Global Styles: Fix registration of theme style variation defined block styles

[aaronrobertshaw]

Addresses WordPress/wordpress-develop#6756 (comment)

What?

Ensures theme style variation defined block style variations are supported when saving global styles via the the REST API.

Why?

If block style variations aren't registered they are stripping out during the sanitization of theme json data. This makes it appear as though global style customizations have been lost until the editor is reloaded.

How?

When a theme style variation is selected, its values are copied into the user origin data to be saved. This includes the shared block style variation definitions that need registering.

The REST API has been updated to register shared block style variations prior to saving the global styles. This maintains the data for variations they weren't able to be registered via the normal init filter.

Testing Instructions

1. Register style variations the styles/ember.json (theme style variation) file, paste the following under styles.blocks.variations:

"VariationDark": {
    "blockTypes": [
        "core/group",
        "core/columns"
    ],
    "color": {
            "background": "yellow"
    }
}

2. Open the site editor, go to Styles, apply the "Ember" theme style variation AND DO NOT SAVE IT YET.
3. Go to the site editor, select a group block, and verify the VariationDark is available:
4. Update the VariationDark variation by going to "Global Styles > Blocks > Group > VariationDark". Modify the background color to something else.
5. Save the post. The expected result is that the new background stays as it is and it's not reset.
6. Confirm the global styles API unit tests pass:
   npm run test:unit:php:base -- --filter WP_REST_Global_Styles_Controller_Gutenberg_Test::test_update_item_with_custom_block_style_variations

Screenshots or screencast

Before	After
Screen.Recording.2024-06-12.at.12.26.30.PM.mp4	Screen.Recording.2024-06-12.at.12.25.44.PM.mp4

[github-actions]

This pull request has changed or added PHP files. Please confirm whether these changes need to be synced to WordPress Core, and therefore featured in the next release of WordPress.

If so, it is recommended to create a new Trac ticket and submit a pull request to the WordPress Core Github repository soon after this pull request is merged.

If you're unsure, you can always ask for help in the #core-editor channel in WordPress Slack.

Thank you! ❤️

View changed files

❔ lib/class-wp-rest-global-styles-controller-gutenberg.php
❔ phpunit/class-wp-rest-global-styles-controller-gutenberg-test.php

[github-actions]

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Co-authored-by: aaronrobertshaw <aaronrobertshaw@git.wordpress.org>
Co-authored-by: oandregal <oandregal@git.wordpress.org>

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[aaronrobertshaw]

This will be included in the existing backport: WordPress/wordpress-develop#6756.