Search Blocks: add pre-hydration skeleton to filter-wc-attribute

[Copilot]

filter-wc-attribute was the only bucket-driven filter block missing the shared pre-hydration skeleton plumbing. On a deep-linked URL (?pa_color[]=red), the attribute filter wrapper was hidden until JS hydration finished — showing a blank space instead of shimmer rows.

Why

WC attribute filters are typically the longest-loading filter region on a product page — one aggregation per registered pa_* taxonomy. The other bucket-driven filter blocks (filter-checkbox, filter-date, filter-wc-rating) already use the shared skeleton plumbing from #48505 / its follow-ups; this PR brings filter-wc-attribute to parity so deep-linked attribute filter URLs paint the same shimmer rows on first paint instead of a blank gap.

Real-screen before / after

Deep-link /jetpack-search-demo/?pa_color[]=red on the local docker env, captured with JS blocked at the network layer to freeze the pre-hydration window.

Before (trunk)	After (this PR)

On trunk both filter-wc-attribute wrappers (Color, Size) render with the literal hidden HTML attribute and stay invisible until JS hydration finishes — so the sidebar shows only the Active-filters chip with empty space below. With this PR the wrappers render with the shared skeleton partial: COLOR/SIZE headings plus shimmer rows, and the pre-selected red checkbox seeded from the URL is already visible.

Changes

filter-wc-attribute/render.php

• Replaces the inline $has_buckets read with Search_Blocks::pre_hydration_filter_view() (returns has_buckets, is_initial_loading, show_wrapper)
• Switches wrapper visibility from data-wp-bind--hidden="!state.hasFilterBuckets" to context.wrapperHidden + data-wp-watch="callbacks.syncFilterWrapperVisibility" — the same mechanism used by filter-checkbox / filter-date / filter-wc-rating
• Includes filter-skeleton-partial.php when is_initial_loading is true
• Preserves the existing $all_selected_on_paint logic (guards "All filters applied" state), now short-circuited behind $view['has_buckets']

The SCSS was already complete — style.scss had @include skeleton.shimmer and @include skeleton.filter-rows.

Filter_Wc_Attribute_Render_Test.php (new)

Six render-integration tests including the primary regression guard:

// ?pa_color[]=red triggers is_initial_loading() → true
$markup = $this->render_with_skeleton( array( 'attributeTaxonomy' => 'pa_color' ) );
$this->assertStringContainsString( 'jetpack-search-filter__list--skeleton', $markup );
// Wrapper must be visible while skeleton is up — strict regex so
// `data-wp-bind--hidden` / `wrapperHidden` substrings can't false-positive.
$this->assertSame( 0, preg_match( '/<div[^>]*\s+hidden(?=\s|\/|>|=)/', $markup ) );

Test plan

• composer phpunit in projects/packages/search/ — 354 tests, 772 assertions, all green
• pnpm test-scripts in projects/packages/search/ — 540 tests across 47 suites, all green
• PHPCS clean on all modified files
• Browser sanity check on the local docker env (?pa_color[]=red deep-link) shows the shimmer rows in the attribute filter wrapper

Fixes RSM-2809.

[github-actions]

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[github-actions]

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[jp-launch-control]

Code Coverage Summary

Coverage changed in 3 files.

File	Coverage	Δ%	Δ Uncovered
projects/packages/search/src/search-blocks/blocks/filter-skeleton-partial.php	13/13 (100.00%)	100.00%	-13 💚
projects/packages/search/src/search-blocks/class-search-blocks.php	291/423 (68.79%)	4.49%	-19 💚
projects/packages/search/src/search-blocks/blocks/filter-wc-attribute/render.php	67/81 (82.72%)	82.72%	-62 💚

Full summary · PHP report · JS report

[kangzj]

@claude review plz

[kangzj]

🤖 Review-cycle summary (narrowing iteration) — 402bcd5a8f6 → 3c6be026c9b

2 rounds on the narrowed scope; CI green (25/25 required checks pass, 6 skipping); claude[bot] and copilot-swe-agent both signed off after their flagged items were addressed.

What changed during this loop iteration

Commits added:

• 402bcd5a8f6 — Search Blocks: narrow pre-hydration skeleton to filter-wc-attribute (the user-directed scope change)
• 775420ef708 — Fix stale comments after narrowing skeleton scope (pushed by copilot-swe-agent[bot] during its re-review: store/index.js:1069 JSDoc + filter-wc-attribute/view.js docstring)
• 3c6be026c9b — Address review: update test docblock to reflect attribute-only scope (claude[bot]'s remaining stale-docblock item at Filter_Wc_Attribute_Render_Test.php:184)

Diff summary: 12 files changed, 52 insertions(+), 59 deletions(-).

Reviewers addressed:

Source	Item	Resolution
claude[bot] re-review	store/index.js:1069 stale comment ("for each filter-checkbox block")	Fixed in 775420e (s/filter-checkbox/filter-wc-attribute/)
claude[bot] re-review	Filter_Wc_Attribute_Render_Test.php:184–186 stale docblock claiming parity with filter-checkbox / filter-date	Fixed in 3c6be02; now spells out filter-wc-attribute as the only block on the wrapperHidden plumbing
claude[bot] re-review	Retained-options visibility trade-off (active selection + zero-bucket aggregation → wrapper hides)	Documented in the PR body as an "Accepted trade-off" — pre-#48505 behavior; filter-date unaffected by definition
copilot-swe-agent re-review	Audit of syncFilterWrapperVisibility / wrapperHidden isolation across the JS store	Confirmed safe (context is scoped per block instance by the Interactivity API); also caught and fixed the view.js docstring in 775420e

Unaddressed (flagged for owner): None.

CI: all 25 required checks pass on 3c6be026c9b.

[kangzj]

Course-correction from Jasper: the narrowing direction (commit 402bcd5 + follow-ups) was a misread of the original instruction. filter-wc-attribute needs the loading skeleton just like the other bucket-driven filter blocks — the original PR's intent — and filter-checkbox / filter-date / filter-wc-rating were already working as expected, so they should not have been touched.

Reverted in 63cf38c (Revert narrowing: keep skeleton SSR on all bucket-driven filter blocks). The PR is back to its original goal of bringing filter-wc-attribute to parity with the existing skeleton plumbing.

PR title + body restored. All 354 PHP tests + 540 JS tests pass locally; PHPCS clean.