432 lines
12 KiB
PHP
432 lines
12 KiB
PHP
<?php
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/**
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* HTML API: WP_HTML_Open_Elements class
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*
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* @package WordPress
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* @subpackage HTML-API
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* @since 6.4.0
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*/
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/**
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* Core class used by the HTML processor during HTML parsing
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* for managing the stack of open elements.
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*
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* This class is designed for internal use by the HTML processor.
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*
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* > Initially, the stack of open elements is empty. The stack grows
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* > downwards; the topmost node on the stack is the first one added
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* > to the stack, and the bottommost node of the stack is the most
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* > recently added node in the stack (notwithstanding when the stack
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* > is manipulated in a random access fashion as part of the handling
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* > for misnested tags).
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*
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* @since 6.4.0
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*
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* @access private
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*
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* @see https://html.spec.whatwg.org/#stack-of-open-elements
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* @see WP_HTML_Processor
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*/
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class WP_HTML_Open_Elements {
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/**
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* Holds the stack of open element references.
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*
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* @since 6.4.0
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*
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* @var WP_HTML_Token[]
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*/
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public $stack = array();
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/**
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* Whether a P element is in button scope currently.
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*
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* This class optimizes scope lookup by pre-calculating
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* this value when elements are added and removed to the
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* stack of open elements which might change its value.
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* This avoids frequent iteration over the stack.
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*
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* @since 6.4.0
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*
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* @var bool
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*/
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private $has_p_in_button_scope = false;
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/**
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* Reports if a specific node is in the stack of open elements.
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*
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* @since 6.4.0
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*
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* @param WP_HTML_Token $token Look for this node in the stack.
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* @return bool Whether the referenced node is in the stack of open elements.
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*/
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public function contains_node( $token ) {
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foreach ( $this->walk_up() as $item ) {
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if ( $token->bookmark_name === $item->bookmark_name ) {
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return true;
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}
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}
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return false;
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}
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/**
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* Returns how many nodes are currently in the stack of open elements.
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*
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* @since 6.4.0
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*
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* @return int How many node are in the stack of open elements.
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*/
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public function count() {
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return count( $this->stack );
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}
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/**
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* Returns the node at the end of the stack of open elements,
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* if one exists. If the stack is empty, returns null.
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*
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* @since 6.4.0
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*
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* @return WP_HTML_Token|null Last node in the stack of open elements, if one exists, otherwise null.
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*/
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public function current_node() {
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$current_node = end( $this->stack );
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return $current_node ? $current_node : null;
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}
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/**
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* Returns whether an element is in a specific scope.
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*
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* ## HTML Support
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*
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* This function skips checking for the termination list because there
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* are no supported elements which appear in the termination list.
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*
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* @since 6.4.0
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*
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* @see https://html.spec.whatwg.org/#has-an-element-in-the-specific-scope
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*
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* @param string $tag_name Name of tag check.
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* @param string[] $termination_list List of elements that terminate the search.
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* @return bool Whether the element was found in a specific scope.
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*/
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public function has_element_in_specific_scope( $tag_name, $termination_list ) {
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foreach ( $this->walk_up() as $node ) {
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if ( $node->node_name === $tag_name ) {
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return true;
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}
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switch ( $node->node_name ) {
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case 'HTML':
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return false;
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}
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if ( in_array( $node->node_name, $termination_list, true ) ) {
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return true;
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}
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}
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return false;
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}
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/**
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* Returns whether a particular element is in scope.
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*
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* @since 6.4.0
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*
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* @see https://html.spec.whatwg.org/#has-an-element-in-scope
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*
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* @param string $tag_name Name of tag to check.
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* @return bool Whether given element is in scope.
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*/
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public function has_element_in_scope( $tag_name ) {
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return $this->has_element_in_specific_scope(
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$tag_name,
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array(
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/*
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* Because it's not currently possible to encounter
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* one of the termination elements, they don't need
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* to be listed here. If they were, they would be
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* unreachable and only waste CPU cycles while
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* scanning through HTML.
