Fix: Block pseudo-state styles incorrectly applied to default state

[MaggieCabrera]

What?

When a block defines a custom feature selector in its block.json (e.g. core/button uses .wp-block-button for writingMode rather than the root .wp-block-button .wp-block-button__link), styles set on a pseudo-state like :hover via theme.json were being output under the default-state selector instead of the pseudo-state selector.

Why?

This bug will become more apparent when there's a UI to change the state of the button block after #75627 lands.

How?

In get_block_nodes, the metadata node for a block pseudo-state was built with the original $feature_selectors (e.g. .wp-block-button) rather than the pseudo-scoped version (e.g. .wp-block-button:hover). The fix builds a $pseudo_feature_selectors array that appends the pseudo-selector to every feature selector string before the node is created.

We have added a test to catch this problem should there be a regression

Testing Instructions

Add writing mode to a button block on hover on theme.json, check the frontend and you will see the CSS generated:

Before:
:root :where(.wp-block-button) { writing-mode: vertical-rl; }

After:
:root :where(.wp-block-button:hover) { writing-mode: vertical-rl; }

The unit tests should all pass too

[github-actions]

Flaky tests detected in e499c7e.
Some tests passed with failed attempts. The failures may not be related to this commit but are still reported for visibility. See the documentation for more information.

🔍 Workflow run URL: https://github.com/WordPress/gutenberg/actions/runs/22949653068
📝 Reported issues:

• [Flaky Test] should allow speaking number of initial results #52831 in /test/e2e/specs/editor/various/autocomplete-and-mentions.spec.js

[github-actions]

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Co-authored-by: MaggieCabrera <[email protected]>
Co-authored-by: mikachan <[email protected]>

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[mikachan]

This is testing well for me:

I've left some other comments but I don't think either are blockers.

[mikachan]

Thanks for the updates! This LGTM 👍