diff -r 7b1b88e27a20 -r 48c4eec2b7e6 wp/wp-includes/global-styles-and-settings.php
--- a/wp/wp-includes/global-styles-and-settings.php	Thu Sep 29 08:06:27 2022 +0200
+++ b/wp/wp-includes/global-styles-and-settings.php	Fri Sep 05 18:40:08 2025 +0200
@@ -6,7 +6,7 @@
  */
 
 /**
- * Function to get the settings resulting of merging core, theme, and user data.
+ * Gets the settings resulting of merging core, theme, and user data.
  *
  * @since 5.9.0
  *
@@ -21,28 +21,79 @@
  *                              Valid values are 'all' (core, theme, and user) or 'base' (core and theme).
  *                              If empty or unknown, 'all' is used.
  * }
- *
- * @return array The settings to retrieve.
+ * @return mixed The settings array or individual setting value to retrieve.
  */
 function wp_get_global_settings( $path = array(), $context = array() ) {
 	if ( ! empty( $context['block_name'] ) ) {
-		$path = array_merge( array( 'blocks', $context['block_name'] ), $path );
+		$new_path = array( 'blocks', $context['block_name'] );
+		foreach ( $path as $subpath ) {
+			$new_path[] = $subpath;
+		}
+		$path = $new_path;
 	}
 
+	/*
+	 * This is the default value when no origin is provided or when it is 'all'.
+	 *
+	 * The $origin is used as part of the cache key. Changes here need to account
+	 * for clearing the cache appropriately.
+	 */
 	$origin = 'custom';
-	if ( isset( $context['origin'] ) && 'base' === $context['origin'] ) {
+	if (
+		! wp_theme_has_theme_json() ||
+		( isset( $context['origin'] ) && 'base' === $context['origin'] )
+	) {
 		$origin = 'theme';
 	}
 
-	$settings = WP_Theme_JSON_Resolver::get_merged_data( $origin )->get_settings();
+	/*
+	 * By using the 'theme_json' group, this data is marked to be non-persistent across requests.
+	 * See `wp_cache_add_non_persistent_groups` in src/wp-includes/load.php and other places.
+	 *
+	 * The rationale for this is to make sure derived data from theme.json
+	 * is always fresh from the potential modifications done via hooks
+	 * that can use dynamic data (modify the stylesheet depending on some option,
+	 * settings depending on user permissions, etc.).
+	 * See some of the existing hooks to modify theme.json behavior:
+	 * https://make.wordpress.org/core/2022/10/10/filters-for-theme-json-data/
+	 *
+	 * A different alternative considered was to invalidate the cache upon certain
+	 * events such as options add/update/delete, user meta, etc.
+	 * It was judged not enough, hence this approach.
+	 * See https://github.com/WordPress/gutenberg/pull/45372
+	 */
+	$cache_group = 'theme_json';
+	$cache_key   = 'wp_get_global_settings_' . $origin;
+
+	/*
+	 * Ignore cache when the development mode is set to 'theme', so it doesn't interfere with the theme
+	 * developer's workflow.
+	 */
+	$can_use_cached = ! wp_is_development_mode( 'theme' );
+
+	$settings = false;
+	if ( $can_use_cached ) {
+		$settings = wp_cache_get( $cache_key, $cache_group );
+	}
+
+	if ( false === $settings ) {
+		$settings = WP_Theme_JSON_Resolver::get_merged_data( $origin )->get_settings();
+		if ( $can_use_cached ) {
+			wp_cache_set( $cache_key, $settings, $cache_group );
+		}
+	}
 
 	return _wp_array_get( $settings, $path, $settings );
 }
 
 /**
- * Function to get the styles resulting of merging core, theme, and user data.
+ * Gets the styles resulting of merging core, theme, and user data.
  *
  * @since 5.9.0
+ * @since 6.3.0 the internal link format "var:preset|color|secondary" is resolved
+ *              to "var(--wp--preset--font-size--small)" so consumers don't have to.
+ * @since 6.3.0 `transforms` is now usable in the `context` parameter. In case [`transforms`]['resolve_variables']
+ *              is defined, variables are resolved to their value in the styles.
  *
  * @param array $path    Path to the specific style to retrieve. Optional.
  *                       If empty, will return all styles.
@@ -54,9 +105,11 @@
  *     @type string $origin     Which origin to take data from.
  *                              Valid values are 'all' (core, theme, and user) or 'base' (core and theme).
  *                              If empty or unknown, 'all' is used.
+ *     @type array $transforms Which transformation(s) to apply.
+ *                              Valid value is array( 'resolve-variables' ).
+ *                              If defined, variables are resolved to their value in the styles.
  * }
- *
- * @return array The styles to retrieve.
+ * @return mixed The styles array or individual style value to retrieve.
  */
 function wp_get_global_styles( $path = array(), $context = array() ) {
 	if ( ! empty( $context['block_name'] ) ) {
@@ -68,60 +121,90 @@
 		$origin = 'theme';
 	}
 
