was approved by an internal Expensify engineer. Link to Slack message:
    • I verified all numbers, amounts, dates and phone numbers shown in the product are using the localization methods
    • I verified any copy / text that was added to the app is grammatically correct in English. It adheres to proper capitalization guidelines (note: only the first word of header/labels should be capitalized), and is either coming verbatim from figma or has been approved by marketing (in order to get marketing approval, ask the Bug Zero team member to add the Waiting for copy label to the issue)
    • I verified proper file naming conventions were followed for any new files or renamed files. All non-platform specific files are named after what they export and are not named "index.js". All platform-specific files are named for the platform the code supports as outlined in the README.
    • I verified the JSDocs style guidelines (in STYLE.md) were followed
  • If a new code pattern is added I verified it was agreed to be used by multiple Expensify engineers
  • I followed the guidelines as stated in the Review Guidelines
  • I tested other components that can be impacted by my changes (i.e. if the PR modifies a shared library or component like Avatar, I verified the components using Avatar are working as expected)
  • I verified all code is DRY (the PR doesn't include any logic written more than once, with the exception of tests)
  • I verified any variables that can be defined as constants (ie. in CONST.ts or at the top of the file that uses the constant) are defined as such
  • I verified that if a function's arguments changed that all usages have also been updated correctly
  • If any new file was added I verified that:
    • The file has a description of what it does and/or why is needed at the top of the file if the code is not self explanatory
  • If a new CSS style is added I verified that:
    • A similar style doesn't already exist
    • The style can't be created with an existing StyleUtils function (i.e. StyleUtils.getBackgroundAndBorderStyle(theme.componentBG))
  • If the PR modifies code that runs when editing or sending messages, I tested and verified there is no unexpected behavior for all supported markdown - URLs, single line code, code blocks, quotes, headings, bold, strikethrough, and italic.
  • If the PR modifies a generic component, I tested and verified that those changes do not break usages of that component in the rest of the App (i.e. if a shared library or component like Avatar is modified, I verified that Avatar is working as expected in all cases)
  • If the PR modifies a component related to any of the existing Storybook stories, I tested and verified all stories for that component are still working as expected.
  • If the PR modifies a component or page that can be accessed by a direct deeplink, I verified that the code functions as expected when the deeplink is used - from a logged in and logged out account.
  • If the PR modifies the UI (e.g. new buttons, new UI components, changing the padding/spacing/sizing, moving components, etc) or modifies the form input styles:
    • I verified that all the inputs inside a form are aligned with each other.
    • I added Design label and/or tagged @Expensify/design so the design team can review the changes.
  • If a new page is added, I verified it's using the ScrollView component to make it scrollable when more elements are added to the page.
  • I added unit tests for any new feature or bug fix in this PR to help automatically prevent regressions in this user flow.
  • If the main branch was merged into this PR after a review, I tested again and verified the outcome was still expected according to the Test steps.

Screenshots/Videos

Android: Native
android.native.mp4
Android: mWeb Chrome
android.mweb.chrome.mp4
iOS: Native
ios.native.mp4
iOS: mWeb Safari
ios.safari.mp4
MacOS: Chrome / Safari
mac.safari.mp4
MacOS: Desktop
mac.desktop.mp4

@dmkt9 dmkt9 requested a review from a team as a code owner August 4, 2025 11:57
@melvin-bot melvin-bot bot requested a review from dominictb August 4, 2025 11:57
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melvin-bot bot commented Aug 4, 2025

@dominictb 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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@dmkt9 We have conflicts.

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BUG: List jumps when going back from thread of a message that is closer to top (this does not happen on production):

Screen.Recording.2025-08-07.at.01.15.56.mov

Same thing if the message is closer to the bottom. I think for the case of bottom, it already happens with the current inverted flat list so you might not need to fix it. But if you could, it would be much appreciated.

renderItem: ListRenderItem<T>;
};

function BaseFlatList<T>(props: BaseFlatListProps<T>, ref: ForwardedRef<RNFlatList>) {
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Suggested change
function BaseFlatList<T>(props: BaseFlatListProps<T>, ref: ForwardedRef<RNFlatList>) {
function FlatListWithScrollKey<T>(props: FlatListWithScrollKeyProps<T>, ref: ForwardedRef<RNFlatList>) {

shouldEnableAutoScrollToTopThreshold?: boolean;
renderItem: ListRenderItem<T>;
};

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Suggested change
/**
* FlatList component that handles initial scroll key.
*/

return data.slice(Math.max(0, currentDataIndex - (isInitialData ? 0 : getInitialPaginationSize)));
}
// If data.length > 1 and highlighted item is the last element, there will be a bug that does not trigger the `onStartReached` event.
// So we will need to return at least the last 2 elements in this case.
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Can it be more than 2?

