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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-17 07:56:49 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-17 07:56:49 +0000
commita415c29efee45520ae252d2aa28f1083a521cd7b (patch)
treef4ade4b6668ecc0765de7e1424f7c1427ad433ff /wp-includes/html-api/class-wp-html-processor.php
parentInitial commit. (diff)
downloadwordpress-a415c29efee45520ae252d2aa28f1083a521cd7b.tar.xz
wordpress-a415c29efee45520ae252d2aa28f1083a521cd7b.zip
Adding upstream version 6.4.3+dfsg1.upstream/6.4.3+dfsg1
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
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+<?php
+/**
+ * HTML API: WP_HTML_Processor class
+ *
+ * @package WordPress
+ * @subpackage HTML-API
+ * @since 6.4.0
+ */
+
+/**
+ * Core class used to safely parse and modify an HTML document.
+ *
+ * The HTML Processor class properly parses and modifies HTML5 documents.
+ *
+ * It supports a subset of the HTML5 specification, and when it encounters
+ * unsupported markup, it aborts early to avoid unintentionally breaking
+ * the document. The HTML Processor should never break an HTML document.
+ *
+ * While the `WP_HTML_Tag_Processor` is a valuable tool for modifying
+ * attributes on individual HTML tags, the HTML Processor is more capable
+ * and useful for the following operations:
+ *
+ * - Querying based on nested HTML structure.
+ *
+ * Eventually the HTML Processor will also support:
+ * - Wrapping a tag in surrounding HTML.
+ * - Unwrapping a tag by removing its parent.
+ * - Inserting and removing nodes.
+ * - Reading and changing inner content.
+ * - Navigating up or around HTML structure.
+ *
+ * ## Usage
+ *
+ * Use of this class requires three steps:
+ *
+ * 1. Call a static creator method with your input HTML document.
+ * 2. Find the location in the document you are looking for.
+ * 3. Request changes to the document at that location.
+ *
+ * Example:
+ *
+ * $processor = WP_HTML_Processor::create_fragment( $html );
+ * if ( $processor->next_tag( array( 'breadcrumbs' => array( 'DIV', 'FIGURE', 'IMG' ) ) ) ) {
+ * $processor->add_class( 'responsive-image' );
+ * }
+ *
+ * #### Breadcrumbs
+ *
+ * Breadcrumbs represent the stack of open elements from the root
+ * of the document or fragment down to the currently-matched node,
+ * if one is currently selected. Call WP_HTML_Processor::get_breadcrumbs()
+ * to inspect the breadcrumbs for a matched tag.
+ *
+ * Breadcrumbs can specify nested HTML structure and are equivalent
+ * to a CSS selector comprising tag names separated by the child
+ * combinator, such as "DIV > FIGURE > IMG".
+ *
+ * Since all elements find themselves inside a full HTML document
+ * when parsed, the return value from `get_breadcrumbs()` will always
+ * contain any implicit outermost elements. For example, when parsing
+ * with `create_fragment()` in the `BODY` context (the default), any
+ * tag in the given HTML document will contain `array( 'HTML', 'BODY', … )`
+ * in its breadcrumbs.
+ *
+ * Despite containing the implied outermost elements in their breadcrumbs,
+ * tags may be found with the shortest-matching breadcrumb query. That is,
+ * `array( 'IMG' )` matches all IMG elements and `array( 'P', 'IMG' )`
+ * matches all IMG elements directly inside a P element. To ensure that no
+ * partial matches erroneously match it's possible to specify in a query
+ * the full breadcrumb match all the way down from the root HTML element.
+ *
+ * Example:
+ *
+ * $html = '<figure><img><figcaption>A <em>lovely</em> day outside</figcaption></figure>';
+ * // ----- Matches here.
+ * $processor->next_tag( array( 'breadcrumbs' => array( 'FIGURE', 'IMG' ) ) );
+ *
+ * $html = '<figure><img><figcaption>A <em>lovely</em> day outside</figcaption></figure>';
+ * // ---- Matches here.
+ * $processor->next_tag( array( 'breadcrumbs' => array( 'FIGURE', 'FIGCAPTION', 'EM' ) ) );
+ *
+ * $html = '<div><img></div><img>';
+ * // ----- Matches here, because IMG must be a direct child of the implicit BODY.
+ * $processor->next_tag( array( 'breadcrumbs' => array( 'BODY', 'IMG' ) ) );
+ *
+ * ## HTML Support
+ *
+ * This class implements a small part of the HTML5 specification.
+ * It's designed to operate within its support and abort early whenever
+ * encountering circumstances it can't properly handle. This is
+ * the principle way in which this class remains as simple as possible
+ * without cutting corners and breaking compliance.
+ *
+ * ### Supported elements
+ *
+ * If any unsupported element appears in the HTML input the HTML Processor
+ * will abort early and stop all processing. This draconian measure ensures
+ * that the HTML Processor won't break any HTML it doesn't fully understand.
+ *
+ * The following list specifies the HTML tags that _are_ supported:
+ *
+ * - Links: A.
+ * - The formatting elements: B, BIG, CODE, EM, FONT, I, SMALL, STRIKE, STRONG, TT, U.
+ * - Containers: DIV, FIGCAPTION, FIGURE, SPAN.
+ * - Form elements: BUTTON.
+ * - Paragraph: P.
+ * - Void elements: IMG.
+ *
+ * ### Supported markup
+ *
+ * Some kinds of non-normative HTML involve reconstruction of formatting elements and
+ * re-parenting of mis-nested elements. For example, a DIV tag found inside a TABLE
+ * may in fact belong _before_ the table in the DOM. If the HTML Processor encounters
+ * such a case it will stop processing.
+ *
+ * The following list specifies HTML markup that _is_ supported:
+ *
+ * - Markup involving only those tags listed above.
+ * - Fully-balanced and non-overlapping tags.
+ * - HTML with unexpected tag closers.
+ * - Some unbalanced or overlapping tags.
+ * - P tags after unclosed P tags.
+ * - BUTTON tags after unclosed BUTTON tags.
+ * - A tags after unclosed A tags that don't involve any active formatting elements.
+ *
+ * @since 6.4.0
+ *
+ * @see WP_HTML_Tag_Processor
+ * @see https://html.spec.whatwg.org/
+ */
+class WP_HTML_Processor extends WP_HTML_Tag_Processor {
+ /**
+ * The maximum number of bookmarks allowed to exist at any given time.
+ *
+ * HTML processing requires more bookmarks than basic tag processing,
+ * so this class constant from the Tag Processor is overwritten.