-	$styles = WP_Theme_JSON_Resolver::get_merged_data( $origin )->get_raw_data()['styles'];
+	$resolve_variables = isset( $context['transforms'] )
+	&& is_array( $context['transforms'] )
+	&& in_array( 'resolve-variables', $context['transforms'], true );
 
+	$merged_data = WP_Theme_JSON_Resolver::get_merged_data( $origin );
+	if ( $resolve_variables ) {
+		$merged_data = WP_Theme_JSON::resolve_variables( $merged_data );
+	}
+	$styles = $merged_data->get_raw_data()['styles'];
 	return _wp_array_get( $styles, $path, $styles );
 }
 
+
 /**
  * Returns the stylesheet resulting of merging core, theme, and user data.
  *
  * @since 5.9.0
+ * @since 6.1.0 Added 'base-layout-styles' support.
+ * @since 6.6.0 Resolves relative paths in theme.json styles to theme absolute paths.
  *
- * @param array $types Types of styles to load. Optional.
- *                     It accepts 'variables', 'styles', 'presets' as values.
- *                     If empty, it'll load all for themes with theme.json support
- *                     and only [ 'variables', 'presets' ] for themes without theme.json support.
- *
+ * @param array $types Optional. Types of styles to load.
+ *                     It accepts as values 'variables', 'presets', 'styles', 'base-layout-styles'.
+ *                     If empty, it'll load the following:
+ *                     - for themes without theme.json: 'variables', 'presets', 'base-layout-styles'.
+ *                     - for themes with theme.json: 'variables', 'presets', 'styles'.
  * @return string Stylesheet.
  */
 function wp_get_global_stylesheet( $types = array() ) {
-	// Return cached value if it can be used and exists.
-	// It's cached by theme to make sure that theme switching clears the cache.
-	$can_use_cached = (
-		( empty( $types ) ) &&
-		( ! defined( 'WP_DEBUG' ) || ! WP_DEBUG ) &&
-		( ! defined( 'SCRIPT_DEBUG' ) || ! SCRIPT_DEBUG ) &&
-		( ! defined( 'REST_REQUEST' ) || ! REST_REQUEST ) &&
-		! is_admin()
-	);
-	$transient_name = 'global_styles_' . get_stylesheet();
+	/*
+	 * Ignore cache when the development mode is set to 'theme', so it doesn't interfere with the theme
+	 * developer's workflow.
+	 */
+	$can_use_cached = empty( $types ) && ! wp_is_development_mode( 'theme' );
+
+	/*
+	 * By using the 'theme_json' group, this data is marked to be non-persistent across requests.
+	 * @see `wp_cache_add_non_persistent_groups()`.
+	 *
+	 * The rationale for this is to make sure derived data from theme.json
+	 * is always fresh from the potential modifications done via hooks
+	 * that can use dynamic data (modify the stylesheet depending on some option,
+	 * settings depending on user permissions, etc.).
+	 * See some of the existing hooks to modify theme.json behavior:
+	 * @see https://make.wordpress.org/core/2022/10/10/filters-for-theme-json-data/
+	 *
+	 * A different alternative considered was to invalidate the cache upon certain
+	 * events such as options add/update/delete, user meta, etc.
+	 * It was judged not enough, hence this approach.
+	 * @see https://github.com/WordPress/gutenberg/pull/45372
+	 */
+	$cache_group = 'theme_json';
+	$cache_key   = 'wp_get_global_stylesheet';
 	if ( $can_use_cached ) {
-		$cached = get_transient( $transient_name );
+		$cached = wp_cache_get( $cache_key, $cache_group );
 		if ( $cached ) {
 			return $cached;
 		}
 	}
 
-	$tree = WP_Theme_JSON_Resolver::get_merged_data();
+	$tree                = WP_Theme_JSON_Resolver::resolve_theme_file_uris( WP_Theme_JSON_Resolver::get_merged_data() );
+	$supports_theme_json = wp_theme_has_theme_json();
 
