HTML API: Add bookmark invalidation logic.

While `WP_HTML_Tag_Processor` currently only supports changing a given tag's attributes, the plan is to provide methods to make broader changes (possibly through a subclass of `WP_HTML_Tag_Processor`). The API will have the potential of replacing a tag that a bookmark points to. To prepare, this changeset makes sure that all bookmarks affected by a HTML replacement are invalidated (i.e. released).

Changes:
* Extends the existing loop in `WP_HTML_Tag_Processor::apply_attributes_updates()` that adjusts bookmarks' start and end positions upon HTML changes to check if the entire bookmark is within a portion of the HTML that has been replaced.
* Adds `WP_HTML_Tag_Processor::has_bookmark() to check whether the given bookmark name exists.

References:
* [WordPress/gutenberg#47559 Gutenberg PR 47559]
* [https://github.com/WordPress/gutenberg/releases/tag/v15.3.0 Released in Gutenberg 15.3.0]

Follow-up to [55203].

Props bernhard-reiter, dmsnell, zieladam.
Fixes #57788.

git-svn-id: https://develop.svn.wordpress.org/trunk@55555 602fd350-edb4-49c9-b593-d223f7449a82

Author: hellofromtonya

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

@@ -1404,6 +1404,7 @@ private function class_name_updates_to_attributes_updates() {
 	 * Applies attribute updates to HTML document.
 	 *
 	 * @since 6.2.0
+	 * @since 6.3.0 Invalidate any bookmarks whose targets are overwritten.
 	 *
 	 * @return void
 	 */
@@ -1434,7 +1435,7 @@ private function apply_attributes_updates() {
 		 * Adjust bookmark locations to account for how the text
 		 * replacements adjust offsets in the input document.
 		 */
-		foreach ( $this->bookmarks as $bookmark ) {
+		foreach ( $this->bookmarks as $bookmark_name => $bookmark ) {
 			/*
 			 * Each lexical update which appears before the bookmark's endpoints
 			 * might shift the offsets for those endpoints. Loop through each change
@@ -1445,20 +1446,22 @@ private function apply_attributes_updates() {
 			$tail_delta = 0;
 
 			foreach ( $this->lexical_updates as $diff ) {
-				$update_head = $bookmark->start >= $diff->start;
-				$update_tail = $bookmark->end >= $diff->start;
-
-				if ( ! $update_head && ! $update_tail ) {
+				if ( $bookmark->start < $diff->start && $bookmark->end < $diff->start ) {
 					break;
 				}
 
+				if ( $bookmark->start >= $diff->start && $bookmark->end < $diff->end ) {
+					$this->release_bookmark( $bookmark_name );
+					continue 2;
+				}
+
 				$delta = strlen( $diff->text ) - ( $diff->end - $diff->start );
 
-				if ( $update_head ) {
+				if ( $bookmark->start >= $diff->start ) {
 					$head_delta += $delta;
 				}
 
-				if ( $update_tail ) {
+				if ( $bookmark->end >= $diff->end ) {
 					$tail_delta += $delta;
 				}
 			}
@@ -1470,6 +1473,18 @@ private function apply_attributes_updates() {
 		$this->lexical_updates = array();
 	}
 
+	/**
+	 * Checks whether a bookmark with the given name exists.
+	 *
+	 * @since 6.3.0
+	 *
+	 * @param string $bookmark_name Name to identify a bookmark that potentially exists.
+	 * @return bool Whether that bookmark exists.
+	 */
+	public function has_bookmark( $bookmark_name ) {
+		return array_key_exists( $bookmark_name, $this->bookmarks );
+	}
+
 	/**
 	 * Move the internal cursor in the Tag Processor to a given bookmark's location.
 	 *

tests/phpunit/tests/html-api/wpHtmlTagProcessor-bookmark.php

@@ -40,6 +40,41 @@ public function test_release_bookmark() {
 		$this->assertTrue( $p->release_bookmark( 'first li' ), 'Could not release a bookmark' );
 	}
 
+	/**
+	 * @ticket 57788
+	 *
+	 * @covers WP_HTML_Tag_Processor::has_bookmark
+	 */
+	public function test_has_bookmark_returns_false_if_bookmark_does_not_exist() {
+		$p = new WP_HTML_Tag_Processor( '<div>Test</div>' );
+		$this->assertFalse( $p->has_bookmark( 'my-bookmark' ) );
+	}
+
+	/**
+	 * @ticket 57788
+	 *
+	 * @covers WP_HTML_Tag_Processor::has_bookmark
+	 */
+	public function test_has_bookmark_returns_true_if_bookmark_exists() {
+		$p = new WP_HTML_Tag_Processor( '<div>Test</div>' );
+		$p->next_tag();
+		$p->set_bookmark( 'my-bookmark' );
+		$this->assertTrue( $p->has_bookmark( 'my-bookmark' ) );
+	}
+
+	/**
+	 * @ticket 57788
+	 *
+	 * @covers WP_HTML_Tag_Processor::has_bookmark
+	 */
+	public function test_has_bookmark_returns_false_if_bookmark_has_been_released() {
+		$p = new WP_HTML_Tag_Processor( '<div>Test</div>' );
+		$p->next_tag();
+		$p->set_bookmark( 'my-bookmark' );
+		$p->release_bookmark( 'my-bookmark' );
+		$this->assertFalse( $p->has_bookmark( 'my-bookmark' ) );
+	}
+
 	/**
 	 * @ticket 56299
 	 *