Block Style Variations: Reuse block metadata in WP_Theme_JSON::get_valid_block_style_variations() for better performance

[ramonjd]

What?

Backporting theme json performance optimizations from https://github.com/WordPress/wordpress-develop/pull/7586

Props @mukeshpanchal27

Why?

Reduce unnecessary calls to ::get_blocks_metadata().

How?

Passing already-fetched data from ::get_blocks_metadata() to ::get_valid_block_style_variations(()

Testing Instructions

CI tests should pass. Smoke test a theme with style variations in the site editor.

Here's an example from https://github.com/WordPress/gutenberg/pull/57908 that you can add under /styles.

{
    "$schema": "https://schemas.wp.org/trunk/theme.json",
    "version": 2,
    "title": "Variation A",
    "blockTypes": [ "core/group", "core/columns", "core/media-text" ],
    "styles": {
        "color": {
            "background": "#eed8d3",
            "text": "#201819"
        },
        "elements": {
            "heading": {
                "color": {
                    "text": "#201819"
                }
            }
        },
        "blocks": {
            "core/group": {
                "color": {
                    "background": "#825f58",
                    "text": "#eed8d3"
                },
                "elements": {
                    "heading": {
                        "color": {
                            "text": "#eed8d3"
                        }
                    }
                }
            }
        }
    }
}

[github-actions[bot]]

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• Labels found: [Type] Performance, Backport from WordPress Core, [Feature] Block Style Variations, No Core Sync Required.

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[github-actions[bot]]

Warning: Type of PR label mismatch

To merge this PR, it requires exactly 1 label indicating the type of PR. Other labels are optional and not being checked here.

• Type-related labels to choose from: [Type] Automated Testing, [Type] Breaking Change, [Type] Bug, [Type] Build Tooling, [Type] Code Quality, [Type] Copy, [Type] Developer Documentation, [Type] Enhancement, [Type] Experimental, [Type] Feature, [Type] New API, [Type] Task, [Type] Technical Prototype, [Type] Performance, [Type] Project Management, [Type] Regression, [Type] Security, [Type] WP Core Ticket, Backport from WordPress Core, Gutenberg Plugin.
• Labels found: [Type] Performance, Backport from WordPress Core, No Core Sync Required.

Read more about Type labels in Gutenberg. Don't worry if you don't have the required permissions to add labels; the PR reviewer should be able to help with the task.

[github-actions[bot]]

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If you're merging code through a pull request on GitHub, copy and paste the following into the bottom of the merge commit message.

Co-authored-by: ramonjd <ramonopoly@git.wordpress.org>
Co-authored-by: mukeshpanchal27 <mukesh27@git.wordpress.org>
Co-authored-by: aaronrobertshaw <aaronrobertshaw@git.wordpress.org>

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[ramonjd]

Thanks for the help and reviews, everyone!