-	$supports_theme_json = WP_Theme_JSON_Resolver::theme_has_support();
 	if ( empty( $types ) && ! $supports_theme_json ) {
-		$types = array( 'variables', 'presets' );
+		$types = array( 'variables', 'presets', 'base-layout-styles' );
 	} elseif ( empty( $types ) ) {
 		$types = array( 'variables', 'styles', 'presets' );
 	}
 
 	/*
-	 * If variables are part of the stylesheet,
-	 * we add them for all origins (default, theme, user).
+	 * If variables are part of the stylesheet, then add them.
 	 * This is so themes without a theme.json still work as before 5.9:
 	 * they can override the default presets.
 	 * See https://core.trac.wordpress.org/ticket/54782
 	 */
 	$styles_variables = '';
 	if ( in_array( 'variables', $types, true ) ) {
-		$styles_variables = $tree->get_stylesheet( array( 'variables' ) );
+		/*
+		 * Only use the default, theme, and custom origins. Why?
+		 * Because styles for `blocks` origin are added at a later phase
+		 * (i.e. in the render cycle). Here, only the ones in use are rendered.
+		 * @see wp_add_global_styles_for_blocks
+		 */
+		$origins          = array( 'default', 'theme', 'custom' );
+		$styles_variables = $tree->get_stylesheet( array( 'variables' ), $origins );
 		$types            = array_diff( $types, array( 'variables' ) );
 	}
 
@@ -133,62 +216,399 @@
 	 */
 	$styles_rest = '';
 	if ( ! empty( $types ) ) {
+		/*
+		 * Only use the default, theme, and custom origins. Why?
+		 * Because styles for `blocks` origin are added at a later phase
+		 * (i.e. in the render cycle). Here, only the ones in use are rendered.
+		 * @see wp_add_global_styles_for_blocks
+		 */
 		$origins = array( 'default', 'theme', 'custom' );
-		if ( ! $supports_theme_json ) {
+		/*
+		 * If the theme doesn't have theme.json but supports both appearance tools and color palette,
+		 * the 'theme' origin should be included so color palette presets are also output.
+		 */
+		if ( ! $supports_theme_json && ( current_theme_supports( 'appearance-tools' ) || current_theme_supports( 'border' ) ) && current_theme_supports( 'editor-color-palette' ) ) {
+			$origins = array( 'default', 'theme' );
+		} elseif ( ! $supports_theme_json ) {
 			$origins = array( 'default' );
 		}
 		$styles_rest = $tree->get_stylesheet( $types, $origins );
 	}
 
 	$stylesheet = $styles_variables . $styles_rest;
+	if ( $can_use_cached ) {
+		wp_cache_set( $cache_key, $stylesheet, $cache_group );
+	}
+
+	return $stylesheet;
+}
+
+/**
+ * Gets the global styles custom CSS from theme.json.
+ *
+ * @since 6.2.0
+ *
+ * @return string The global styles custom CSS.
+ */
+function wp_get_global_styles_custom_css() {
+	if ( ! wp_theme_has_theme_json() ) {
+		return '';
+	}
+	/*
+	 * Ignore cache when the development mode is set to 'theme', so it doesn't interfere with the theme
+	 * developer's workflow.
+	 */
+	$can_use_cached = ! wp_is_development_mode( 'theme' );
+
+	/*
+	 * By using the 'theme_json' group, this data is marked to be non-persistent across requests.
+	 * @see `wp_cache_add_non_persistent_groups()`.
+	 *
+	 * The rationale for this is to make sure derived data from theme.json
+	 * is always fresh from the potential modifications done via hooks
+	 * that can use dynamic data (modify the stylesheet depending on some option,
+	 * settings depending on user permissions, etc.).
+	 * See some of the existing hooks to modify theme.json behavior:
+	 * @see https://make.wordpress.org/core/2022/10/10/filters-for-theme-json-data/
+	 *
+	 * A different alternative considered was to invalidate the cache upon certain
+	 * events such as options add/update/delete, user meta, etc.
+	 * It was judged not enough, hence this approach.
+	 * @see https://github.com/WordPress/gutenberg/pull/45372
+	 */
+	$cache_key   = 'wp_get_global_styles_custom_css';
+	$cache_group = 'theme_json';
+	if ( $can_use_cached ) {
+		$cached = wp_cache_get( $cache_key, $cache_group );
+		if ( $cached ) {
+			return $cached;
+		}
+	}
+
+	$tree       = WP_Theme_JSON_Resolver::get_merged_data();
+	$stylesheet = $tree->get_custom_css();
 
