refactor: Improve and simplify attachment and file validation

[chrispader]

@mountiny @parasharrajat

Explanation of Change

This extracts some of the changes to attachment validation made in #69523.

Fixed Issues

$ #53493
PROPOSAL:

Tests

• Verify that no errors appear in the JS console

1. Open the app and go to a report
2. Drop different types of files into the dual drop zone or paste into composer
3. Make sure that proper validation and downsizing/file conversion is handled.

Offline tests

None needed.

QA Steps

• Verify that no errors appear in the JS console

Same as in Tests.

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
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    • 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:
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  • 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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• 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)
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• 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.
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  • I verified that all the inputs inside a form are aligned with each other.
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• 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: mWeb Chrome

iOS: Native

iOS: mWeb Safari

MacOS: Chrome / Safari

MacOS: Desktop

[mountiny]

Nice! thanks!

[melvin-bot]

@cristipaval 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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[joekaufmanexpensify]

No product review needed

[parasharrajat]

Screenshots

🔲 iOS / native

🔲 iOS / Safari

🔲 MacOS / Chrome

🔲 Android / Chrome

🔲 Android / native

[mountiny]

@parasharrajat seems like ready for your review again

[chrispader]

@parasharrajat as mentioned in #84423 (comment), this PR is going to fix some of the issues that you mentioned in #84423 and that are also reproducible on main.

Here' is a recording of the same flow, that was failing in #84423, but works just fine in this PR:

Screen.Recording.2026-03-09.at.12.45.10.mov

[parasharrajat]

BUG: Web: Are able to load corrupted PDF

[parasharrajat]

BUG: Web: Add attachment modal show forever loader when we are uploading 104 MB vid.

So it seems that vid shows after some time, may it was downsizing but when I sent this as a comment. we receive backend error.

[parasharrajat]

BUG: web: I am able to send json/video file as a receipt via drag and drop.

[parasharrajat]

Overall, it seems that validations are not working across attachment and receipts.

[chrispader]

@parasharrajat i'm checking again!

[chrispader]

@parasharrajat i made a bunch of changes and now the validation works smoothly. Note that the AttachmentPicker component displays an alert if the image dimensions are too big. This is also reproducible on main, therefore i did not change or fix this.

In a follow-up, we might want to integrate this error message into the collected errors in useFilesValidation

Here's a screen recording including multiple PDFs, images, HEIC files, large images to resize, videos:

validation.webm