Feat: Navigation Link – Add "Show child categories" toggle for taxonomy Category Links

[priyanshuhaldar007]

What?

Closes https://core.trac.wordpress.org/ticket/64988

Adds a showChildCategories boolean attribute to the core/navigation-link block. When enabled on a Category Link block, child categories of the selected parent are automatically fetched and rendered as a nested submenu/dropdown in the frontend navigation.

Why?

The Navigation block's Category Link currently only links to a single category archive — it has no way to expose child categories as a submenu. This is inconsistent with the Page List block, which supports hierarchical parent–child page structures out of the box. Users with hierarchical taxonomies (blogs, WooCommerce stores, taxonomy-heavy sites) are forced to manually construct submenus or write custom code to replicate behavior that Page List provides natively.

How?

• Added showChildCategories: { type: boolean, default: false } to block.json for core/navigation-link.
• Added a ToggleControl in edit.js (block sidebar inspector) that toggles the new attribute. The control is only shown when the selected link kind is taxonomy.
• Updated the PHP render callback (render_block_core_navigation_link) to call get_terms() with parent set to $attributes['id'] when showChildCategories is true and kind is taxonomy.
• Child terms are rendered as <li> navigation items inside a wp-block-navigation__submenu-container, reusing the same Interactivity API markup pattern (data-wp-* attributes, submenu toggle button) as existing inner-block-based submenus.
• The has-child / wp-block-navigation-submenu classes and submenu icon button are applied when either inner blocks or dynamic child terms are present, ensuring consistent hover/click/focus behaviour.

Testing Instructions

1. Activate the Gutenberg plugin on a local WordPress install.
2. Ensure at least one category exists with one or more child categories (e.g. parent: "News", children: "Sports", "Politics").
3. Open a page or post and insert a Navigation block.
4. Add a Category Link block inside the Navigation block and select the parent category (e.g. "News").
5. In the block sidebar (Inspector Controls), confirm a "Show child categories" toggle is visible.
6. Enable the toggle and save/update the post.
7. View the page on the frontend — the parent category link should now display a dropdown submenu containing its child categories.
8. Confirm hover, click, and keyboard navigation on the submenu work correctly.
9. Disable the toggle, save, and confirm the submenu no longer appears on the frontend.
10. Confirm that a Category Link block pointing to a non-taxonomy link (e.g. a page or custom URL) does not show the toggle.

Testing Instructions for Keyboard

1. Tab to the parent category navigation item.
2. Press Enter or Space to open the submenu.
3. Tab through the child category links and confirm focus moves correctly.
4. Press Escape to close the submenu and confirm focus returns to the parent item.

Implementation Screencast

Screen.Recording.2026-04-26.at.12.20.42.PM.mov

Use of AI Tools

Claude (Anthropic) was used to assist with drafting this PR description, and Gemini was used to assist with debugging.

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