From beda2c383ae588db8c8a11c5f1e505ef06b27e83 Mon Sep 17 00:00:00 2001
From: Dennis Snell <dennis.snell@automattic.com>
Date: Tue, 21 Feb 2023 15:02:49 -0700
Subject: [PATCH 01/20] WIP: Introduce directive processor

The directive processor builds on the HTML Tag Processor to provide additional functionality, assuming
normative markup generated from React, assuming that all tag directives contain a balanced closer.

This will break in practice, and is probably entirely wrong as-is. The purpose of this commit is to
introduce the idea and explore using the code to get a feel for whether it will work.
---
 src/class-wp-directive-processor.php | 92 ++++++++++++++++++++++++++++
 1 file changed, 92 insertions(+)
 create mode 100644 src/class-wp-directive-processor.php

diff --git a/src/class-wp-directive-processor.php b/src/class-wp-directive-processor.php
new file mode 100644
index 00000000..1a346efb
--- /dev/null
+++ b/src/class-wp-directive-processor.php
@@ -0,0 +1,92 @@
+<?php
+
+class WP_Directive_Processor extends WP_HTML_Tag_Processor {
+	const DIRECTIVE_PREFIX = 'WPX-';
+
+	public $html;
+
+	public $might_have_directives = true;
+
+	public function __construct( $html ) {
+		parent::__construct( $html );
+
+		if ( false === stripos( self::DIRECTIVE_PREFIX, $html ) ) {
+			$this->might_have_directives = false;
+		}
+	}
+
+	public function next_directive() {
+		if ( false === $this->might_have_directives ) {
+			return false;
+		}
+
+		while ( $this->next_tag( array( 'tag_closers' => 'visit' ) ) ) {
+			$tag_name = $this->get_tag();
+			if ( 0 === stripos( self::DIRECTIVE_PREFIX, $tag_name ) ) {
+				return true;
+			}
+
+			$attribute_directives = $this->get_attribute_names_with_prefix( self::DIRECTIVE_PREFIX );
+			if ( 0 < count( $attribute_directives ) ) {
+				return true;
+			}
+		}
+
+		return false;
+	}
+
+	public function next_balanced_closer() {
+		$depth = 0;
+
+		$tag_name = $this->get_tag();
+		while ( $this->next_tag( array( 'tag_name' => $tag_name, 'tag_closers' => 'visit' ) ) ) {
+			if ( ! $this->is_tag_closer() ) {
+				$depth++;
+				continue;
+			}
+
+			if ( 0 === $depth ) {
+				return true;
+			}
+
+			$depth--;
+		}
+
+		return false;
+	}
+
+	public function get_inner_html() {
+		$this->set_bookmark( 'start' );
+		if ( ! $this->next_balanced_closer() ) {
+			$this->release_bookmark( 'start' );
+			return false;
+		}
+		$this->set_bookmark( 'end' );
+
+		$start = $this->bookmarks['start']->end + 1;
+		$end   = $this->bookmarks['end']->start;
+
+		$this->release_bookmark( 'start' );
+		$this->release_bookmark( 'end' );
+
+		return substr( $this->html, $start, $end - $start );
+	}
+
+	public function set_inner_html( $new_html ) {
+		$this->set_bookmark( 'start' );
+		if ( ! $this->next_balanced_closer() ) {
+			$this->release_bookmark( 'start' );
+			return false;
+		}
+		$this->set_bookmark( 'end' );
+
+		$start = $this->bookmarks['start']->end + 1;
+		$end   = $this->bookmarks['end']->start;
+
+		$this->release_bookmark( 'start' );
+		$this->release_bookmark( 'end' );
+
+		$this->lexical_updates[] = new WP_HTML_Text_Replacement( $start, $end, $new_html );
+		return true;
+	}
+}
\ No newline at end of file

From 4e4b983a3c5c8c72d267ca5edcce682595ede12a Mon Sep 17 00:00:00 2001
From: Bernie Reiter <ockham@raz.or.at>
Date: Thu, 2 Mar 2023 12:13:50 +0100
Subject: [PATCH 02/20] Move to directives/ dir

---
 src/{ => directives}/class-wp-directive-processor.php | 0
 1 file changed, 0 insertions(+), 0 deletions(-)
 rename src/{ => directives}/class-wp-directive-processor.php (100%)

diff --git a/src/class-wp-directive-processor.php b/src/directives/class-wp-directive-processor.php
similarity index 100%
rename from src/class-wp-directive-processor.php
rename to src/directives/class-wp-directive-processor.php

