Order details: Fix crash when reloading orders

[itsmeichigo]

Closes WOOMOB-604

Description

Previously, there was an attempt to fix the crash when reloading the order details screen. This mitigated some of the cases but the same crash still happens sometimes after refunding a cached order and reloading the same order.

The crash is due to the use of computed variables in OrderDetailsDataSource. For the case with refunding, the app would crash in the following scenario:

• User opens the order details screen or pulls to refresh the screen.
• OrderDetailsDataSource determines the sections in reloadSections.
• Refunds are loaded and synced in to the local storage asynchronously.
• The table view reloads data and configures the order items section, but the aggregateOrderItems computed property returns an empty array due to the refund. => The app crashes when configuring order items with index out of bounds error.

The solution is to freeze all access to the results controllers upon reloadSections to avoid discrepancies when reloading data.

Testing steps

1. Create an order and fulfill it.
2. Open the order on the app to ensure that it's cached into local storage.
3. Refund the same order on the web or on another device.
4. Back to the app, pull to refresh the order details screen.
5. Confirm that the app doesn't crash. The order details should display the correct details.

Since the crash happens depending on the timing of the refund syncing, so ensure to do a few tries to confirm.

Testing information

Tested and confirmed the fix on simulator iPhone 16 iOS 18.4

Screenshots

https://github.com/user-attachments/assets/0da15bb7-0b8f-46b6-87fb-03449bc8a16f

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• [x] I have considered if this change warrants user-facing release notes and have added them to RELEASE-NOTES.txt if necessary.

[wpmobilebot]

📲 You can test the changes from this Pull Request in WooCommerce iOS Prototype by scanning the QR code below to install the corresponding build.

	App Name	WooCommerce iOS Prototype
	Build Number	30577
	Version	PR #15764
	Bundle ID	com.automattic.alpha.woocommerce
	Commit	1737b8e8eac448e464f06337259fb3400bf6e1b2
	Installation URL	36dbp7fdcohp8

Automatticians: You can use our internal self-serve MC tool to give yourself access to those builds if needed.

[itsmeichigo]

@RafaelKayumov Regarding your suggestion:

But it feels like those methods should be coupled with the reloadSections()

I think the purpose is to decouple the logic, as the calls are triggered from the higher in the hierarchy: OrderDetailsViewController > OrderDetailsViewModel > OrderDetailsDatasource > OrderDetailsResultsControllers.

The view controllers triggers table view reload when there's a change to the order object:

https://github.com/woocommerce/woocommerce-ios/blob/c8788efc3e4aa44e1786c981923218582b06cf53/WooCommerce/Classes/ViewRelated/Orders/Order%20Details/OrderDetailsViewController.swift#L204-L212

The view controller also triggers table view reload upon results controller updates:

https://github.com/woocommerce/woocommerce-ios/blob/c8788efc3e4aa44e1786c981923218582b06cf53/WooCommerce/Classes/ViewRelated/Orders/Order%20Details/OrderDetailsViewController.swift#L219-L221

Also the lookUpProductVariation(...) relies on readonly value taken from resultsControllers.productVariations which is a fetched property and can potentially vary as a result of a race condition.

Good catch! Moved product variations to a property in dc7f0dc6aba19a41a6e62f00a96e695bfed984d6.

[itsmeichigo]

Thanks for taking a look @jaclync.

Just checking the code changes. Is the crash reproducible before this PR? Are the repro steps different from https://github.com/woocommerce/woocommerce-ios/pull/15633 previously? If so, I wonder why it was fixed back then but not anymore.

The issue back then was 100% reproducible. The issue this PR is trying to address is more of a timing issue. The app crashes only when the refund update comes in the middle of a reload.

I responded to your other questions in the corresponding threads.