wp_build_state_selector( string $base_selector, string|null $block_selector, string $state ): string

498function wp_build_state_selector( $base_selector, $block_selector, $state ) {499	if ( ! is_string( $block_selector ) || '' === trim( $block_selector ) ) {500		return $base_selector . $state;501	}502 503	$selectors        = wp_split_selector_list( $block_selector );504	$scoped_selectors = array();505 506	foreach ( $selectors as $selector ) {507		$selector = trim( $selector );508		if ( '' === $selector ) {509			continue;510		}511 512		/*513		 * Replace only the leading block selector part (e.g. class name,514		 * attribute selector, ID, or tag name) with the block instance selector.515		 * Preserve anything after that prefix, including modifier classes on the516		 * same element and combinators without spaces.517		 */518		if ( preg_match( '/^([.#]?[-_a-zA-Z0-9]+|\[[^\]]+\])/', $selector, $matches ) ) {519			$scoped_selectors[] = $base_selector . substr( $selector, strlen( $matches[0] ) ) . $state;520			continue;521		}522 523		$scoped_selectors[] = $base_selector . $state;524	}525 526	return empty( $scoped_selectors )527		? $base_selector . $state528		: implode( ', ', $scoped_selectors );529}