Fix block style variation custom CSS output on the front end

[tellthemachines]

Trac ticket: https://core.trac.wordpress.org/ticket/61425

Syncs the changes from WordPress/gutenberg#62526 to core.

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[github-actions]

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[aaronrobertshaw]

While testing, I ran into an issue where custom CSS for a variation's inner block types isn't working on this branch. It works with Gutenberg trunk active.

Theme.json snippet added two TT4

{
	"styles": {
		"blocks": {
			"variations": {
				"Custom": {
					"blockTypes": [
						"core/group"
					],
					"color": {
						"background": "skyblue"
					},
					"spacing": {
						"padding": {
							"top": "1em",
							"right": "1em",
							"bottom": "1em",
							"left": "1em"
						}
					},
					"blocks": {
						"core/group": {
							"color": {
								"background": "aliceblue"
							},
							"spacing": {
								"padding": {
									"top": "1.5em",
									"right": "0.5em",
									"bottom": "1.5em",
									"left": "0.5em"
								}
							},
							"css": "outline: 3px dashed red;"
						}
					}
				}
			},
			"core/button": {
				"variations": {
					"outline": {
						"spacing": {
							"padding": {
								"bottom": "calc(0.6rem - 1px)",
								"left": "calc(1rem - 1px)",
								"right": "calc(1rem - 1px)",
								"top": "calc(0.6rem - 1px)"
							}
						},
						"border": {
							"width": "1px"
						},
						"css": "outline: 3px dashed ivory;"
					}
				}
			},
}

This Branch	With Gutenberg Active

Note on this branch alone, the custom css adding the red outline to inner Group blocks with the "Custom" block style variation is not getting applied.

Quickly dumping out some data and styles at different points, I could see the same variations data being given to the theme.json class in both Core and Gutenberg however the resulting CSS stylesheet for core omits the custom css for the variation's inner blocks.

I haven't had much success putting my finger on the cause just yet and need to switch onto some other tasks that need to make WP6.6 beta3. I'll try and help dig deeper tomorrow.

Some unit tests might also help debug and prevent some future regressions. What do you think?

P.S. We should also add a @since 6.6.0 note to get_styles_for_block flagging it as the release custom css for variations was added or "fixed".

[aaronrobertshaw]

Is it possible that Gutenberg is working due to the changes associated with WordPress/gutenberg#62357?

[tellthemachines]

Thanks for spotting that @aaronrobertshaw! I've fixed the issue now. It was due to one of the changes in Gutenberg, but I've managed to safely add part of that code here without affecting output for other custom CSS.

[tellthemachines]

Because in core we're not setting the css property in get_block_nodes, this will only be true for nested block style variations.

[aaronrobertshaw]

Thanks for the quick turnaround on that fix @tellthemachines 🚀

I can confirm the custom css for inner block type styles for variations is now getting applied correctly on the frontend.

I think we might aso need to add to the @since 6.6.0 comment for get_styles_for_block so it covers the changes here.

[tellthemachines]

Committed in r58421.