+ *
+ * @since 6.4.0
+ *
+ * @var int
+ */
+ const MAX_BOOKMARKS = 100;
+
+ /**
+ * Static query for instructing the Tag Processor to visit every token.
+ *
+ * @access private
+ *
+ * @since 6.4.0
+ *
+ * @var array
+ */
+ const VISIT_EVERYTHING = array( 'tag_closers' => 'visit' );
+
+ /**
+ * Holds the working state of the parser, including the stack of
+ * open elements and the stack of active formatting elements.
+ *
+ * Initialized in the constructor.
+ *
+ * @since 6.4.0
+ *
+ * @var WP_HTML_Processor_State
+ */
+ private $state = null;
+
+ /**
+ * Used to create unique bookmark names.
+ *
+ * This class sets a bookmark for every tag in the HTML document that it encounters.
+ * The bookmark name is auto-generated and increments, starting with `1`. These are
+ * internal bookmarks and are automatically released when the referring WP_HTML_Token
+ * goes out of scope and is garbage-collected.
+ *
+ * @since 6.4.0
+ *
+ * @see WP_HTML_Processor::$release_internal_bookmark_on_destruct
+ *
+ * @var int
+ */
+ private $bookmark_counter = 0;
+
+ /**
+ * Stores an explanation for why something failed, if it did.
+ *
+ * @see self::get_last_error
+ *
+ * @since 6.4.0
+ *
+ * @var string|null
+ */
+ private $last_error = null;
+
+ /**
+ * Releases a bookmark when PHP garbage-collects its wrapping WP_HTML_Token instance.
+ *
+ * This function is created inside the class constructor so that it can be passed to
+ * the stack of open elements and the stack of active formatting elements without
+ * exposing it as a public method on the class.
+ *
+ * @since 6.4.0
+ *
+ * @var closure
+ */
+ private $release_internal_bookmark_on_destruct = null;
+
+ /*
+ * Public Interface Functions
+ */
+
+ /**
+ * Creates an HTML processor in the fragment parsing mode.
+ *
+ * Use this for cases where you are processing chunks of HTML that
+ * will be found within a bigger HTML document, such as rendered
+ * block output that exists within a post, `the_content` inside a
+ * rendered site layout.
+ *
+ * Fragment parsing occurs within a context, which is an HTML element
+ * that the document will eventually be placed in. It becomes important
+ * when special elements have different rules than others, such as inside
+ * a TEXTAREA or a TITLE tag where things that look like tags are text,
+ * or inside a SCRIPT tag where things that look like HTML syntax are JS.
+ *
+ * The context value should be a representation of the tag into which the
+ * HTML is found. For most cases this will be the body element. The HTML
+ * form is provided because a context element may have attributes that
+ * impact the parse, such as with a SCRIPT tag and its `type` attribute.
+ *
+ * ## Current HTML Support
+ *
+ * - The only supported context is `<body>`, which is the default value.
+ * - The only supported document encoding is `UTF-8`, which is the default value.
+ *
+ * @since 6.4.0
+ *
+ * @param string $html Input HTML fragment to process.
+ * @param string $context Context element for the fragment, must be default of `<body>`.
+ * @param string $encoding Text encoding of the document; must be default of 'UTF-8'.
+ * @return WP_HTML_Processor|null The created processor if successful, otherwise null.
+ */
+ public static function create_fragment( $html, $context = '<body>', $encoding = 'UTF-8' ) {
+ if ( '<body>' !== $context || 'UTF-8' !== $encoding ) {
+ return null;
+ }
+
+ $p = new self( $html, self::CONSTRUCTOR_UNLOCK_CODE );
+ $p->state->context_node = array( 'BODY', array() );
+ $p->state->insertion_mode = WP_HTML_Processor_State::INSERTION_MODE_IN_BODY;
+
+ // @TODO: Create "fake" bookmarks for non-existent but implied nodes.
+ $p->bookmarks['root-node'] = new WP_HTML_Span( 0, 0 );
+ $p->bookmarks['context-node'] = new WP_HTML_Span( 0, 0 );
+
+ $p->state->stack_of_open_elements->push(
+ new WP_HTML_Token(
+ 'root-node',
+ 'HTML',
+ false
+ )
+ );
+
+ $p->state->stack_of_open_elements->push(
+ new WP_HTML_Token(
+ 'context-node',
+ $p->state->context_node[0],
+ false
+ )
+ );
+
+ return $p;
+ }
+
+ /**
+ * Constructor.
+ *
+ * Do not use this method. Use the static creator methods instead.
+ *
+ * @access private
+ *
+ * @since 6.4.0
+ *
+ * @see WP_HTML_Processor::create_fragment()
+ *
+ * @param string $html HTML to process.
+ * @param string|null $use_the_static_create_methods_instead This constructor should not be called manually.
+ */
+ public function __construct( $html, $use_the_static_create_methods_instead = null ) {
+ parent::__construct( $html );
+
+ if ( self::CONSTRUCTOR_UNLOCK_CODE !== $use_the_static_create_methods_instead ) {
+ _doing_it_wrong(
+ __METHOD__,
+ sprintf(
+ /* translators: %s: WP_HTML_Processor::create_fragment(). */
+ __( 'Call %s to create an HTML Processor instead of calling the constructor directly.' ),
+ '<code>WP_HTML_Processor::create_fragment()</code>'
+ ),
+ '6.4.0'
+ );
+ }
+
+ $this->state = new WP_HTML_Processor_State();
+
+ /*
+ * Create this wrapper so that it's possible to pass
+ * a private method into WP_HTML_Token classes without
+ * exposing it to any public API.
+ */
+ $this->release_internal_bookmark_on_destruct = function ( $name ) {
+ parent::release_bookmark( $name );
+ };
+ }
+
+ /**
+ * Returns the last error, if any.
+ *
+ * Various situations lead to parsing failure but this class will
+ * return `false` in all those cases. To determine why something
+ * failed it's possible to request the last error. This can be
+ * helpful to know to distinguish whether a given tag couldn't
+ * be found or if content in the document caused the processor
+ * to give up and abort processing.
+ *
+ * Example
+ *
+ * $processor = WP_HTML_Processor::create_fragment( '<template><strong><button><em><p><em>' );
+ * false === $processor->next_tag();
+ * WP_HTML_Processor::ERROR_UNSUPPORTED === $processor->get_last_error();
+ *
+ * @since 6.4.0
+ *
+ * @see self::ERROR_UNSUPPORTED
+ * @see self::ERROR_EXCEEDED_MAX_BOOKMARKS
+ *
+ * @return string|null The last error, if one exists, otherwise null.