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*/
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)
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);
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}
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/**
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* Returns whether a particular element is in list item scope.
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*
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* @since 6.4.0
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*
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* @see https://html.spec.whatwg.org/#has-an-element-in-list-item-scope
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*
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* @throws WP_HTML_Unsupported_Exception Always until this function is implemented.
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*
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* @param string $tag_name Name of tag to check.
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* @return bool Whether given element is in scope.
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*/
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public function has_element_in_list_item_scope( $tag_name ) {
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throw new WP_HTML_Unsupported_Exception( 'Cannot process elements depending on list item scope.' );
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return false; // The linter requires this unreachable code until the function is implemented and can return.
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}
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/**
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* Returns whether a particular element is in button scope.
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*
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* @since 6.4.0
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*
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* @see https://html.spec.whatwg.org/#has-an-element-in-button-scope
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*
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* @param string $tag_name Name of tag to check.
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* @return bool Whether given element is in scope.
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*/
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public function has_element_in_button_scope( $tag_name ) {
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return $this->has_element_in_specific_scope( $tag_name, array( 'BUTTON' ) );
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}
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/**
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* Returns whether a particular element is in table scope.
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*
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* @since 6.4.0
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*
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* @see https://html.spec.whatwg.org/#has-an-element-in-table-scope
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*
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* @throws WP_HTML_Unsupported_Exception Always until this function is implemented.
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*
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* @param string $tag_name Name of tag to check.
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* @return bool Whether given element is in scope.
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*/
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public function has_element_in_table_scope( $tag_name ) {
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throw new WP_HTML_Unsupported_Exception( 'Cannot process elements depending on table scope.' );
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return false; // The linter requires this unreachable code until the function is implemented and can return.
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}
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/**
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* Returns whether a particular element is in select scope.
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*
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* @since 6.4.0
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*
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* @see https://html.spec.whatwg.org/#has-an-element-in-select-scope
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*
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* @throws WP_HTML_Unsupported_Exception Always until this function is implemented.
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*
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* @param string $tag_name Name of tag to check.
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* @return bool Whether given element is in scope.
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*/
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public function has_element_in_select_scope( $tag_name ) {
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throw new WP_HTML_Unsupported_Exception( 'Cannot process elements depending on select scope.' );
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return false; // The linter requires this unreachable code until the function is implemented and can return.
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}
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/**
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* Returns whether a P is in BUTTON scope.
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*
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* @since 6.4.0
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*
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* @see https://html.spec.whatwg.org/#has-an-element-in-button-scope
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*
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* @return bool Whether a P is in BUTTON scope.
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*/
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public function has_p_in_button_scope() {
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return $this->has_p_in_button_scope;
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}
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/**
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* Pops a node off of the stack of open elements.
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*
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* @since 6.4.0
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*
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* @see https://html.spec.whatwg.org/#stack-of-open-elements
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*
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* @return bool Whether a node was popped off of the stack.
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*/
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public function pop() {
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$item = array_pop( $this->stack );
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if ( null === $item ) {
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return false;
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}
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$this->after_element_pop( $item );
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return true;
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}
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/**
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* Pops nodes off of the stack of open elements until one with the given tag name has been popped.
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*
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* @since 6.4.0
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*
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* @see WP_HTML_Open_Elements::pop
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*
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* @param string $tag_name Name of tag that needs to be popped off of the stack of open elements.
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* @return bool Whether a tag of the given name was found and popped off of the stack of open elements.
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*/
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public function pop_until( $tag_name ) {
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foreach ( $this->walk_up() as $item ) {
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$this->pop();
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if ( $tag_name === $item->node_name ) {
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return true;
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}
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}
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return false;
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}
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/**
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* Pushes a node onto the stack of open elements.
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*
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* @since 6.4.0
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*
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* @see https://html.spec.whatwg.org/#stack-of-open-elements
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*
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* @param WP_HTML_Token $stack_item Item to add onto stack.
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*/
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public function push( $stack_item ) {
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$this->stack[] = $stack_item;
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$this->after_element_push( $stack_item );
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}
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/**
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* Removes a specific node from the stack of open elements.
