[HOLD for payment 2023-12-29] [$500] Android - Attachment - Application crashes when trying to scroll PDF preview

[kbecciv]

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Version Number: 1.4.14-2
Reproducible in staging?: y
Reproducible in production?: n
If this was caught during regression testing, add the test name, ID and link from TestRail:
Email or phone of affected tester (no customers):
Logs: https://stackoverflow.com/c/expensify/questions/4856
Expensify/Expensify Issue URL:
Issue reported by: Applause - Internal Team
Slack conversation:

Action Performed:

Prerequisites:
File for example https://drive.google.com/file/d/1a_8roG0lxsaBAWAo33pLSs8pAfN2nCY9/view?usp=drive_link
Steps:

1. Open New Expensify app
2. Log in under any account
3. Navigate to any conversation
4. Click on Compose Box - Add attachment
5. Add the PDF file from the example
6. Scroll PDF file in preview

Expected Result:

The application should not crash when you try to scroll through the PDF preview.

Actual Result:

Application crashes when trying to scroll PDF preview

Workaround:

Unknown

Platforms:

Which of our officially supported platforms is this issue occurring on?

• Android: Native
• Android: mWeb Chrome
• iOS: Native
• iOS: mWeb Safari
• MacOS: Chrome / Safari
• MacOS: Desktop

Screenshots/Videos

Add any screenshot/video evidence

Bug6321235_1703078349555.Record_2023-12-20-19-01-18.mp4

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[github-actions]

👋 Friendly reminder that deploy blockers are time-sensitive ⏱ issues! Check out the open `StagingDeployCash` deploy checklist to see the list of PRs included in this release, then work quickly to do one of the following:

1. Identify the pull request that introduced this issue and revert it.
2. Find someone who can quickly fix the issue.
3. Fix the issue yourself.

[melvin-bot]

Triggered auto assignment to @srikarparsi (Engineering), see https://stackoverflow.com/c/expensify/questions/4319 for more details.

[mkhutornyi]

Proposal

Please re-state the problem that we are trying to solve in this issue.

Android app crashes when scroll PDF in preview

What is the root cause of that problem?

Crash log:
ERROR ReanimatedError: Cannot read property 'shouldPagerScroll' of null, js engine: reanimated

So it happens on this line: attachmentCarouselPagerContext.shouldPagerScroll.value = (attachmentCarouselPagerContext is null)

App/src/components/Attachments/AttachmentView/AttachmentViewPdf/index.android.js

Lines 21 to 29 in f33d674

	if (offsetX.value !== 0 && offsetY.value !== 0) {
	// if the value of X is greater than Y and the pdf is not zoomed in,
	// enable the pager scroll so that the user
	// can swipe to the next attachment otherwise disable it.
	if (Math.abs(evt.allTouches[0].absoluteX - offsetX.value) > Math.abs(evt.allTouches[0].absoluteY - offsetY.value) && scaleRef.value === 1) {
	attachmentCarouselPagerContext.shouldPagerScroll.value = true;
	} else {
	attachmentCarouselPagerContext.shouldPagerScroll.value = false;
	}

What changes do you think we should make in order to solve the problem?

add null safety check
if (offsetX.value !== 0 && offsetY.value !== 0 && attachmentCarouselPagerContext) {

[srikarparsi]

Hey @mkhutornyi, are you available to work on this fix?

[mkhutornyi]

yes, I am

[srikarparsi]

Awesome, assigning you to the issue, can you create a PR and link it here?