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Yes, the value can be greater than 2. But returning 2 ensures that if the item height is large, the highlighted item remains in the visible viewport and covers the case where the data has only 2 items.

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dmkt9 commented Aug 7, 2025

BUG: List jumps when going back from thread of a message that is closer to top (this does not happen on production):

@dominictb This is what I expected. But actually when creating this PR I was quite worried because it creates unexpected jumps. However, this ensures that if ListHeaderComponent is too long, the method still works effectively:

// Since ListHeaderComponent is always prioritized for rendering before the data,
// it will be rendered once the data has finished loading.
// This prevents an unnecessary empty space above the highlighted item.
ListHeaderComponent={!initialScrollKey || (!!initialScrollKey && !isInitialData) ? ListHeaderComponent : undefined}

If we could know the exact height of the ListHeaderComponent and the message items, this would solve the problem for the inverted FlatList as well. However, it is quite difficult because their height is not fixed.

A video that lacks the logic mentioned above:

Screencast_20250807_085700.mp4

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dmkt9 commented Aug 7, 2025

@dominictb I am thinking of a solution that will create a loading state when rendering FlatList and only show FlatList when rendering is complete. What do you think about this solution?

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The core benefit of FlatList is the progressive rendering, we should not show loading indicator then.

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dmkt9 commented Aug 7, 2025

The core benefit of FlatList is the progressive rendering, we should not show loading indicator then.

Thanks for the quick reply. I meant to only display it when FlatList first renders.

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dmkt9 commented Aug 7, 2025

@dominictb Here's a video of me trying out isInitialData && styles.opacity0 with a View wrapped around a FlatList:

Screencast_20250807_094325.mp4

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@dmkt9 Can you try with Android native? Slower animation might have visualize it better.

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dmkt9 commented Aug 7, 2025

@dmkt9 Can you try with Android native? Slower animation might have visualize it better.

@dominictb On mobile devices, I don't see this issue. It seems that due to the transition animation, the component is fully rendered while the animation is playing.

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BUG: App opens the middle of the list when returning from thread on native

Screen.Recording.2025-08-12.at.21.06.19-compressed.mov

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BUG: It always has a top offset of 1 message:

Screen.Recording.2025-08-12.at.21.13.42-compressed.mov

For inverted flat list, the highlighted message is always at the bottom. So I expect normal flat list should pin it as the top message.

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dmkt9 commented Aug 13, 2025

BUG: It always has a top offset of 1 message:

Oh. Thanks. My bad. I refactored displayedData but forgot to add the last element check.

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dmkt9 commented Aug 13, 2025

BUG: App opens the middle of the list when returning from thread on native

I just checked on Android but it works fine. I don't have my iOS device with me right now, I will check again tomorrow.

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@dmkt9 How's it going?

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dmkt9 commented Aug 15, 2025

@dmkt9 How's it going?

@dominictb Thanks for your reminder. My mac has some problems. I will update as soon as possible.

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dmkt9 commented Aug 16, 2025

@dominictb Thanks for your patience. I've updated the PR to address the iOS issues.

ios.test.result.mp4

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BUG: Message does not pin at the bottom in inverted flat list

Screen.Recording.2025-08-22.at.07.24.51.mov

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BUG: List jumps when returning from thread:

Screen.Recording.2025-08-22.at.07.25.26-compressed.mov

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dmkt9 commented Aug 22, 2025

BUG: Message does not pin at the bottom in inverted flat list

Our PR doesn't affect the inverted FlatList, so it's not the cause of the issue. There's a separate issue tracking it.

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dmkt9 commented Aug 22, 2025

BUG: List jumps when returning from thread:

Thanks for your review. This is my solution to address the bug on iOS. The bug is caused by a specific mechanism unique to iOS.