+ */
+ public function get_last_error() {
+ return $this->last_error;
+ }
+
+ /**
+ * Finds the next tag matching the $query.
+ *
+ * @TODO: Support matching the class name and tag name.
+ *
+ * @since 6.4.0
+ *
+ * @throws Exception When unable to allocate a bookmark for the next token in the input HTML document.
+ *
+ * @param array|string|null $query {
+ * Optional. Which tag name to find, having which class, etc. Default is to find any tag.
+ *
+ * @type string|null $tag_name Which tag to find, or `null` for "any tag."
+ * @type int|null $match_offset Find the Nth tag matching all search criteria.
+ * 1 for "first" tag, 3 for "third," etc.
+ * Defaults to first tag.
+ * @type string|null $class_name Tag must contain this whole class name to match.
+ * @type string[] $breadcrumbs DOM sub-path at which element is found, e.g. `array( 'FIGURE', 'IMG' )`.
+ * May also contain the wildcard `*` which matches a single element, e.g. `array( 'SECTION', '*' )`.
+ * }
+ * @return bool Whether a tag was matched.
+ */
+ public function next_tag( $query = null ) {
+ if ( null === $query ) {
+ while ( $this->step() ) {
+ if ( ! $this->is_tag_closer() ) {
+ return true;
+ }
+ }
+
+ return false;
+ }
+
+ if ( is_string( $query ) ) {
+ $query = array( 'breadcrumbs' => array( $query ) );
+ }
+
+ if ( ! is_array( $query ) ) {
+ _doing_it_wrong(
+ __METHOD__,
+ __( 'Please pass a query array to this function.' ),
+ '6.4.0'
+ );
+ return false;
+ }
+
+ if ( ! ( array_key_exists( 'breadcrumbs', $query ) && is_array( $query['breadcrumbs'] ) ) ) {
+ while ( $this->step() ) {
+ if ( ! $this->is_tag_closer() ) {
+ return true;
+ }
+ }
+
+ return false;
+ }
+
+ if ( isset( $query['tag_closers'] ) && 'visit' === $query['tag_closers'] ) {
+ _doing_it_wrong(
+ __METHOD__,
+ __( 'Cannot visit tag closers in HTML Processor.' ),
+ '6.4.0'
+ );
+ return false;
+ }
+
+ $breadcrumbs = $query['breadcrumbs'];
+ $match_offset = isset( $query['match_offset'] ) ? (int) $query['match_offset'] : 1;
+
+ while ( $match_offset > 0 && $this->step() ) {
+ if ( $this->matches_breadcrumbs( $breadcrumbs ) && 0 === --$match_offset ) {
+ return true;
+ }
+ }
+
+ return false;
+ }
+
+ /**
+ * Indicates if the currently-matched tag matches the given breadcrumbs.
+ *
+ * A "*" represents a single tag wildcard, where any tag matches, but not no tags.
+ *
+ * At some point this function _may_ support a `**` syntax for matching any number
+ * of unspecified tags in the breadcrumb stack. This has been intentionally left
+ * out, however, to keep this function simple and to avoid introducing backtracking,
+ * which could open up surprising performance breakdowns.
+ *
+ * Example:
+ *
+ * $processor = WP_HTML_Processor::create_fragment( '<div><span><figure><img></figure></span></div>' );
+ * $processor->next_tag( 'img' );
+ * true === $processor->matches_breadcrumbs( array( 'figure', 'img' ) );
+ * true === $processor->matches_breadcrumbs( array( 'span', 'figure', 'img' ) );
+ * false === $processor->matches_breadcrumbs( array( 'span', 'img' ) );
+ * true === $processor->matches_breadcrumbs( array( 'span', '*', 'img' ) );
+ *
+ * @since 6.4.0
+ *
+ * @param string[] $breadcrumbs DOM sub-path at which element is found, e.g. `array( 'FIGURE', 'IMG' )`.
+ * May also contain the wildcard `*` which matches a single element, e.g. `array( 'SECTION', '*' )`.
+ * @return bool Whether the currently-matched tag is found at the given nested structure.
+ */
+ public function matches_breadcrumbs( $breadcrumbs ) {
+ if ( ! $this->get_tag() ) {
+ return false;
+ }
+
+ // Everything matches when there are zero constraints.
+ if ( 0 === count( $breadcrumbs ) ) {
+ return true;
+ }
+
+ // Start at the last crumb.
+ $crumb = end( $breadcrumbs );
+
+ if ( '*' !== $crumb && $this->get_tag() !== strtoupper( $crumb ) ) {
+ return false;
+ }
+
+ foreach ( $this->state->stack_of_open_elements->walk_up() as $node ) {
+ $crumb = strtoupper( current( $breadcrumbs ) );
+
+ if ( '*' !== $crumb && $node->node_name !== $crumb ) {
+ return false;
+ }
+
+ if ( false === prev( $breadcrumbs ) ) {
+ return true;
+ }
+ }
+
+ return false;
+ }
+
+ /**
+ * Steps through the HTML document and stop at the next tag, if any.
+ *
+ * @since 6.4.0
+ *
+ * @throws Exception When unable to allocate a bookmark for the next token in the input HTML document.
+ *
+ * @see self::PROCESS_NEXT_NODE
+ * @see self::REPROCESS_CURRENT_NODE
+ *
+ * @param string $node_to_process Whether to parse the next node or reprocess the current node.
+ * @return bool Whether a tag was matched.
+ */
+ public function step( $node_to_process = self::PROCESS_NEXT_NODE ) {
+ // Refuse to proceed if there was a previous error.
+ if ( null !== $this->last_error ) {
+ return false;
+ }
+
+ if ( self::PROCESS_NEXT_NODE === $node_to_process ) {
+ /*
+ * Void elements still hop onto the stack of open elements even though
+ * there's no corresponding closing tag. This is important for managing
+ * stack-based operations such as "navigate to parent node" or checking
+ * on an element's breadcrumbs.
+ *
+ * When moving on to the next node, therefore, if the bottom-most element
+ * on the stack is a void element, it must be closed.
+ *
+ * @TODO: Once self-closing foreign elements and BGSOUND are supported,
+ * they must also be implicitly closed here too. BGSOUND is
+ * special since it's only self-closing if the self-closing flag
+ * is provided in the opening tag, otherwise it expects a tag closer.
+ */
+ $top_node = $this->state->stack_of_open_elements->current_node();
+ if ( $top_node && self::is_void( $top_node->node_name ) ) {
+ $this->state->stack_of_open_elements->pop();
+ }
+
+ parent::next_tag( self::VISIT_EVERYTHING );
+ }
+
+ // Finish stepping when there are no more tokens in the document.
