[WOOMOB-3229] Send image deletion when a variation image is removed

[irfano]

Fixes WOOMOB-3229

Description

Removing a variation's image never reached the store: the update mapper only included the image field when the new image was non-blank, so the removal was silently dropped and the image reappeared after the refresh. This was a regression from the bulk-create-variations refactor.

The mapper now sends image: {id: 0} when the image is cleared, which WooCommerce treats as deleting the variation image. Both variation fetches now use the REST edit context, GET wc/v3/products/<id>/variations/<id> for the edit screen and GET wc/v3/products/<id>/variations for the editing list, so the response carries the variation's own image instead of falling back to the parent product's image. This matches how the WooCommerce admin loads variations for editing: the variation's own image, or a placeholder. Other surfaces (the order creation variation picker and the POS lookup) keep the default view context, so the locally cached variation image carries the context of whichever fetch last wrote it. A null image in the response is now mapped to an empty string instead of the literal "null" it used to produce.

On stores older than WooCommerce 4.7, image removal isn't supported. The dedicated error message for this case was never actually shown due to a separate bug in its display condition; this PR fixes that too, so the app now shows it instead of a generic update error.

Test Steps

On a store with a variable product whose variation has an image:

1. Open the product's Variations list.
2. Open a variation that has an image.
3. Remove the variation image.
4. Tap Update.
5. Confirm the image placeholder is shown instead of the parent product's image.
6. Go back to the Variations list and confirm the row shows the placeholder too.
7. Reopen the variation and confirm the parent image doesn't flash before the placeholder.
8. Sanity-check that price, stock, and attributes still load correctly.

Images/gif

WooCommerce below 4.7 error message on removing a variation image.

• 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.

[claude]

AI Code Review - Found 1 potential issue

The core fix is sound and consistent end-to-end: a removed image maps to a blank WCProductVariationModel.image, the mapper now sends {"id":0} (WCProductImageModel.toJson correctly omits src/name for id 0), and the ViewModel's updated variation.image == null guard matches how removal is represented (Optional(null) → blank image). The isJsonNull guard in the API response and the ifEmpty refactor are correct. Good unit coverage on both the mapper and the ViewModel error path.

PR housekeeping

• This is the WooCommerce Android (Kotlin) repo; reviewed against AGENTS.md/CLAUDE.md FluxC + store-app conventions rather than the PHP/WooCommerce-core guidance.

---

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[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
	Build Number	772
	Version	25.2-rc-1
	Application ID	com.woocommerce.android.prealpha
	Commit	dbde534
	Installation URL	42ibuuo9q95co

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

[codecov-commenter]

Codecov Report

❌ Patch coverage is 7.69231% with 12 lines in your changes missing coverage. Please review.
✅ Project coverage is 41.16%. Comparing base (552970e) to head (355971f).

Files with missing lines	Patch %	Lines
...network/rest/wpcom/wc/product/ProductRestClient.kt	0.00%	4 Missing ⚠️
...rk/rest/wpcom/wc/product/ProductVariationMapper.kt	25.00%	1 Missing and 2 partials ⚠️
...st/wpcom/wc/product/ProductVariationApiResponse.kt	0.00%	2 Missing ⚠️
...rg/wordpress/android/fluxc/store/WCProductStore.kt	0.00%	2 Missing ⚠️
...ui/products/variations/VariationDetailViewModel.kt	0.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff            @@
##              trunk   #16245   +/-   ##
=========================================
  Coverage     41.15%   41.16%           
- Complexity    13501    13508    +7     
=========================================
  Files          2503     2503           
  Lines        146465   146468    +3     
  Branches      21761    21761           
=========================================
+ Hits          60278    60288   +10     
+ Misses        80089    80054   -35     
- Partials       6098     6126   +28     

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[AdamGrzybkowski]

LGTM 👍 but:

Both variation fetches now use the REST edit context, GET wc/v3/products//variations/ for the edit screen and GET wc/v3/products//variations for the editing list, so the response carries the variation's own image instead of falling back to the parent product's image.

I think it's worth confirming with the Peacock team because the fetchSingleVariation is also used by POS.

[dangermattic]

	1 Error
🚫	This PR is tagged with status: do not merge label(s).

Generated by 🚫 Danger

[irfano]

I think it's worth confirming with the Peacock team because the fetchSingleVariation is also used by POS.

Good point, Adam. This slightly changes the behavior of how variation images are displayed on the order details and POS screens. Also, this PR uses the existing image field in the DB, but populates it from two different sources (edit and view context fetches). I fixed that in a follow-up PR. I’ll merge this after the follow-up is approved, and I’ll ask Peacock to review the follow-up PR (#16272).