Block Styles: Ensure unique classname generation for variations

[aaronrobertshaw]

Trac ticket: https://core.trac.wordpress.org/ticket/61877

This PR backports the PHP changes from WordPress/gutenberg#64511.

What?

Simplifies block style variation class name generation to ensure unique class.

Why?

Avoids potential for non-unique class names and conflicting styles when exact copies of a block are inserted via a repeated pattern.

Further background and context can be found over on WordPress/gutenberg#64511.

How?

Replace the hashing of block attributes in the block style variation classnames with a call to wp_unique_id.

Testing Instructions

Confirm unique classnames on frontend

1. Create a pattern
2. Add a button with the Outline block styles to the pattern
3. Save the pattern and edit a post
4. Insert the above pattern 3 times in the post
5. Save and view the post on the frontend
6. Inspect a button and search the markup for is-style-outline-. You should find CSS with three styles matching that pattern however they should now all be unique.

Ensure no regressions for block style variations on the frontend

1. Add some custom block style variations to your theme. See #57908 for detailed examples or the snippet below for a quick option.
2. Add suitable content to a page, making sure there is enough that nested applications of block style variations can occur
3. In the site editor, apply the custom block style variations to various content, including in a nested fashion
4. Save and confirm the correct styling on the frontend

Example block style variation theme.json partial (place under `/styles`)

{
	"$schema": "https://schemas.wp.org/trunk/theme.json",
	"version": 3,
	"title": "Section A",
	"slug": "section-a",
	"blockTypes": [ "core/group" ],
	"styles": {
		"color": {
			"background": "slategrey",
			"text": "snow"
		},
		"blocks": {
			"core/group": {
				"color": {
					"background": "darkslategrey",
					"text": "whitesmoke"
				}
			}
		}
	}
}

Screenshots or screencast

Simple unique classnames for exact copies of blocks

Block Style Variations still working

Screen.Recording.2024-08-14.at.9.24.28.PM.mp4

---

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Props aaronrobertshaw, martinkrcho, mukesh27, peterwilsoncc.

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[github-actions]

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Test this pull request with WordPress Playground.

[mukeshpanchal27]

Unit tests going failed. That needs to fix.

1) Tests_Block_Supports_WpCreateBlockStyleVariationInstanceName::test_block_style_variation_instance_name_generation
Unexpected deprecation notice for wp_create_block_style_variation_instance_name.
Function wp_create_block_style_variation_instance_name is deprecated since version 6.7.0! Use wp_unique_id instead.
Failed asserting that an array is empty.

/var/www/tests/phpunit/includes/abstract-testcase.php:643
/var/www/tests/phpunit/includes/abstract-testcase.php:655
/var/www/vendor/yoast/phpunit-polyfills/src/TestCases/TestCasePHPUnitGte8.php:82
phpvfscomposer:///var/www/vendor/phpunit/phpunit/phpunit:97
/var/www/vendor/bin/phpunit:118

[aaronrobertshaw]

Thanks for flagging that @mukeshpanchal27 👍

I wasn't too sure on whether the test should be removed or just flagged as expecting the deprecation. I went with flagging the expected deprecation so it can be removed once the deprecated function is.

[peterwilsoncc]

Relocation sale and a question.

[ramonjd]

✅ Unique ids appear for style variations inside multiple patterns on the frontend
✅ Unique style variations rules are being generated for global styles on the frontend, e.g., :root :where(.wp-block-group.is-style-section-a--17)

[ramonjd]

Committed in r58951 / 0a9dcb4