+ if ( null === $this->get_tag() ) {
+ return false;
+ }
+
+ $this->state->current_token = new WP_HTML_Token(
+ $this->bookmark_tag(),
+ $this->get_tag(),
+ $this->is_tag_closer(),
+ $this->release_internal_bookmark_on_destruct
+ );
+
+ try {
+ switch ( $this->state->insertion_mode ) {
+ case WP_HTML_Processor_State::INSERTION_MODE_IN_BODY:
+ return $this->step_in_body();
+
+ default:
+ $this->last_error = self::ERROR_UNSUPPORTED;
+ throw new WP_HTML_Unsupported_Exception( "No support for parsing in the '{$this->state->insertion_mode}' state." );
+ }
+ } catch ( WP_HTML_Unsupported_Exception $e ) {
+ /*
+ * Exceptions are used in this class to escape deep call stacks that
+ * otherwise might involve messier calling and return conventions.
+ */
+ return false;
+ }
+ }
+
+ /**
+ * Computes the HTML breadcrumbs for the currently-matched node, if matched.
+ *
+ * Breadcrumbs start at the outermost parent and descend toward the matched element.
+ * They always include the entire path from the root HTML node to the matched element.
+ *
+ * @TODO: It could be more efficient to expose a generator-based version of this function
+ * to avoid creating the array copy on tag iteration. If this is done, it would likely
+ * be more useful to walk up the stack when yielding instead of starting at the top.
+ *
+ * Example
+ *
+ * $processor = WP_HTML_Processor::create_fragment( '<p><strong><em><img></em></strong></p>' );
+ * $processor->next_tag( 'IMG' );
+ * $processor->get_breadcrumbs() === array( 'HTML', 'BODY', 'P', 'STRONG', 'EM', 'IMG' );
+ *
+ * @since 6.4.0
+ *
+ * @return string[]|null Array of tag names representing path to matched node, if matched, otherwise NULL.
+ */
+ public function get_breadcrumbs() {
+ if ( ! $this->get_tag() ) {
+ return null;
+ }
+
+ $breadcrumbs = array();
+ foreach ( $this->state->stack_of_open_elements->walk_down() as $stack_item ) {
+ $breadcrumbs[] = $stack_item->node_name;
+ }
+
+ return $breadcrumbs;
+ }
+
+ /**
+ * Parses next element in the 'in body' insertion mode.
+ *
+ * This internal function performs the 'in body' insertion mode
+ * logic for the generalized WP_HTML_Processor::step() function.
+ *
+ * @since 6.4.0
+ *
+ * @throws WP_HTML_Unsupported_Exception When encountering unsupported HTML input.
+ *
+ * @see https://html.spec.whatwg.org/#parsing-main-inbody
+ * @see WP_HTML_Processor::step
+ *
+ * @return bool Whether an element was found.
+ */
+ private function step_in_body() {
+ $tag_name = $this->get_tag();
+ $op_sigil = $this->is_tag_closer() ? '-' : '+';
+ $op = "{$op_sigil}{$tag_name}";
+
+ switch ( $op ) {
+ /*
+ * > A start tag whose tag name is "button"
+ */
+ case '+BUTTON':
+ if ( $this->state->stack_of_open_elements->has_element_in_scope( 'BUTTON' ) ) {
+ // @TODO: Indicate a parse error once it's possible. This error does not impact the logic here.
+ $this->generate_implied_end_tags();
+ $this->state->stack_of_open_elements->pop_until( 'BUTTON' );
+ }
+
+ $this->reconstruct_active_formatting_elements();
+ $this->insert_html_element( $this->state->current_token );
+ $this->state->frameset_ok = false;
+
+ return true;
+
+ /*
+ * > A start tag whose tag name is one of: "address", "article", "aside",
+ * > "blockquote", "center", "details", "dialog", "dir", "div", "dl",
+ * > "fieldset", "figcaption", "figure", "footer", "header", "hgroup",
+ * > "main", "menu", "nav", "ol", "p", "search", "section", "summary", "ul"
+ */
+ case '+BLOCKQUOTE':
+ case '+DIV':
+ case '+FIGCAPTION':
+ case '+FIGURE':
+ case '+P':
+ if ( $this->state->stack_of_open_elements->has_p_in_button_scope() ) {
+ $this->close_a_p_element();
+ }
+
+ $this->insert_html_element( $this->state->current_token );
+ return true;
+
+ /*
+ * > An end tag whose tag name is one of: "address", "article", "aside", "blockquote",
+ * > "button", "center", "details", "dialog", "dir", "div", "dl", "fieldset",
+ * > "figcaption", "figure", "footer", "header", "hgroup", "listing", "main",
+ * > "menu", "nav", "ol", "pre", "search", "section", "summary", "ul"
+ */
+ case '-BLOCKQUOTE':
+ case '-BUTTON':
+ case '-DIV':
+ case '-FIGCAPTION':
+ case '-FIGURE':
+ if ( ! $this->state->stack_of_open_elements->has_element_in_scope( $tag_name ) ) {
+ // @TODO: Report parse error.
+ // Ignore the token.
+ return $this->step();
+ }
+
+ $this->generate_implied_end_tags();
+ if ( $this->state->stack_of_open_elements->current_node()->node_name !== $tag_name ) {
+ // @TODO: Record parse error: this error doesn't impact parsing.
