[Woo POS] Fix variation lookup in WooPosProductsDataSource

[samiuelson]

WOOMOB-1573

Description

This PR removes dependency on WCProductStore from WooPosProductsRemoteDataSource::getVariationById. Instead of looking for variation in WCProductStore, it switches to in-memory variations cache used in POS, and falls back to the rest client in case the cache doesn't hold the variation.

Before, the getVariationById was using WCProductStore (used by store management) to get variation instance in POS Totals screen. This was incorrect, because the POS, in case local catalog is disabled, uses in-memory cache to render items, and WCProductStore is not really a good fit there because it is not synced in any way with the in-memory variations cache in POS.

Test Steps

1. Open a store not eligible for local catalog (e.g. 1000+ items)
2. Add variation items to Cart
3. Check out and collect payment

Smoke test POS, focusing on the Totals and Checkout screens.

Images/gif

N/A

• I have considered if this change warrants release notes and have added them to RELEASE-NOTES.txt if necessary. Use the "[Internal]" label for non-user-facing changes.

[Copilot]

Pull Request Overview

This PR adds enhanced caching logic for the getVariationById method in WooPosProductsRemoteDataSource. The implementation now checks the cache before making remote calls and refreshes the entire variation cache if a requested variation is not found but the cache already contains other variations for that product.

• Implements cache-first logic for variation retrieval
• Adds automatic cache refresh when variations exist but the requested one is not cached
• Returns null without remote call when cache is empty (indicating no variations exist)

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
WooPosProductsDataSource.kt	Implements new caching logic in getVariationById to check cache first, refresh from remote if variation not found but cache has variations, and return null for empty cache
WooPosProductsRemoteDataSourceTest.kt	Adds comprehensive test coverage for the new caching behavior including cache hit, cache miss with refresh, empty cache, error handling, and cache update scenarios

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[wpmobilebot]

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

	App Name	WooCommerce-Wear Android
	Platform	⌚️ Wear OS
	Flavor	Jalapeno
	Build Type	Debug
	Commit	3e41172
	Direct Download	woocommerce-wear-prototype-build-pr14918-3e41172.apk

[wpmobilebot]

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

	App Name	WooCommerce Android
	Platform	📱 Mobile
	Flavor	Jalapeno
	Build Type	Debug
	Commit	3e41172
	Direct Download	woocommerce-prototype-build-pr14918-3e41172.apk

[codecov-commenter]

Codecov Report

❌ Patch coverage is 92.85714% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 38.35%. Comparing base (3692a44) to head (3e41172).

Files with missing lines	Patch %	Lines
...os/home/items/products/WooPosProductsDataSource.kt	92.85%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##              trunk   #14918      +/-   ##
============================================
+ Coverage     38.33%   38.35%   +0.01%     
- Complexity    10146    10147       +1     
============================================
  Files          2145     2145              
  Lines        121313   121324      +11     
  Branches      16653    16656       +3     
============================================
+ Hits          46500    46528      +28     
+ Misses        70088    70070      -18     
- Partials       4725     4726       +1     

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