 	if ( $can_use_cached ) {
-		// Cache for a minute.
-		// This cache doesn't need to be any longer, we only want to avoid spikes on high-traffic sites.
-		set_transient( $transient_name, $stylesheet, MINUTE_IN_SECONDS );
+		wp_cache_set( $cache_key, $stylesheet, $cache_group );
 	}
 
 	return $stylesheet;
 }
 
 /**
- * Returns a string containing the SVGs to be referenced as filters (duotone).
+ * Adds global style rules to the inline style for each block.
+ *
+ * @since 6.1.0
  *
- * @since 5.9.1
+ * @global WP_Styles $wp_styles
+ */
+function wp_add_global_styles_for_blocks() {
+	global $wp_styles;
+
+	$tree        = WP_Theme_JSON_Resolver::get_merged_data();
+	$block_nodes = $tree->get_styles_block_nodes();
+	foreach ( $block_nodes as $metadata ) {
+		$block_css = $tree->get_styles_for_block( $metadata );
+
+		if ( ! wp_should_load_separate_core_block_assets() ) {
+			wp_add_inline_style( 'global-styles', $block_css );
+			continue;
+		}
+
+		$stylesheet_handle = 'global-styles';
+
+		/*
+		 * When `wp_should_load_separate_core_block_assets()` is true, block styles are
+		 * enqueued for each block on the page in class WP_Block's render function.
+		 * This means there will be a handle in the styles queue for each of those blocks.
+		 * Block-specific global styles should be attached to the global-styles handle, but
+		 * only for blocks on the page, thus we check if the block's handle is in the queue
+		 * before adding the inline style.
+		 * This conditional loading only applies to core blocks.
+		 */
+		if ( isset( $metadata['name'] ) ) {
+			if ( str_starts_with( $metadata['name'], 'core/' ) ) {
+				$block_name   = str_replace( 'core/', '', $metadata['name'] );
+				$block_handle = 'wp-block-' . $block_name;
+				if ( in_array( $block_handle, $wp_styles->queue, true ) ) {
+					wp_add_inline_style( $stylesheet_handle, $block_css );
+				}
+			} else {
+				wp_add_inline_style( $stylesheet_handle, $block_css );
+			}
+		}
+
+		// The likes of block element styles from theme.json do not have  $metadata['name'] set.
+		if ( ! isset( $metadata['name'] ) && ! empty( $metadata['path'] ) ) {
+			$block_name = wp_get_block_name_from_theme_json_path( $metadata['path'] );
+			if ( $block_name ) {
+				if ( str_starts_with( $block_name, 'core/' ) ) {
+					$block_name   = str_replace( 'core/', '', $block_name );
+					$block_handle = 'wp-block-' . $block_name;
+					if ( in_array( $block_handle, $wp_styles->queue, true ) ) {
+						wp_add_inline_style( $stylesheet_handle, $block_css );
+					}
+				} else {
+					wp_add_inline_style( $stylesheet_handle, $block_css );
+				}
+			}
+		}
+	}
+}
+
+/**
+ * Gets the block name from a given theme.json path.
  *
- * @return string
+ * @since 6.3.0
+ * @access private
+ *
+ * @param array $path An array of keys describing the path to a property in theme.json.
+ * @return string Identified block name, or empty string if none found.
  */
-function wp_get_global_styles_svg_filters() {
-	// Return cached value if it can be used and exists.
-	// It's cached by theme to make sure that theme switching clears the cache.
-	$can_use_cached = (
-		( ! defined( 'WP_DEBUG' ) || ! WP_DEBUG ) &&
-		( ! defined( 'SCRIPT_DEBUG' ) || ! SCRIPT_DEBUG ) &&
-		( ! defined( 'REST_REQUEST' ) || ! REST_REQUEST ) &&
-		! is_admin()
+function wp_get_block_name_from_theme_json_path( $path ) {
+	// Block name is expected to be the third item after 'styles' and 'blocks'.
+	if (
+		count( $path ) >= 3
+		&& 'styles' === $path[0]
+		&& 'blocks' === $path[1]
+		&& str_contains( $path[2], '/' )
+	) {
+		return $path[2];
+	}
+
+	/*
+	 * As fallback and for backward compatibility, allow any core block to be
+	 * at any position.
+	 */
+	$result = array_values(
+		array_filter(
+			$path,
+			static function ( $item ) {
+				if ( str_contains( $item, 'core/' ) ) {
+					return true;
+				}