+ }
+ $this->state->stack_of_open_elements->pop_until( $tag_name );
+ return true;
+
+ /*
+ * > An end tag whose tag name is "p"
+ */
+ case '-P':
+ if ( ! $this->state->stack_of_open_elements->has_p_in_button_scope() ) {
+ $this->insert_html_element( $this->state->current_token );
+ }
+
+ $this->close_a_p_element();
+ return true;
+
+ // > A start tag whose tag name is "a"
+ case '+A':
+ foreach ( $this->state->active_formatting_elements->walk_up() as $item ) {
+ switch ( $item->node_name ) {
+ case 'marker':
+ break;
+
+ case 'A':
+ $this->run_adoption_agency_algorithm();
+ $this->state->active_formatting_elements->remove_node( $item );
+ $this->state->stack_of_open_elements->remove_node( $item );
+ break;
+ }
+ }
+
+ $this->reconstruct_active_formatting_elements();
+ $this->insert_html_element( $this->state->current_token );
+ $this->state->active_formatting_elements->push( $this->state->current_token );
+ return true;
+
+ /*
+ * > A start tag whose tag name is one of: "b", "big", "code", "em", "font", "i",
+ * > "s", "small", "strike", "strong", "tt", "u"
+ */
+ case '+B':
+ case '+BIG':
+ case '+CODE':
+ case '+EM':
+ case '+FONT':
+ case '+I':
+ case '+S':
+ case '+SMALL':
+ case '+STRIKE':
+ case '+STRONG':
+ case '+TT':
+ case '+U':
+ $this->reconstruct_active_formatting_elements();
+ $this->insert_html_element( $this->state->current_token );
+ $this->state->active_formatting_elements->push( $this->state->current_token );
+ return true;
+
+ /*
+ * > An end tag whose tag name is one of: "a", "b", "big", "code", "em", "font", "i",
+ * > "nobr", "s", "small", "strike", "strong", "tt", "u"
+ */
+ case '-A':
+ case '-B':
+ case '-BIG':
+ case '-CODE':
+ case '-EM':
+ case '-FONT':
+ case '-I':
+ case '-S':
+ case '-SMALL':
+ case '-STRIKE':
+ case '-STRONG':
+ case '-TT':
+ case '-U':
+ $this->run_adoption_agency_algorithm();
+ return true;
+
+ /*
+ * > A start tag whose tag name is one of: "area", "br", "embed", "img", "keygen", "wbr"
+ */
+ case '+IMG':
+ $this->reconstruct_active_formatting_elements();
+ $this->insert_html_element( $this->state->current_token );
+ return true;
+
+ /*
+ * > Any other start tag
+ */
+ case '+SPAN':
+ $this->reconstruct_active_formatting_elements();
+ $this->insert_html_element( $this->state->current_token );
+ return true;
+
+ /*
+ * Any other end tag
+ */
+ case '-SPAN':
+ foreach ( $this->state->stack_of_open_elements->walk_up() as $item ) {
+ // > If node is an HTML element with the same tag name as the token, then:
+ if ( $item->node_name === $tag_name ) {
+ $this->generate_implied_end_tags( $tag_name );
+
+ // > If node is not the current node, then this is a parse error.
+
+ $this->state->stack_of_open_elements->pop_until( $tag_name );
+ return true;
+ }
+
+ // > Otherwise, if node is in the special category, then this is a parse error; ignore the token, and return.
+ if ( self::is_special( $item->node_name ) ) {
+ return $this->step();
+ }
+ }
+ // Execution should not reach here; if it does then something went wrong.
+ return false;
+
+ default:
+ $this->last_error = self::ERROR_UNSUPPORTED;
+ throw new WP_HTML_Unsupported_Exception( "Cannot process {$tag_name} element." );
+ }
+ }
+
+ /*
+ * Internal helpers
+ */
+
+ /**
+ * Creates a new bookmark for the currently-matched tag and returns the generated name.
+ *
+ * @since 6.4.0
+ *
+ * @throws Exception When unable to allocate requested bookmark.
+ *
+ * @return string|false Name of created bookmark, or false if unable to create.
+ */
+ private function bookmark_tag() {
+ if ( ! $this->get_tag() ) {
+ return false;
+ }
+
+ if ( ! parent::set_bookmark( ++$this->bookmark_counter ) ) {
+ $this->last_error = self::ERROR_EXCEEDED_MAX_BOOKMARKS;
+ throw new Exception( 'could not allocate bookmark' );
+ }
+
+ return "{$this->bookmark_counter}";
+ }
+
+ /*
+ * HTML semantic overrides for Tag Processor
+ */
+
+ /**
+ * Returns the uppercase name of the matched tag.
+ *
+ * The semantic rules for HTML specify that certain tags be reprocessed
+ * with a different tag name. Because of this, the tag name presented
+ * by the HTML Processor may differ from the one reported by the HTML
+ * Tag Processor, which doesn't apply these semantic rules.
+ *
+ * Example:
+ *
+ * $processor = new WP_HTML_Tag_Processor( '<div class="test">Test</div>' );
+ * $processor->next_tag() === true;
+ * $processor->get_tag() === 'DIV';
+ *
+ * $processor->next_tag() === false;
+ * $processor->get_tag() === null;
+ *
+ * @since 6.4.0
+ *
+ * @return string|null Name of currently matched tag in input HTML, or `null` if none found.
+ */
+ public function get_tag() {
+ if ( null !== $this->last_error ) {
+ return null;
+ }
+
+ $tag_name = parent::get_tag();
+
+ switch ( $tag_name ) {
+ case 'IMAGE':
+ /*
+ * > A start tag whose tag name is "image"
+ * > Change the token's tag name to "img" and reprocess it. (Don't ask.)
+ */
+ return 'IMG';
+
+ default:
+ return $tag_name;
+ }
+ }
+
+ /**
+ * Removes a bookmark that is no longer needed.
+ *
+ * Releasing a bookmark frees up the small
+ * performance overhead it requires.
+ *
+ * @since 6.4.0
+ *
+ * @param string $bookmark_name Name of the bookmark to remove.
+ * @return bool Whether the bookmark already existed before removal.
+ */
+ public function release_bookmark( $bookmark_name ) {
+ return parent::release_bookmark( "_{$bookmark_name}" );
+ }
+
+ /**
+ * Moves the internal cursor in the HTML Processor to a given bookmark's location.
+ *
+ * In order to prevent accidental infinite loops, there's a
+ * maximum limit on the number of times seek() can be called.
+ *
+ * @throws Exception When unable to allocate a bookmark for the next token in the input HTML document.
+ *
+ * @since 6.4.0
+ *
+ * @param string $bookmark_name Jump to the place in the document identified by this bookmark name.
+ * @return bool Whether the internal cursor was successfully moved to the bookmark's location.
+ */
+ public function seek( $bookmark_name ) {
+ $actual_bookmark_name = "_{$bookmark_name}";
+ $processor_started_at = $this->state->current_token
+ ? $this->bookmarks[ $this->state->current_token->bookmark_name ]->start
+ : 0;
+ $bookmark_starts_at = $this->bookmarks[ $actual_bookmark_name ]->start;
+ $direction = $bookmark_starts_at > $processor_started_at ? 'forward' : 'backward';
+
+ switch ( $direction ) {
+ case 'forward':
+ // When moving forwards, re-parse the document until reaching the same location as the original bookmark.
+ while ( $this->step() ) {
+ if ( $bookmark_starts_at === $this->bookmarks[ $this->state->current_token->bookmark_name ]->start ) {
+ return true;
+ }
+ }
+
+ return false;
+
+ case 'backward':
+ /*
+ * When moving backwards, clear out all existing stack entries which appear after the destination
+ * bookmark. These could be stored for later retrieval, but doing so would require additional
+ * memory overhead and also demand that references and bookmarks are updated as the document
+ * changes. In time this could be a valuable optimization, but it's okay to give up that
+ * optimization in exchange for more CPU time to recompute the stack, to re-parse the
+ * document that may have already been parsed once.
