Snapshot picked files into memory-backed Files to prevent request queue poisoning

[elirangoshen]

Explanation of Change

On web, a File picked from disk (file picker, drag-and-drop) is only a lazy reference to its OS file. If the user modifies, deletes, renames, or moves that file after picking it but before the queued request is first persisted (for example while the attachment preview or the expense confirmation screen is open — whether by user action, a download still completing, or background software touching the file), the first IndexedDB write of the persisted request queue fails with:

DataError: Failed to write blobs (InvalidBlob)   (Windows)
DataError: Failed to write blobs (IOError)       (macOS)

The dead File then poisons networkRequestQueue: the storage write is retried 5×, and every subsequent queue rewrite re-serializes the same dead blob and fails again. Production logs show ~46k of these events over 3 days across AddAttachment, ReplaceReceipt, and RequestMoney (SmartScan) — all failing on the very first persist (retryAttempt: 0/5), which pins the failure to the pick → first-write window.

This PR snapshots the picked file's bytes into a memory-backed File in validateAttachmentFile (the single choke point all attachment/receipt flows go through via useFilesValidation). A memory-backed File cannot be invalidated by later disk changes, so the queued request always serializes. If the backing file is already unreadable at validation time, the user gets an immediate "file invalid" error instead of a silent failure later.

The snapshot lives in a platform-split module (src/libs/snapshotPickedFile/index.ts + index.native.ts): the web variant copies the bytes, the native variant keeps the existing rename-only behavior — native file objects never enter the IndexedDB blob path, and production logs show this error class exclusively from web user agents.

Related follow-up (independent, no dependency): Expensify/react-native-onyx#814 classifies this error as never-retriable at the storage layer, so any remaining inline File/Blob path fails once instead of retrying 5x. It ships separately via #96957.

Fixed Issues

$ #87844
$ #87871
PROPOSAL:

Tests

1. Run the web app in Chrome, sign in, and open DevTools console (enable the Verbose level).
2. Create a small image file on disk.
3. In a report, click the compose + → Add attachment and pick the file. Keep the preview modal open.
4. While the preview is open, delete (or overwrite) the file on disk.
5. Click Send.
6. Verify the attachment uploads successfully and the console shows no Failed to write blobs / [Onyx] Failed to save to storage errors.
7. Repeat steps 2–6 using the receipt scan flow (FAB → Create expense → Scan → choose the file, delete it on disk while on the confirmation screen, then submit). Verify the expense is created and no storage errors appear.
8. Run npx jest tests/unit/ValidateAttachmentFileTest.ts and verify all tests pass.

• Verify that no errors appear in the JS console

Offline tests

1. Enable Force offline (Settings → Troubleshoot).
2. Create a scan expense with a file picked from disk, then delete the file on disk.
3. Create a second (manual) expense so the persisted request queue is rewritten.
4. Verify no Failed to write blobs errors appear in the console.
5. Go back online and verify both expenses sync successfully.

QA Steps

Same as Tests (steps 1–7).

• 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 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 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)
• 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)
• 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 new assets were added or existing ones were modified, I verified that:
  • The assets are optimized and compressed (for SVG files, run npm run compress-svg)
  • 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)
• 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.
• 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

before

before.mov

after

after.mov

[github-actions]

⚠️ This PR is possibly changing native code and/or updating libraries, it may cause problems with HybridApp. Please check if any patch updates are required in the HybridApp repo and run an AdHoc build to verify that HybridApp will not break. Ask Contributor Plus for help if you are not sure how to handle this. ⚠️