+				return false;
+			}
+		)
 	);
-	$transient_name = 'global_styles_svg_filters_' . get_stylesheet();
+	if ( isset( $result[0] ) ) {
+		return $result[0];
+	}
+	return '';
+}
+
+/**
+ * Checks whether a theme or its parent has a theme.json file.
+ *
+ * @since 6.2.0
+ *
+ * @return bool Returns true if theme or its parent has a theme.json file, false otherwise.
+ */
+function wp_theme_has_theme_json() {
+	static $theme_has_support = array();
+
+	$stylesheet = get_stylesheet();
+
+	if (
+		isset( $theme_has_support[ $stylesheet ] ) &&
+		/*
+		 * Ignore static cache when the development mode is set to 'theme', to avoid interfering with
+		 * the theme developer's workflow.
+		 */
+		! wp_is_development_mode( 'theme' )
+	) {
+		return $theme_has_support[ $stylesheet ];
+	}
+
+	$stylesheet_directory = get_stylesheet_directory();
+	$template_directory   = get_template_directory();
+
+	// This is the same as get_theme_file_path(), which isn't available in load-styles.php context
+	if ( $stylesheet_directory !== $template_directory && file_exists( $stylesheet_directory . '/theme.json' ) ) {
+		$path = $stylesheet_directory . '/theme.json';
+	} else {
+		$path = $template_directory . '/theme.json';
+	}
+
+	/** This filter is documented in wp-includes/link-template.php */
+	$path = apply_filters( 'theme_file_path', $path, 'theme.json' );
+
+	$theme_has_support[ $stylesheet ] = file_exists( $path );
+
+	return $theme_has_support[ $stylesheet ];
+}
+
+/**
+ * Cleans the caches under the theme_json group.
+ *
+ * @since 6.2.0
+ */
+function wp_clean_theme_json_cache() {
+	wp_cache_delete( 'wp_get_global_stylesheet', 'theme_json' );
+	wp_cache_delete( 'wp_get_global_styles_svg_filters', 'theme_json' );
+	wp_cache_delete( 'wp_get_global_settings_custom', 'theme_json' );
+	wp_cache_delete( 'wp_get_global_settings_theme', 'theme_json' );
+	wp_cache_delete( 'wp_get_global_styles_custom_css', 'theme_json' );
+	wp_cache_delete( 'wp_get_theme_data_template_parts', 'theme_json' );
+	WP_Theme_JSON_Resolver::clean_cached_data();
+}
+
+/**
+ * Returns the current theme's wanted patterns (slugs) to be
+ * registered from Pattern Directory.
+ *
+ * @since 6.3.0
+ *
+ * @return string[]
+ */
+function wp_get_theme_directory_pattern_slugs() {
+	return WP_Theme_JSON_Resolver::get_theme_data( array(), array( 'with_supports' => false ) )->get_patterns();
+}
+
+/**
+ * Returns the metadata for the custom templates defined by the theme via theme.json.
+ *
+ * @since 6.4.0
+ *
+ * @return array Associative array of `$template_name => $template_data` pairs,
+ *               with `$template_data` having "title" and "postTypes" fields.
+ */
+function wp_get_theme_data_custom_templates() {
+	return WP_Theme_JSON_Resolver::get_theme_data( array(), array( 'with_supports' => false ) )->get_custom_templates();
+}
+
+/**
+ * Returns the metadata for the template parts defined by the theme.
+ *
+ * @since 6.4.0
+ *
+ * @return array Associative array of `$part_name => $part_data` pairs,
+ *               with `$part_data` having "title" and "area" fields.
+ */
+function wp_get_theme_data_template_parts() {
+	$cache_group    = 'theme_json';
+	$cache_key      = 'wp_get_theme_data_template_parts';
+	$can_use_cached = ! wp_is_development_mode( 'theme' );
+
+	$metadata = false;
 	if ( $can_use_cached ) {
-		$cached = get_transient( $transient_name );
-		if ( $cached ) {
-			return $cached;
+		$metadata = wp_cache_get( $cache_key, $cache_group );
+		if ( false !== $metadata ) {
+			return $metadata;
 		}
 	}
 
-	$supports_theme_json = WP_Theme_JSON_Resolver::theme_has_support();
+	if ( false === $metadata ) {
+		$metadata = WP_Theme_JSON_Resolver::get_theme_data( array(), array( 'with_supports' => false ) )->get_template_parts();
+		if ( $can_use_cached ) {
+			wp_cache_set( $cache_key, $metadata, $cache_group );
+		}
+	}
+
+	return $metadata;
+}
 