+ */
+ foreach ( $this->state->stack_of_open_elements->walk_up() as $item ) {
+ if ( $bookmark_starts_at >= $this->bookmarks[ $item->bookmark_name ]->start ) {
+ break;
+ }
+
+ $this->state->stack_of_open_elements->remove_node( $item );
+ }
+
+ foreach ( $this->state->active_formatting_elements->walk_up() as $item ) {
+ if ( $bookmark_starts_at >= $this->bookmarks[ $item->bookmark_name ]->start ) {
+ break;
+ }
+
+ $this->state->active_formatting_elements->remove_node( $item );
+ }
+
+ return parent::seek( $actual_bookmark_name );
+ }
+ }
+
+ /**
+ * Sets a bookmark in the HTML document.
+ *
+ * Bookmarks represent specific places or tokens in the HTML
+ * document, such as a tag opener or closer. When applying
+ * edits to a document, such as setting an attribute, the
+ * text offsets of that token may shift; the bookmark is
+ * kept updated with those shifts and remains stable unless
+ * the entire span of text in which the token sits is removed.
+ *
+ * Release bookmarks when they are no longer needed.
+ *
+ * Example:
+ *
+ * <main><h2>Surprising fact you may not know!</h2></main>
+ * ^ ^
+ * \-|-- this `H2` opener bookmark tracks the token
+ *
+ * <main class="clickbait"><h2>Surprising fact you may no…
+ * ^ ^
+ * \-|-- it shifts with edits
+ *
+ * Bookmarks provide the ability to seek to a previously-scanned
+ * place in the HTML document. This avoids the need to re-scan
+ * the entire document.
+ *
+ * Example:
+ *
+ * <ul><li>One</li><li>Two</li><li>Three</li></ul>
+ * ^^^^
+ * want to note this last item
+ *
+ * $p = new WP_HTML_Tag_Processor( $html );
+ * $in_list = false;
+ * while ( $p->next_tag( array( 'tag_closers' => $in_list ? 'visit' : 'skip' ) ) ) {
+ * if ( 'UL' === $p->get_tag() ) {
+ * if ( $p->is_tag_closer() ) {
+ * $in_list = false;
+ * $p->set_bookmark( 'resume' );
+ * if ( $p->seek( 'last-li' ) ) {
+ * $p->add_class( 'last-li' );
+ * }
+ * $p->seek( 'resume' );
+ * $p->release_bookmark( 'last-li' );
+ * $p->release_bookmark( 'resume' );
+ * } else {
+ * $in_list = true;
+ * }
+ * }
+ *
+ * if ( 'LI' === $p->get_tag() ) {
+ * $p->set_bookmark( 'last-li' );
+ * }
+ * }
+ *
+ * Bookmarks intentionally hide the internal string offsets
+ * to which they refer. They are maintained internally as
+ * updates are applied to the HTML document and therefore
+ * retain their "position" - the location to which they
+ * originally pointed. The inability to use bookmarks with
+ * functions like `substr` is therefore intentional to guard
+ * against accidentally breaking the HTML.
+ *
+ * Because bookmarks allocate memory and require processing
+ * for every applied update, they are limited and require
+ * a name. They should not be created with programmatically-made
+ * names, such as "li_{$index}" with some loop. As a general
+ * rule they should only be created with string-literal names
+ * like "start-of-section" or "last-paragraph".
+ *
+ * Bookmarks are a powerful tool to enable complicated behavior.
+ * Consider double-checking that you need this tool if you are
+ * reaching for it, as inappropriate use could lead to broken
+ * HTML structure or unwanted processing overhead.
+ *
+ * @since 6.4.0
+ *
+ * @param string $bookmark_name Identifies this particular bookmark.
+ * @return bool Whether the bookmark was successfully created.
+ */
+ public function set_bookmark( $bookmark_name ) {
+ return parent::set_bookmark( "_{$bookmark_name}" );
+ }
+
+ /*
+ * HTML Parsing Algorithms
+ */
+
+ /**
+ * Closes a P element.
+ *
+ * @since 6.4.0
+ *
+ * @throws WP_HTML_Unsupported_Exception When encountering unsupported HTML input.
+ *
+ * @see https://html.spec.whatwg.org/#close-a-p-element
+ */
+ private function close_a_p_element() {
+ $this->generate_implied_end_tags( 'P' );
+ $this->state->stack_of_open_elements->pop_until( 'P' );
+ }
+
+ /**
+ * Closes elements that have implied end tags.
+ *
+ * @since 6.4.0
+ *
+ * @see https://html.spec.whatwg.org/#generate-implied-end-tags
+ *
+ * @param string|null $except_for_this_element Perform as if this element doesn't exist in the stack of open elements.
+ */
+ private function generate_implied_end_tags( $except_for_this_element = null ) {
+ $elements_with_implied_end_tags = array(
+ 'P',
+ );
+
+ $current_node = $this->state->stack_of_open_elements->current_node();
+ while (
+ $current_node && $current_node->node_name !== $except_for_this_element &&
+ in_array( $this->state->stack_of_open_elements->current_node(), $elements_with_implied_end_tags, true )
+ ) {
+ $this->state->stack_of_open_elements->pop();
+ }
+ }
+
+ /**
+ * Closes elements that have implied end tags, thoroughly.
+ *
+ * See the HTML specification for an explanation why this is
+ * different from generating end tags in the normal sense.
+ *
+ * @since 6.4.0
+ *
+ * @see WP_HTML_Processor::generate_implied_end_tags
+ * @see https://html.spec.whatwg.org/#generate-implied-end-tags
+ */
+ private function generate_implied_end_tags_thoroughly() {
+ $elements_with_implied_end_tags = array(
+ 'P',
+ );
+
+ while ( in_array( $this->state->stack_of_open_elements->current_node(), $elements_with_implied_end_tags, true ) ) {
+ $this->state->stack_of_open_elements->pop();
+ }
+ }
+
+ /**
+ * Reconstructs the active formatting elements.
+ *
+ * > This has the effect of reopening all the formatting elements that were opened
+ * > in the current body, cell, or caption (whichever is youngest) that haven't
+ * > been explicitly closed.
+ *
+ * @since 6.4.0
+ *
+ * @throws WP_HTML_Unsupported_Exception When encountering unsupported HTML input.
+ *
+ * @see https://html.spec.whatwg.org/#reconstruct-the-active-formatting-elements
+ *
+ * @return bool Whether any formatting elements needed to be reconstructed.
