Get block names directly from the registry (#44658)

This skips the caching that happens in get_blocks_metadata when
core/template-part needs to construct a WP_Theme_JSON to get the template
parts which don't rely on the blocks metadata.

lib/compat/wordpress-6.1/class-wp-theme-json-6-1.php

@@ -131,6 +131,43 @@ class WP_Theme_JSON_6_1 extends WP_Theme_JSON_6_0 {
 		'typography'           => 'typography',
 	);
 
+	/**
+	 * Constructor.
+	 *
+	 * @since 5.8.0
+	 *
+	 * @param array  $theme_json A structure that follows the theme.json schema.
+	 * @param string $origin     Optional. What source of data this object represents.
+	 *                           One of 'default', 'theme', or 'custom'. Default 'theme'.
+	 */
+	public function __construct( $theme_json = array(), $origin = 'theme' ) {
+		if ( ! in_array( $origin, static::VALID_ORIGINS, true ) ) {
+			$origin = 'theme';
+		}
+
+		$this->theme_json    = WP_Theme_JSON_Schema::migrate( $theme_json );
+		$registry            = WP_Block_Type_Registry::get_instance();
+		$valid_block_names   = array_keys( $registry->get_all_registered() );
+		$valid_element_names = array_keys( static::ELEMENTS );
+		$theme_json          = static::sanitize( $this->theme_json, $valid_block_names, $valid_element_names );
+		$this->theme_json    = static::maybe_opt_in_into_settings( $theme_json );
+
+		// Internally, presets are keyed by origin.
+		$nodes = static::get_setting_nodes( $this->theme_json );
+		foreach ( $nodes as $node ) {
+			foreach ( static::PRESETS_METADATA as $preset_metadata ) {
+				$path   = array_merge( $node['path'], $preset_metadata['path'] );
+				$preset = _wp_array_get( $this->theme_json, $path, null );
+				if ( null !== $preset ) {
+					// If the preset is not already keyed by origin.
+					if ( isset( $preset[0] ) || empty( $preset ) ) {
+						_wp_array_set( $this->theme_json, $path, array( $origin => $preset ) );
+					}
+				}
+			}
+		}
+	}
+
 	/**
 	 * Given an element name, returns a class name.
 	 *