Search 3.0: add compact search block template

[adamwoodnz]

Fixes #

Proposed changes

• Register a second Jetpack Search block template, "Jetpack Search Results (Compact)", that mirrors the Compact Search pattern (toolbar layout: search input + filter popover + sort popover over a layout="compact" results list).
• Surface the new template alongside the existing sidebar template in the Site Editor's Templates list (Appearance → Editor → Templates → Add New) so site owners can opt into the compact layout without editing the default template or hand-building the pattern.
• Refactor Search_Blocks::get_search_template_content() to take a slug argument (memoized per slug) so register_search_template() can register both templates from one code path.

The compact slug is intentionally not prepended to search_template_hierarchy — only one plugin template should win the /?s=… lookup, and the layout-rich sidebar template (jetpack-search) remains the default. Site owners who want the compact layout to take over /?s=… can either edit the resolved search template in the Site Editor or assign the compact template to a page.

Related product discussion/links

• Linear issue: RSM-1944 — Add search template with compact search

Does this pull request change what data or activity we track or use?

No.

Testing instructions

1. Build the search package (or run a Jetpack site that loads it) with jetpack_search_blocks_enabled true and the search-blocks bundle registered.
2. In Appearance → Editor → Templates, click Add New Template.
3. Confirm both Jetpack Search Results and Jetpack Search Results (Compact) appear in the list of plugin-registered templates.
4. Add the Jetpack Search Results (Compact) template to a page (or open it in the Site Editor) and confirm the rendered layout matches the Compact Search block pattern: a single-row toolbar (search input + filter popover + sort popover) over a compact result list, no sidebar column.
5. Visit /?s=test and confirm the default sidebar layout still resolves (i.e. the compact template did not take over the search hierarchy).
6. Run the package PHP tests:

   jp test php packages/search

   All Search_Blocks_Test cases (including the two new ones — test_register_search_template_registers_compact_variant and the updated empty-content / hierarchy assertions) should pass.

Test results

PHPUnit 12.5.23 by Sebastian Bergmann and contributors.

Runtime:       PHP 8.4.18
Configuration: /workspace/projects/packages/search/phpunit.11.xml.dist

...............................................................  63 / 229 ( 27%)
............................................................... 126 / 229 ( 55%)
............................................................... 189 / 229 ( 82%)
........................................                        229 / 229 (100%)

Time: 00:00.268, Memory: 62.50 MB

OK (229 tests, 406 assertions)

Linear Issue: RSM-1944

  

[github-actions]

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• To test on WoA, go to the Plugins menu on a WoA dev site. Click on the "Upload" button and follow the upgrade flow to be able to upload, install, and activate the Jetpack Beta plugin. Once the plugin is active, go to Jetpack > Jetpack Beta, select your plugin (Jetpack), and enable the cursor/add-compact-search-template-403f branch.
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bin/jetpack-downloader test jetpack cursor/add-compact-search-template-403f

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[github-actions]

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Code Coverage Summary

Coverage changed in 1 file.

File	Coverage	Δ%	Δ Uncovered
projects/packages/search/src/search-blocks/class-search-blocks.php	216/344 (62.79%)	1.41%	-1 💚

Full summary · PHP report · JS report