+ */
+ private function reconstruct_active_formatting_elements() {
+ /*
+ * > If there are no entries in the list of active formatting elements, then there is nothing
+ * > to reconstruct; stop this algorithm.
+ */
+ if ( 0 === $this->state->active_formatting_elements->count() ) {
+ return false;
+ }
+
+ $last_entry = $this->state->active_formatting_elements->current_node();
+ if (
+
+ /*
+ * > If the last (most recently added) entry in the list of active formatting elements is a marker;
+ * > stop this algorithm.
+ */
+ 'marker' === $last_entry->node_name ||
+
+ /*
+ * > If the last (most recently added) entry in the list of active formatting elements is an
+ * > element that is in the stack of open elements, then there is nothing to reconstruct;
+ * > stop this algorithm.
+ */
+ $this->state->stack_of_open_elements->contains_node( $last_entry )
+ ) {
+ return false;
+ }
+
+ $this->last_error = self::ERROR_UNSUPPORTED;
+ throw new WP_HTML_Unsupported_Exception( 'Cannot reconstruct active formatting elements when advancing and rewinding is required.' );
+ }
+
+ /**
+ * Runs the adoption agency algorithm.
+ *
+ * @since 6.4.0
+ *
+ * @throws WP_HTML_Unsupported_Exception When encountering unsupported HTML input.
+ *
+ * @see https://html.spec.whatwg.org/#adoption-agency-algorithm
+ */
+ private function run_adoption_agency_algorithm() {
+ $budget = 1000;
+ $subject = $this->get_tag();
+ $current_node = $this->state->stack_of_open_elements->current_node();
+
+ if (
+ // > If the current node is an HTML element whose tag name is subject
+ $current_node && $subject === $current_node->node_name &&
+ // > the current node is not in the list of active formatting elements
+ ! $this->state->active_formatting_elements->contains_node( $current_node )
+ ) {
+ $this->state->stack_of_open_elements->pop();
+ return;
+ }
+
+ $outer_loop_counter = 0;
+ while ( $budget-- > 0 ) {
+ if ( $outer_loop_counter++ >= 8 ) {
+ return;
+ }
+
+ /*
+ * > Let formatting element be the last element in the list of active formatting elements that:
+ * > - is between the end of the list and the last marker in the list,
+ * > if any, or the start of the list otherwise,
+ * > - and has the tag name subject.
+ */
+ $formatting_element = null;
+ foreach ( $this->state->active_formatting_elements->walk_up() as $item ) {
+ if ( 'marker' === $item->node_name ) {
+ break;
+ }
+
+ if ( $subject === $item->node_name ) {
+ $formatting_element = $item;
+ break;
+ }
+ }
+
+ // > If there is no such element, then return and instead act as described in the "any other end tag" entry above.
+ if ( null === $formatting_element ) {
+ $this->last_error = self::ERROR_UNSUPPORTED;
+ throw new WP_HTML_Unsupported_Exception( 'Cannot run adoption agency when "any other end tag" is required.' );
+ }
+
+ // > If formatting element is not in the stack of open elements, then this is a parse error; remove the element from the list, and return.
+ if ( ! $this->state->stack_of_open_elements->contains_node( $formatting_element ) ) {
+ $this->state->active_formatting_elements->remove_node( $formatting_element->bookmark_name );
+ return;
+ }
+
+ // > If formatting element is in the stack of open elements, but the element is not in scope, then this is a parse error; return.
+ if ( ! $this->state->stack_of_open_elements->has_element_in_scope( $formatting_element->node_name ) ) {
+ return;
+ }
+
+ /*
+ * > Let furthest block be the topmost node in the stack of open elements that is lower in the stack
+ * > than formatting element, and is an element in the special category. There might not be one.
+ */
+ $is_above_formatting_element = true;
+ $furthest_block = null;
+ foreach ( $this->state->stack_of_open_elements->walk_down() as $item ) {
+ if ( $is_above_formatting_element && $formatting_element->bookmark_name !== $item->bookmark_name ) {
+ continue;
+ }
+
+ if ( $is_above_formatting_element ) {
+ $is_above_formatting_element = false;
+ continue;
+ }
+
+ if ( self::is_special( $item->node_name ) ) {
+ $furthest_block = $item;
+ break;
+ }
+ }
+
+ /*
+ * > If there is no furthest block, then the UA must first pop all the nodes from the bottom of the
+ * > stack of open elements, from the current node up to and including formatting element, then
+ * > remove formatting element from the list of active formatting elements, and finally return.
+ */
+ if ( null === $furthest_block ) {
+ foreach ( $this->state->stack_of_open_elements->walk_up() as $item ) {
+ $this->state->stack_of_open_elements->pop();
+
+ if ( $formatting_element->bookmark_name === $item->bookmark_name ) {
+ $this->state->active_formatting_elements->remove_node( $formatting_element );
+ return;
+ }
+ }
+ }
+
+ $this->last_error = self::ERROR_UNSUPPORTED;
+ throw new WP_HTML_Unsupported_Exception( 'Cannot extract common ancestor in adoption agency algorithm.' );
+ }
+
+ $this->last_error = self::ERROR_UNSUPPORTED;
+ throw new WP_HTML_Unsupported_Exception( 'Cannot run adoption agency when looping required.' );
+ }
+
+ /**
+ * Inserts an HTML element on the stack of open elements.
+ *
+ * @since 6.4.0
+ *
+ * @see https://html.spec.whatwg.org/#insert-a-foreign-element
+ *
+ * @param WP_HTML_Token $token Name of bookmark pointing to element in original input HTML.
+ */
+ private function insert_html_element( $token ) {
+ $this->state->stack_of_open_elements->push( $token );
+ }
+
+ /*
+ * HTML Specification Helpers
+ */
+
+ /**
+ * Returns whether an element of a given name is in the HTML special category.
+ *
+ * @since 6.4.0
+ *
+ * @see https://html.spec.whatwg.org/#special
+ *
+ * @param string $tag_name Name of element to check.
+ * @return bool Whether the element of the given name is in the special category.