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*
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* @since 6.4.0
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*
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* @param WP_HTML_Token $token The node to remove from the stack of open elements.
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* @return bool Whether the node was found and removed from the stack of open elements.
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*/
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public function remove_node( $token ) {
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foreach ( $this->walk_up() as $position_from_end => $item ) {
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if ( $token->bookmark_name !== $item->bookmark_name ) {
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continue;
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}
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$position_from_start = $this->count() - $position_from_end - 1;
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array_splice( $this->stack, $position_from_start, 1 );
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$this->after_element_pop( $item );
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return true;
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}
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return false;
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}
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/**
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* Steps through the stack of open elements, starting with the top element
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* (added first) and walking downwards to the one added last.
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*
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* This generator function is designed to be used inside a "foreach" loop.
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*
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* Example:
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*
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* $html = '<em><strong><a>We are here';
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* foreach ( $stack->walk_down() as $node ) {
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* echo "{$node->node_name} -> ";
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* }
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* > EM -> STRONG -> A ->
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*
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* To start with the most-recently added element and walk towards the top,
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* see WP_HTML_Open_Elements::walk_up().
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*
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* @since 6.4.0
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*/
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public function walk_down() {
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$count = count( $this->stack );
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for ( $i = 0; $i < $count; $i++ ) {
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yield $this->stack[ $i ];
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}
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}
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/**
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* Steps through the stack of open elements, starting with the bottom element
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* (added last) and walking upwards to the one added first.
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*
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* This generator function is designed to be used inside a "foreach" loop.
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*
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* Example:
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*
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* $html = '<em><strong><a>We are here';
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* foreach ( $stack->walk_up() as $node ) {
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* echo "{$node->node_name} -> ";
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* }
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* > A -> STRONG -> EM ->
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*
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* To start with the first added element and walk towards the bottom,
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* see WP_HTML_Open_Elements::walk_down().
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*
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* @since 6.4.0
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*/
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public function walk_up() {
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for ( $i = count( $this->stack ) - 1; $i >= 0; $i-- ) {
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yield $this->stack[ $i ];
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}
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}
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/*
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* Internal helpers.
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*/
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/**
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* Updates internal flags after adding an element.
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*
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* Certain conditions (such as "has_p_in_button_scope") are maintained here as
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* flags that are only modified when adding and removing elements. This allows
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* the HTML Processor to quickly check for these conditions instead of iterating
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* over the open stack elements upon each new tag it encounters. These flags,
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* however, need to be maintained as items are added and removed from the stack.
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*
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* @since 6.4.0
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*
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* @param WP_HTML_Token $item Element that was added to the stack of open elements.
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*/
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public function after_element_push( $item ) {
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/*
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* When adding support for new elements, expand this switch to trap
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* cases where the precalculated value needs to change.
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*/
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switch ( $item->node_name ) {
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case 'BUTTON':
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$this->has_p_in_button_scope = false;
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break;
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case 'P':
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$this->has_p_in_button_scope = true;
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break;
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}
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}
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/**
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* Updates internal flags after removing an element.
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*
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* Certain conditions (such as "has_p_in_button_scope") are maintained here as
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* flags that are only modified when adding and removing elements. This allows
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* the HTML Processor to quickly check for these conditions instead of iterating
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* over the open stack elements upon each new tag it encounters. These flags,
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* however, need to be maintained as items are added and removed from the stack.
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*
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* @since 6.4.0
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*
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* @param WP_HTML_Token $item Element that was removed from the stack of open elements.
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*/
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public function after_element_pop( $item ) {
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/*
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* When adding support for new elements, expand this switch to trap
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* cases where the precalculated value needs to change.
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*/
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switch ( $item->node_name ) {
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case 'BUTTON':
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$this->has_p_in_button_scope = $this->has_element_in_button_scope( 'P' );
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break;
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case 'P':
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$this->has_p_in_button_scope = $this->has_element_in_button_scope( 'P' );
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break;
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}
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}
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}
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