From f85a7d366842293caca89d133190946b0d3d1fa1 Mon Sep 17 00:00:00 2001
From: Bernie Reiter <ockham@raz.or.at>
Date: Thu, 2 Mar 2023 12:14:03 +0100
Subject: [PATCH 03/20] Add basic test coverage

---
 phpunit/directives/wp-directive-processor.php | 98 +++++++++++++++++++
 1 file changed, 98 insertions(+)
 create mode 100644 phpunit/directives/wp-directive-processor.php

diff --git a/phpunit/directives/wp-directive-processor.php b/phpunit/directives/wp-directive-processor.php
new file mode 100644
index 00000000..83ba643c
--- /dev/null
+++ b/phpunit/directives/wp-directive-processor.php
@@ -0,0 +1,98 @@
+<?php
+/**
+ * `WP_Directive_Processor` class test.
+ */
+require_once __DIR__ . '/../../src/directives/class-wp-directive-processor.php';
+
+/**
+ * @group html-processor
+ *
+ * @coversDefaultClass WP_Directive_Processor
+ */
+class WP_Directive_Processor_Test extends WP_UnitTestCase {
+	const HTML = '<div>outside</div><section><div><img>inside</div></section>';
+
+	public function test_get_inner_html_returns_correct_result() {
+		$tags = new WP_Directive_Processor( self::HTML );
+
+		$tags->next_tag( 'section' );
+		$this->assertSame( '<div><img>inside</div>', $tags->get_inner_html() );
+	}
+
+	public function test_set_inner_html_on_void_element_has_no_effect() {
+		$tags = new WP_Directive_Processor( self::HTML );
+
+		$tags->next_tag( 'img' );
+		$content = $tags->set_inner_html( 'This is the new img content' );
+		$this->assertFalse( $content );
+		$this->assertSame( self::HTML, $tags->get_updated_html() );
+	}
+
+	public function test_set_inner_html_sets_content_correctly() {
+		$tags = new WP_Directive_Processor( self::HTML );
+
+		$tags->next_tag( 'section' );
+		$tags->set_inner_html( 'This is the new section content.' );
+		$this->assertSame( '<div>outside</div><section>This is the new section content.</section>', $tags->get_updated_html() );
+	}
+
+	public function test_set_inner_html_updates_bookmarks_correctly() {
+		$tags = new WP_Directive_Processor( self::HTML );
+
+		$tags->next_tag( 'div' );
+		$tags->set_bookmark( 'start' );
+		$tags->next_tag( 'img' );
+		$this->assertSame( 'IMG', $tags->get_tag() );
+		$tags->set_bookmark( 'after' );
+		$tags->seek( 'start' );
+
+		$tags->set_inner_html( 'This is the new div content.' );
+		$this->assertSame( '<div>This is the new div content.</div><section><div><img>inside</div></section>', $tags->get_updated_html() );
+		$tags->seek( 'after' );
+		$this->assertSame( 'IMG', $tags->get_tag() );
+	}
+
+	public function test_set_inner_html_subsequent_updates_on_the_same_tag_work() {
+		$tags = new WP_Directive_Processor( self::HTML );
+
+		$tags->next_tag( 'section' );
+		$tags->set_inner_html( 'This is the new section content.' );
+		$tags->set_inner_html( 'This is the even newer section content.' );
+		$this->assertSame( '<div>outside</div><section>This is the even newer section content.</section>', $tags->get_updated_html() );
+	}
+
+	public function test_set_inner_html_followed_by_set_attribute_works() {
+		$tags = new WP_Directive_Processor( self::HTML );
+
+		$tags->next_tag( 'section' );
+		$tags->set_inner_html( 'This is the new section content.' );
+		$tags->set_attribute( 'id', 'thesection' );
+		$this->assertSame( '<div>outside</div><section id="thesection">This is the new section content.</section>', $tags->get_updated_html() );
+	}
+
+	public function test_set_inner_html_preceded_by_set_attribute_works() {
+		$tags = new WP_Directive_Processor( self::HTML );
+
+		$tags->next_tag( 'section' );
+		$tags->set_attribute( 'id', 'thesection' );
+		$tags->set_inner_html( 'This is the new section content.' );
+		$this->assertSame( '<div>outside</div><section id="thesection">This is the new section content.</section>', $tags->get_updated_html() );
+	}
+
+	public function test_set_inner_html_invalidates_bookmarks_that_point_to_replaced_content() {
+		$tags = new WP_Directive_Processor( self::HTML );
+
+		$tags->next_tag( 'section' );
+		$tags->set_bookmark( 'start' );
+		$tags->next_tag( 'img' );
+		$tags->set_bookmark( 'replaced' );
+		$tags->seek( 'start' );
+
+		$tags->set_inner_html( 'This is the new section content.' );
+		$this->assertSame( '<div>outside</div><section>This is the new section content.</section>', $tags->get_updated_html() );
+
+		$this->expectExceptionMessage( 'Invalid bookmark name' );
+		$successful_seek = $tags->seek( 'replaced' );
+		$this->assertFalse( $successful_seek );
+	}
+}