+ */
+ public static function is_special( $tag_name ) {
+ $tag_name = strtoupper( $tag_name );
+
+ return (
+ 'ADDRESS' === $tag_name ||
+ 'APPLET' === $tag_name ||
+ 'AREA' === $tag_name ||
+ 'ARTICLE' === $tag_name ||
+ 'ASIDE' === $tag_name ||
+ 'BASE' === $tag_name ||
+ 'BASEFONT' === $tag_name ||
+ 'BGSOUND' === $tag_name ||
+ 'BLOCKQUOTE' === $tag_name ||
+ 'BODY' === $tag_name ||
+ 'BR' === $tag_name ||
+ 'BUTTON' === $tag_name ||
+ 'CAPTION' === $tag_name ||
+ 'CENTER' === $tag_name ||
+ 'COL' === $tag_name ||
+ 'COLGROUP' === $tag_name ||
+ 'DD' === $tag_name ||
+ 'DETAILS' === $tag_name ||
+ 'DIR' === $tag_name ||
+ 'DIV' === $tag_name ||
+ 'DL' === $tag_name ||
+ 'DT' === $tag_name ||
+ 'EMBED' === $tag_name ||
+ 'FIELDSET' === $tag_name ||
+ 'FIGCAPTION' === $tag_name ||
+ 'FIGURE' === $tag_name ||
+ 'FOOTER' === $tag_name ||
+ 'FORM' === $tag_name ||
+ 'FRAME' === $tag_name ||
+ 'FRAMESET' === $tag_name ||
+ 'H1' === $tag_name ||
+ 'H2' === $tag_name ||
+ 'H3' === $tag_name ||
+ 'H4' === $tag_name ||
+ 'H5' === $tag_name ||
+ 'H6' === $tag_name ||
+ 'HEAD' === $tag_name ||
+ 'HEADER' === $tag_name ||
+ 'HGROUP' === $tag_name ||
+ 'HR' === $tag_name ||
+ 'HTML' === $tag_name ||
+ 'IFRAME' === $tag_name ||
+ 'IMG' === $tag_name ||
+ 'INPUT' === $tag_name ||
+ 'KEYGEN' === $tag_name ||
+ 'LI' === $tag_name ||
+ 'LINK' === $tag_name ||
+ 'LISTING' === $tag_name ||
+ 'MAIN' === $tag_name ||
+ 'MARQUEE' === $tag_name ||
+ 'MENU' === $tag_name ||
+ 'META' === $tag_name ||
+ 'NAV' === $tag_name ||
+ 'NOEMBED' === $tag_name ||
+ 'NOFRAMES' === $tag_name ||
+ 'NOSCRIPT' === $tag_name ||
+ 'OBJECT' === $tag_name ||
+ 'OL' === $tag_name ||
+ 'P' === $tag_name ||
+ 'PARAM' === $tag_name ||
+ 'PLAINTEXT' === $tag_name ||
+ 'PRE' === $tag_name ||
+ 'SCRIPT' === $tag_name ||
+ 'SEARCH' === $tag_name ||
+ 'SECTION' === $tag_name ||
+ 'SELECT' === $tag_name ||
+ 'SOURCE' === $tag_name ||
+ 'STYLE' === $tag_name ||
+ 'SUMMARY' === $tag_name ||
+ 'TABLE' === $tag_name ||
+ 'TBODY' === $tag_name ||
+ 'TD' === $tag_name ||
+ 'TEMPLATE' === $tag_name ||
+ 'TEXTAREA' === $tag_name ||
+ 'TFOOT' === $tag_name ||
+ 'TH' === $tag_name ||
+ 'THEAD' === $tag_name ||
+ 'TITLE' === $tag_name ||
+ 'TR' === $tag_name ||
+ 'TRACK' === $tag_name ||
+ 'UL' === $tag_name ||
+ 'WBR' === $tag_name ||
+ 'XMP' === $tag_name ||
+
+ // MathML.
+ 'MI' === $tag_name ||
+ 'MO' === $tag_name ||
+ 'MN' === $tag_name ||
+ 'MS' === $tag_name ||
+ 'MTEXT' === $tag_name ||
+ 'ANNOTATION-XML' === $tag_name ||
+
+ // SVG.
+ 'FOREIGNOBJECT' === $tag_name ||
+ 'DESC' === $tag_name ||
+ 'TITLE' === $tag_name
+ );
+ }
+
+ /**
+ * Returns whether a given element is an HTML Void Element
+ *
+ * > area, base, br, col, embed, hr, img, input, link, meta, source, track, wbr
+ *
+ * @since 6.4.0
+ *
+ * @see https://html.spec.whatwg.org/#void-elements
+ *
+ * @param string $tag_name Name of HTML tag to check.
+ * @return bool Whether the given tag is an HTML Void Element.
+ */
+ public static function is_void( $tag_name ) {
+ $tag_name = strtoupper( $tag_name );
+
+ return (
+ 'AREA' === $tag_name ||
+ 'BASE' === $tag_name ||
+ 'BR' === $tag_name ||
+ 'COL' === $tag_name ||
+ 'EMBED' === $tag_name ||
+ 'HR' === $tag_name ||
+ 'IMG' === $tag_name ||
+ 'INPUT' === $tag_name ||
+ 'LINK' === $tag_name ||
+ 'META' === $tag_name ||
+ 'SOURCE' === $tag_name ||
+ 'TRACK' === $tag_name ||
+ 'WBR' === $tag_name
+ );
+ }
+
+ /*
+ * Constants that would pollute the top of the class if they were found there.
+ */
+
+ /**
+ * Indicates that the next HTML token should be parsed and processed.
+ *
+ * @since 6.4.0
+ *
+ * @var string
+ */
+ const PROCESS_NEXT_NODE = 'process-next-node';
+
+ /**
+ * Indicates that the current HTML token should be reprocessed in the newly-selected insertion mode.
+ *
+ * @since 6.4.0
+ *
+ * @var string
+ */
+ const REPROCESS_CURRENT_NODE = 'reprocess-current-node';
+
+ /**
+ * Indicates that the parser encountered unsupported markup and has bailed.
+ *
+ * @since 6.4.0
+ *
+ * @var string
+ */
+ const ERROR_UNSUPPORTED = 'unsupported';
+
+ /**
+ * Indicates that the parser encountered more HTML tokens than it
+ * was able to process and has bailed.
+ *
+ * @since 6.4.0
+ *
+ * @var string
+ */
+ const ERROR_EXCEEDED_MAX_BOOKMARKS = 'exceeded-max-bookmarks';
+
+ /**
+ * Unlock code that must be passed into the constructor to create this class.
+ *
+ * This class extends the WP_HTML_Tag_Processor, which has a public class
+ * constructor. Therefore, it's not possible to have a private constructor here.
+ *
+ * This unlock code is used to ensure that anyone calling the constructor is
+ * doing so with a full understanding that it's intended to be a private API.
+ *
+ * @access private
+ */
+ const CONSTRUCTOR_UNLOCK_CODE = 'Use WP_HTML_Processor::create_fragment() instead of calling the class constructor directly.';
+}