Navigate back to taxes list when tax detail RHN can't find tax

[allgandalf]

Explanation of Change

When a tax code is changed in OldDot while the tax detail RHN is open in NewDot, the page shows "Hmm it's not here" because the route param (taxID) becomes stale. The primary fix is on the backend (Expensify/Auth#20872) which adds previousTaxCode to the Pusher push so getCurrentTaxID() can resolve renamed taxes.

This PR adds a frontend fallback: if the tax can't be found and the policy has taxes loaded, navigate back to the taxes list instead of showing the not-found page. This handles edge cases like the brief race window or if the tax is deleted entirely.

Fixed Issues

$ #75052

Tests

1. Open a workspace with taxes enabled
2. Navigate to a tax detail page (click any tax)
3. In a second tab/OldDot, change that tax's code
4. Return to the NewDot tab
5. Verify the page navigates back to the taxes list instead of showing "Hmm it's not here"

• Verify that no errors appear in the JS console

Offline tests

1. Go offline
2. Navigate to a tax detail page
3. Verify the page still displays correctly (no redirect since Onyx data hasn't changed)

QA Steps

Same as tests

• 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).
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Screenshots/Videos

Screen.Recording.2026-04-09.at.8.40.38.AM.mov

[melvin-bot]

@eVoloshchak 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]

[codecov]

Codecov Report

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

Files with missing lines	Coverage Δ
src/pages/workspace/taxes/WorkspaceEditTaxPage.tsx	0.00% <0.00%> (ø)
... and 11 files with indirect coverage changes

[eVoloshchak]

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
• 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 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
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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

Android: mWeb Chrome

iOS: HybridApp

iOS: mWeb Safari

MacOS: Chrome / Safari

[allgandalf]

@eVoloshchak any updates on the review ?

[eVoloshchak]

@allgandalf, tests well on native and web, but on mWeb "Hmm it's not here" page is still visible for a split second during the navigation back

Screen.Recording.2026-04-10.at.09.46.17.mov

[allgandalf]

hmmm, i remember we faced similar bugs elsewhere before, do you know any possible solution ?

[eVoloshchak]

#85000 is the first that comes to mind.

When you open a report or expense, the App's "not found" detection logic (shouldShowNotFoundPage in ReportScreen) evaluates ​before​ the report data has finished loading from Onyx.

But here the cause is different, we show "Hmm it's not here" when loading is finished, but navigation animation is still in progress

We navigate away if there is no currentTaxRate, is there a case where currentTaxRate is null but we don't need to navigate the user away?

If no, I think we can simply return null here

[allgandalf]

@MelvinBot any solution to this #87175 (comment), how did we fix such issues previously

[MelvinBot]

The flash happens because the useEffect on line 61-66 runs after render, so the <NotFoundPage /> on line 77 paints first, then the redirect fires.

Fix: Move the redirect logic into the render phase. Instead of showing NotFoundPage when taxes are loaded but the specific tax is missing, return null (or a loading indicator) and let the useEffect navigate away. The key change is on line 76:

-    if (!currentTaxRate) {
-        return <NotFoundPage />;
+    if (!currentTaxRate) {
+        if (policy?.taxRates?.taxes) {
+            // Tax was removed/renamed — useEffect will navigate back; render nothing to avoid flash
+            return null;
+        }
+        return <NotFoundPage />;
     }

This way, when taxes are loaded but the specific tax is gone (the redirect case), nothing renders during the brief window before useEffect fires. NotFoundPage only shows when taxes genuinely haven't loaded at all.

Precedent in the codebase

Several places use this pattern:

• withReportOrNotFound.tsx (line 104-106): Returns null when content was previously shown but is now missing during navigation transitions (contentShown.current && !isFocused)
• AccessOrNotFoundWrapper.tsx (line 187-198): Uses Navigation.setNavigationActionToMicrotaskQueue() to defer navigation and avoid flash
• LinkedActionNotFoundGuard.tsx (line 80-107): Tracks hasSeenLoadingCycle state during render to prevent showing not-found when stale metadata exists before fresh data arrives

The common principle: don't render the not-found UI when you already know you're about to navigate away.