Work on fix

src/wp-includes/html-api/class-wp-html-processor.php

@@ -5286,6 +5286,8 @@ public function seek( $bookmark_name ): bool {
 		// Flush any pending updates to the document before beginning.
 		$this->get_updated_html();
 
+		echo 'Seeking to ' . $bookmark_name . "\n";
+
 		$actual_bookmark_name = "_{$bookmark_name}";
 		$processor_started_at = $this->state->current_token
 			? $this->bookmarks[ $this->state->current_token->bookmark_name ]->start
@@ -5323,45 +5325,64 @@ public function seek( $bookmark_name ): bool {
 		 * and computation time.
 		 */
 		if ( 'backward' === $direction ) {
-			/*
-			 * Instead of clearing the parser state and starting fresh, calling the stack methods
-			 * maintains the proper flags in the parser.
-			 */
-			foreach ( $this->state->stack_of_open_elements->walk_up() as $item ) {
-				if ( 'context-node' === $item->bookmark_name ) {
-					break;
-				}
+			echo 'back: ' . "\n";
+			// Reset necessary parser state
+			$this->state->frameset_ok                       = true;
+			$this->state->stack_of_template_insertion_modes = array();
+			$this->state->head_element                      = null;
+			$this->state->form_element                      = null;
+			$this->state->current_token                     = null;
+			$this->element_queue                            = array();
+			$this->current_element                          = null;
+
+			if ( null === $this->context_node ) {
+				echo 'full parser' . "\n";
+				/*
+				 * In the case of a full parser, the processor needs to be
+				 * reset to a clean state and start over.
+				 */
+				$this->state->stack_of_open_elements     = new WP_HTML_Open_Elements();
+				$this->state->active_formatting_elements = new WP_HTML_Active_Formatting_Elements();
 
-				$this->state->stack_of_open_elements->remove_node( $item );
-			}
+				$this->breadcrumbs          = array();
+				$this->bytes_already_parsed = 0;
+				$this->parser_state         = self::STATE_READY;
+			} else {
+				/*
+				 * In case the parser is a fragment parser, instead of clearing the
+				 * parser state and starting fresh, calling the stack methods
+				 * maintains the proper flags in the parser.
+				 */
+				foreach ( $this->state->stack_of_open_elements->walk_up() as $item ) {
+					if ( 'context-node' === $item->bookmark_name ) {
+						break;
+					}
 
-			foreach ( $this->state->active_formatting_elements->walk_up() as $item ) {
-				if ( 'context-node' === $item->bookmark_name ) {
-					break;
+					$this->state->stack_of_open_elements->remove_node( $item );
 				}
 
-				$this->state->active_formatting_elements->remove_node( $item );
-			}
+				foreach ( $this->state->active_formatting_elements->walk_up() as $item ) {
+					if ( 'context-node' === $item->bookmark_name ) {
+						break;
+					}
 
-			parent::seek( 'context-node' );
-			$this->state->insertion_mode = WP_HTML_Processor_State::INSERTION_MODE_IN_BODY;
-			$this->state->frameset_ok    = true;
-			$this->element_queue         = array();
-			$this->current_element       = null;
+					$this->state->active_formatting_elements->remove_node( $item );
+				}
 
-			if ( isset( $this->context_node ) ) {
-				$this->breadcrumbs = array_slice( $this->breadcrumbs, 0, 2 );
-			} else {
-				$this->breadcrumbs = array();
+				parent::seek( 'context-node' );
+				$this->state->insertion_mode = WP_HTML_Processor_State::INSERTION_MODE_IN_BODY;
+				$this->breadcrumbs           = array_slice( $this->breadcrumbs, 0, 2 );
 			}
 		}
 
+
 		// When moving forwards, reparse the document until reaching the same location as the original bookmark.
-		if ( $bookmark_starts_at === $this->bookmarks[ $this->state->current_token->bookmark_name ]->start ) {
+		if ( null !== $this->state->current_token && $bookmark_starts_at === $this->bookmarks[ $this->state->current_token->bookmark_name ]->start ) {
 			return true;
 		}
 
 		while ( $this->next_token() ) {
+			echo 'bm starts at ' . $bookmark_starts_at . ' and current token starts at ' . $this->bookmarks[ $this->state->current_token->bookmark_name ]->start . "\n";
 			if ( $bookmark_starts_at === $this->bookmarks[ $this->state->current_token->bookmark_name ]->start ) {
 				while ( isset( $this->current_element ) && WP_HTML_Stack_Event::POP === $this->current_element->operation ) {
 					$this->current_element = array_shift( $this->element_queue );
@@ -5370,6 +5391,7 @@ public function seek( $bookmark_name ): bool {
 			}
 		}
 
+	echo 'false' . "\n";
 		return false;
 	}
 

src/wp-includes/html-api/class-wp-html-tag-processor.php

@@ -591,7 +591,7 @@ class WP_HTML_Tag_Processor {
 	 * @since 6.2.0
 	 * @var int
 	 */
-	private $bytes_already_parsed = 0;
+	protected $bytes_already_parsed = 0;
 
 	/**
 	 * Byte offset in input document where current token starts.
@@ -946,6 +946,8 @@ private function base_class_next_token(): bool {
 		$was_at = $this->bytes_already_parsed;
 		$this->after_tag();
 
+		var_dump( $was_at, $this->parser_state );
+
 		// Don't proceed if there's nothing more to scan.
 		if (
 			self::STATE_COMPLETE === $this->parser_state ||
@@ -2542,6 +2544,7 @@ public function has_bookmark( $bookmark_name ): bool {
 	 * @return bool Whether the internal cursor was successfully moved to the bookmark's location.
 	 */
 	public function seek( $bookmark_name ): bool {
+		var_dump( $bookmark_name, $this->bookmarks );
 		if ( ! array_key_exists( $bookmark_name, $this->bookmarks ) ) {
 			_doing_it_wrong(
 				__METHOD__,