Block Themes: Avoid specificity bump for top-level element-only selec…

…tors

Prevent issues (e.g. links being underlined) caused by a bump in CSS
specificity for top-level element-only global element styles.

Backports the PHP changes from WordPress/gutenberg#63403.

Fixes #61630.
Fixes #61660.
Props aaronrobertshaw, andrewserong, noisysocks.

Built from https://develop.svn.wordpress.org/trunk@58749


git-svn-id: http://core.svn.wordpress.org/trunk@58151 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/class-wp-theme-json.php

@@ -2888,8 +2888,23 @@ static function ( $pseudo_selector ) use ( $selector ) {
 			$declarations = static::update_separator_declarations( $declarations );
 		}
 
+		/*
+		 * Top-level element styles using element-only specificity selectors should
+		 * not get wrapped in `:root :where()` to maintain backwards compatibility.
+		 *
+		 * Pseudo classes, e.g. :hover, :focus etc., are a class-level selector so
+		 * still need to be wrapped in `:root :where` to cap specificity for nested
+		 * variations etc. Pseudo selectors won't match the ELEMENTS selector exactly.
+		 */
+		$element_only_selector = $current_element &&
+			isset( static::ELEMENTS[ $current_element ] ) &&
+			// buttons, captions etc. still need `:root :where()` as they are class based selectors.
+			! isset( static::__EXPERIMENTAL_ELEMENT_CLASS_NAMES[ $current_element ] ) &&
+			static::ELEMENTS[ $current_element ] === $selector;
+
 		// 2. Generate and append the rules that use the general selector.
-		$block_rules .= static::to_ruleset( ":root :where($selector)", $declarations );
+		$general_selector = $element_only_selector ? $selector : ":root :where($selector)";
+		$block_rules     .= static::to_ruleset( $general_selector, $declarations );
 
 		// 3. Generate and append the rules that use the duotone selector.
 		if ( isset( $block_metadata['duotone'] ) && ! empty( $declarations_duotone ) ) {

wp-includes/version.php

@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.7-alpha-58748';
+$wp_version = '6.7-alpha-58749';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.