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BUG: List does not scroll to bottom on pressing new message indicator:

Screen.Recording.2025-09-03.at.07.09.40.mov

Comment on lines 58 to 59
// eslint-disable-next-line react-compiler/react-compiler
// eslint-disable-next-line react-hooks/exhaustive-deps
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// eslint-disable-next-line react-compiler/react-compiler
// eslint-disable-next-line react-hooks/exhaustive-deps
// eslint-disable-next-line react-compiler/react-compiler, react-hooks/exhaustive-deps

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Resolved

*/
const initialNumToRender = useMemo((): number | undefined => {
const minimumReportActionHeight = styles.chatItem.paddingTop + styles.chatItem.paddingBottom + variables.fontSizeNormalHeight;
const availableHeight = windowHeight - (CONST.CHAT_FOOTER_MIN_HEIGHT + variables.contentHeaderHeight);
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This does not account for the list header component here, right?

ListHeaderComponent={
<>
<MoneyRequestViewReportFields
report={report}
policy={policy}
/>
<MoneyRequestReportTransactionList

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@dominictb Sorry for the delay. Yes. However, since we only render the ListHeaderComponent after the initial render is complete, it's not really necessary to calculate its height.

The method for determining initialNumToRender is based on the approach used in ReportActionsList.

/**
* Calculates the ideal number of report actions to render in the first render, based on the screen height and on
* the height of the smallest report action possible.
*/
const initialNumToRender = useMemo((): number | undefined => {
const minimumReportActionHeight = styles.chatItem.paddingTop + styles.chatItem.paddingBottom + variables.fontSizeNormalHeight;
const availableHeight = windowHeight - (CONST.CHAT_FOOTER_MIN_HEIGHT + variables.contentHeaderHeight);
const numToRender = Math.ceil(availableHeight / minimumReportActionHeight);
if (linkedReportActionID) {
return getInitialNumToRender(numToRender);
}
return numToRender || undefined;
}, [styles.chatItem.paddingBottom, styles.chatItem.paddingTop, windowHeight, linkedReportActionID]);

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dmkt9 commented Sep 8, 2025

BUG: List does not scroll to bottom on pressing new message indicator:

@dominictb Hi, I’ve tried to reproduce it, but had no luck. However, our PR doesn’t touch the “New message” pill logic, so I don’t think it’s caused by our changes.

2025-09-08.17-52-03.mp4

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dominictb commented Sep 9, 2025