-	$origins = array( 'default', 'theme', 'custom' );
-	if ( ! $supports_theme_json ) {
-		$origins = array( 'default' );
+/**
+ * Determines the CSS selector for the block type and property provided,
+ * returning it if available.
+ *
+ * @since 6.3.0
+ *
+ * @param WP_Block_Type $block_type The block's type.
+ * @param string|array  $target     The desired selector's target, `root` or array path.
+ * @param boolean       $fallback   Whether to fall back to broader selector.
+ *
+ * @return string|null CSS selector or `null` if no selector available.
+ */
+function wp_get_block_css_selector( $block_type, $target = 'root', $fallback = false ) {
+	if ( empty( $target ) ) {
+		return null;
+	}
+
+	$has_selectors = ! empty( $block_type->selectors );
+
+	// Root Selector.
+
+	// Calculated before returning as it can be used as fallback for
+	// feature selectors later on.
+	$root_selector = null;
+
+	if ( $has_selectors && isset( $block_type->selectors['root'] ) ) {
+		// Use the selectors API if available.
+		$root_selector = $block_type->selectors['root'];
+	} elseif ( isset( $block_type->supports['__experimentalSelector'] ) && is_string( $block_type->supports['__experimentalSelector'] ) ) {
+		// Use the old experimental selector supports property if set.
+		$root_selector = $block_type->supports['__experimentalSelector'];
+	} else {
+		// If no root selector found, generate default block class selector.
+		$block_name    = str_replace( '/', '-', str_replace( 'core/', '', $block_type->name ) );
+		$root_selector = ".wp-block-{$block_name}";
+	}
+
+	// Return selector if it's the root target we are looking for.
+	if ( 'root' === $target ) {
+		return $root_selector;
 	}
 
-	$tree = WP_Theme_JSON_Resolver::get_merged_data();
-	$svgs = $tree->get_svg_filters( $origins );
-
-	if ( $can_use_cached ) {
-		// Cache for a minute, same as wp_get_global_stylesheet.
-		set_transient( $transient_name, $svgs, MINUTE_IN_SECONDS );
+	// If target is not `root` we have a feature or subfeature as the target.
+	// If the target is a string convert to an array.
+	if ( is_string( $target ) ) {
+		$target = explode( '.', $target );
 	}
 
-	return $svgs;
+	// Feature Selectors ( May fallback to root selector ).
+	if ( 1 === count( $target ) ) {
+		$fallback_selector = $fallback ? $root_selector : null;
+
+		// Prefer the selectors API if available.
+		if ( $has_selectors ) {
+			// Look for selector under `feature.root`.
+			$path             = array( current( $target ), 'root' );
+			$feature_selector = _wp_array_get( $block_type->selectors, $path, null );
+
+			if ( $feature_selector ) {
+				return $feature_selector;
+			}
+
+			// Check if feature selector is set via shorthand.
+			$feature_selector = _wp_array_get( $block_type->selectors, $target, null );
+
+			return is_string( $feature_selector ) ? $feature_selector : $fallback_selector;
+		}
+
+		// Try getting old experimental supports selector value.
+		$path             = array( current( $target ), '__experimentalSelector' );
+		$feature_selector = _wp_array_get( $block_type->supports, $path, null );
+
+		// Nothing to work with, provide fallback or null.
+		if ( null === $feature_selector ) {
+			return $fallback_selector;
+		}
+
+		// Scope the feature selector by the block's root selector.
+		return WP_Theme_JSON::scope_selector( $root_selector, $feature_selector );
+	}
+
+	// Subfeature selector
+	// This may fallback either to parent feature or root selector.
+	$subfeature_selector = null;
+
+	// Use selectors API if available.
+	if ( $has_selectors ) {
+		$subfeature_selector = _wp_array_get( $block_type->selectors, $target, null );
+	}
+
+	// Only return if we have a subfeature selector.
+	if ( $subfeature_selector ) {
+		return $subfeature_selector;
+	}
+
+	// To this point we don't have a subfeature selector. If a fallback
+	// has been requested, remove subfeature from target path and return
+	// results of a call for the parent feature's selector.
+	if ( $fallback ) {
+		return wp_get_block_css_selector( $block_type, $target[0], $fallback );
+	}
+
+	return null;
 }