Preserve GPS distance properties when reverting a split expense

[MelvinBot]

Explanation of Change

When a GPS distance split is reverted (by deleting one of the splits), the optimistic transaction created during the revert was missing commentType and customUnit properties. This happened because the reverse split path in Split.ts sets existingTransaction to undefined, causing buildOptimisticTransaction to skip setting comment.type to CUSTOM_UNIT and comment.customUnit. Without these properties, isDistanceRequest() and isGPSDistanceRequest() return false, making the Distance and Amount fields incorrectly editable.

Two changes fix this:

1. Pass commentType from the original transaction through the reverse split path (matching the existing pattern in the edit draft path).
2. Broaden the customUnit setup condition in buildOptimisticTransaction to also enter the block when customUnit is explicitly provided as a parameter, even without an existingTransaction.

Fixed Issues

$ #82635
PROPOSAL: #82635 (comment)

Tests

1. Log in with an Expensifail account.
2. Create a GPS distance expense in a workspace chat.
3. Open the GPS distance expense and verify the Distance field is disabled.
4. Tap More > Split > Save.
5. Open any split and verify the Distance field is still disabled.
6. Tap More > Delete > Delete to revert the split.
7. Verify the Distance field remains disabled after the revert.

• Verify that no errors appear in the JS console

Offline tests

1. Create a GPS distance expense in a workspace chat while online.
2. Go offline.
3. Split the expense, then delete one of the splits to revert.
4. Verify the Distance field remains disabled after the revert.
5. Go back online and verify the transaction syncs correctly.

QA Steps

1. Log in with an Expensifail account.
2. Create a GPS distance expense in a workspace chat.
3. Open the GPS distance expense and verify the Distance field is disabled.
4. Tap More > Split > Save.
5. Open any split and verify the Distance field is still disabled.
6. Tap More > Delete > Delete to revert the split.
7. Verify the Distance field remains disabled after the revert.

• 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
• 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 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)
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  • 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.
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  • The assets load correctly across all supported platforms.
• 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)
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• 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: mWeb Chrome

iOS: Native

iOS: mWeb Safari

MacOS: Chrome / Safari

[MelvinBot]

I created this PR from an upstream branch since I don't have push access to your fork.

To take ownership of this branch and be able to push updates, run:

git remote add upstream https://github.com/Expensify/App.git
git fetch upstream claude-fixGPSDistanceFieldAfterRevertSplit
git checkout -b claude-fixGPSDistanceFieldAfterRevertSplit upstream/claude-fixGPSDistanceFieldAfterRevertSplit
git push -u origin claude-fixGPSDistanceFieldAfterRevertSplit

Then you can close this PR and open a new one from your fork.

[MelvinBot]

The failing check (ESLint check) is unrelated to this PR.

Analysis: The full-repo ESLint check is failing with 336 warnings (0 errors) in files not touched by this PR. The "Changed files ESLint check" (which only lints files modified in this PR) passes successfully.

The warnings are in these unrelated files:

• src/pages/workspace/travel/WorkspaceTravelInvoicingExportPage.tsx — react-hooks/set-state-in-effect
• src/pages/workspace/upgrade/WorkspaceUpgradePage.tsx — react-hooks/preserve-manual-memoization
• src/pages/workspace/workflows/approvals/WorkspaceWorkflowsApprovalsEditPage.tsx — react-hooks/set-state-in-effect
• src/pages/workspace/workflows/approvals/WorkspaceWorkflowsApprovalsExpensesFromPage.tsx — react-hooks/set-state-in-effect

Evidence: This PR only modifies src/libs/TransactionUtils/index.ts, src/libs/actions/IOU/Split.ts, and src/libs/actions/IOU/index.ts — none of which appear in the ESLint warnings. This is a pre-existing issue on main.

[codecov]

Codecov Report

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

Files with missing lines	Coverage Δ
src/libs/TransactionUtils/index.ts	83.15% <100.00%> (ø)
src/libs/actions/IOU/Split.ts	77.65% <ø> (ø)
src/libs/actions/IOU/index.ts	74.07% <ø> (ø)
... and 26 files with indirect coverage changes

[rojiphil]

@MelvinBot Close this PR as the issue is no longer reproducible

[MelvinBot]

Closing this PR as requested by rojiphil — the linked issue is no longer reproducible.