Reviewer Checklist

  • I have verified the author checklist is complete (all boxes are checked off).
  • I verified the correct issue is linked in the ### Fixed Issues section above
  • I verified testing steps are clear and they cover the changes made in this PR
    • I verified the steps for local testing are in the Tests section
    • I verified the steps for Staging and/or Production testing are in the QA steps section
    • I verified the steps cover any possible failure scenarios (i.e. verify an input displays the correct error message if the entered data is not correct)
    • I turned off my network connection and tested it while offline to ensure it matches the expected behavior (i.e. verify the default avatar icon is displayed if app is offline)
  • I checked that screenshots or videos are included for tests on all platforms
  • I included screenshots or videos for tests on all platforms
  • I verified that the composer does not automatically focus or open the keyboard on mobile unless explicitly intended. This includes checking that returning the app from the background does not unexpectedly open the keyboard.
  • I verified tests pass on all platforms & I tested again on:
    • Android: HybridApp
    • Android: mWeb Chrome
    • iOS: HybridApp
    • iOS: mWeb Safari
    • MacOS: Chrome / Safari
    • MacOS: Desktop
  • If there are any errors in the console that are unrelated to this PR, I either fixed them (preferred) or linked to where I reported them in Slack
  • I verified there are no new alerts related to the canBeMissing param for useOnyx
  • I verified proper code patterns were followed (see Reviewing the code)
    • I verified that any callback methods that were added or modified are named for what the method does and never what callback they handle (i.e. toggleReport and not onIconClick).
    • I verified that comments were added to code that is not self explanatory
    • I verified that any new or modified comments were clear, correct English, and explained "why" the code was doing something instead of only explaining "what" the code was doing.
    • I verified any copy / text shown in the product is localized by adding it to src/languages/* files and using the translation method
    • I verified all numbers, amounts, dates and phone numbers shown in the product are using the localization methods
    • I verified any copy / text that was added to the app is grammatically correct in English. It adheres to proper capitalization guidelines (note: only the first word of header/labels should be capitalized), and is either coming verbatim from figma or has been approved by marketing (in order to get marketing approval, ask the Bug Zero team member to add the Waiting for copy label to the issue)
    • I verified proper file naming conventions were followed for any new files or renamed files. All non-platform specific files are named after what they export and are not named "index.js". All platform-specific files are named for the platform the code supports as outlined in the README.
    • I verified the JSDocs style guidelines (in STYLE.md) were followed
  • If a new code pattern is added I verified it was agreed to be used by multiple Expensify engineers
  • I verified that this PR follows the guidelines as stated in the Review Guidelines
  • I verified other components that can be impacted by these changes have been tested, and I retested again (i.e. if the PR modifies a shared library or component like Avatar, I verified the components using Avatar have been tested & I retested again)
  • I verified all code is DRY (the PR doesn't include any logic written more than once, with the exception of tests)
  • I verified any variables that can be defined as constants (ie. in CONST.ts or at the top of the file that uses the constant) are defined as such
  • If a new component is created I verified that:
    • A similar component doesn't exist in the codebase
    • All props are defined accurately and each prop has a /** comment above it */
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    • The component has a clear name that is non-ambiguous and the purpose of the component can be inferred from the name alone
    • The only data being stored in the state is data necessary for rendering and nothing else
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  • If any new file was added I verified that:
    • The file has a description of what it does and/or why is needed at the top of the file if the code is not self explanatory
  • If a new CSS style is added I verified that:
    • A similar style doesn't already exist
    • The style can't be created with an existing StyleUtils function (i.e. StyleUtils.getBackgroundAndBorderStyle(theme.componentBG)
  • If the PR modifies code that runs when editing or sending messages, I tested and verified there is no unexpected behavior for all supported markdown - URLs, single line code, code blocks, quotes, headings, bold, strikethrough, and italic.
  • If the PR modifies a generic component, I tested and verified that those changes do not break usages of that component in the rest of the App (i.e. if a shared library or component like Avatar is modified, I verified that Avatar is working as expected in all cases)
  • If the PR modifies a component related to any of the existing Storybook stories, I tested and verified all stories for that component are still working as expected.
  • If the PR modifies a component or page that can be accessed by a direct deeplink, I verified that the code functions as expected when the deeplink is used - from a logged in and logged out account.
  • If the PR modifies the UI (e.g. new buttons, new UI components, changing the padding/spacing/sizing, moving components, etc) or modifies the form input styles:
    • I verified that all the inputs inside a form are aligned with each other.
    • I added Design label and/or tagged @Expensify/design so the design team can review the changes.
  • If a new page is added, I verified it's using the ScrollView component to make it scrollable when more elements are added to the page.
  • For any bug fix or new feature in this PR, I verified that sufficient unit tests are included to prevent regressions in this flow.
  • If the main branch was merged into this PR after a review, I tested again and verified the outcome was still expected according to the Test steps.
  • I have checked off every checkbox in the PR reviewer checklist, including those that don't apply to this PR.

Screenshots/Videos

Android: HybridApp
Screen.Recording.2025-09-09.at.16.49.18-compressed.mov
Android: mWeb Chrome
Screen.Recording.2025-09-09.at.16.38.31-compressed.mov
iOS: HybridApp
Screen.Recording.2025-09-09.at.16.30.14-compressed.mov
iOS: mWeb Safari
Screen.Recording.2025-09-09.at.16.32.51-compressed.mov
MacOS: Chrome / Safari
Screen.Recording.2025-09-09.at.16.27.53-compressed.mov
MacOS: Desktop
Screen.Recording.2025-09-09.at.16.31.56-compressed.mov

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Tests well. @dmkt9 Can you merge main one last time to make sure we won't break any thing?

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dmkt9 commented Sep 9, 2025

Tests well. @dmkt9 Can you merge main one last time to make sure we won't break any thing?

@dominictb Sure. I just merged it.

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Perf test is not related.

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LGTM. Thanks for the hard work but be mindful of potential regressions.

@melvin-bot melvin-bot bot requested a review from Valforte September 9, 2025 09:52
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LGTM

@Valforte Valforte merged commit d217e7e into Expensify:main Sep 10, 2025
20 of 21 checks passed
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✋ This PR was not deployed to staging yet because QA is ongoing. It will be automatically deployed to staging after the next production release.

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🚀 Deployed to staging by https://github.com/Valforte in version: 9.2.9-0 🚀

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

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🚀 Deployed to staging by https://github.com/Valforte in version: 9.2.11-0 🚀

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

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🚀 Deployed to production by https://github.com/francoisl in version: 9.2.12-4 🚀

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

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4 participants