From 9c25acba37a8ed0b6b3b91e8bc023be97869ca18 Mon Sep 17 00:00:00 2001
From: Bernie Reiter <ockham@raz.or.at>
Date: Thu, 2 Mar 2023 12:21:45 +0100
Subject: [PATCH 04/20] Add basic test for next_balanced_closer

---
 phpunit/directives/wp-directive-processor.php | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/phpunit/directives/wp-directive-processor.php b/phpunit/directives/wp-directive-processor.php
index 83ba643c..d391de2e 100644
--- a/phpunit/directives/wp-directive-processor.php
+++ b/phpunit/directives/wp-directive-processor.php
@@ -12,6 +12,15 @@
 class WP_Directive_Processor_Test extends WP_UnitTestCase {
 	const HTML = '<div>outside</div><section><div><img>inside</div></section>';
 
+	public function test_next_balanced_closer_proceeds_to_correct_tag() {
+		$tags = new WP_Directive_Processor( self::HTML );
+
+		$tags->next_tag( 'section' );
+		$tags->next_balanced_closer();
+		$this->assertSame( 'SECTION', $tags->get_tag() );
+		$this->assertTrue( $tags->is_tag_closer() );
+	}
+
 	public function test_get_inner_html_returns_correct_result() {
 		$tags = new WP_Directive_Processor( self::HTML );
 

From 3c95937fa45341292ad10655b203522567e071ed Mon Sep 17 00:00:00 2001
From: Bernie Reiter <ockham@raz.or.at>
Date: Thu, 2 Mar 2023 12:24:51 +0100
Subject: [PATCH 05/20] More test coverage for next_balanced_tag

---
 phpunit/directives/wp-directive-processor.php | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/phpunit/directives/wp-directive-processor.php b/phpunit/directives/wp-directive-processor.php
index d391de2e..8ca135de 100644
--- a/phpunit/directives/wp-directive-processor.php
+++ b/phpunit/directives/wp-directive-processor.php
@@ -21,6 +21,16 @@ public function test_next_balanced_closer_proceeds_to_correct_tag() {
 		$this->assertTrue( $tags->is_tag_closer() );
 	}
 
+    public function test_next_balanced_closer_proceeds_to_correct_tag_for_nested_tag() {
+		$tags = new WP_Directive_Processor( self::HTML );
+
+		$tags->next_tag( 'div' );
+		$tags->next_tag( 'div' );
+		$tags->next_balanced_closer();
+		$this->assertSame( 'DIV', $tags->get_tag() );
+		$this->assertTrue( $tags->is_tag_closer() );
+	}
+
 	public function test_get_inner_html_returns_correct_result() {
 		$tags = new WP_Directive_Processor( self::HTML );
 

From 52d15d7acbda2d67ce06e83373a32cfc16121bb4 Mon Sep 17 00:00:00 2001
From: Bernie Reiter <ockham@raz.or.at>
Date: Mon, 6 Mar 2023 17:12:27 +0100
Subject: [PATCH 06/20] TEMP: Use GB v15.3.0 RC2

---
 .wp-env.json | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.wp-env.json b/.wp-env.json
index f282f93d..47b4bbd9 100644
--- a/.wp-env.json
+++ b/.wp-env.json
@@ -1,7 +1,7 @@
 {
 	"plugins": [
 		".",
-		"https://downloads.wordpress.org/plugin/gutenberg.latest-stable.zip"
+		"https://github.com/WordPress/gutenberg/releases/download/v15.3.0-rc.2/gutenberg.zip"
 	],
 	"config": {
 		"SCRIPT_DEBUG": true

From 9d7b1e13d47972e3322b37024b1616d6a31c6fcb Mon Sep 17 00:00:00 2001
From: Bernie Reiter <ockham@raz.or.at>
Date: Thu, 9 Mar 2023 09:22:23 +0100
Subject: [PATCH 07/20] Revert "TEMP: Use GB v15.3.0 RC2"

This reverts commit bbc790fcfe2c8da31ada4793333c2d15138d434f.
---
 .wp-env.json | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.wp-env.json b/.wp-env.json
index 47b4bbd9..f282f93d 100644
--- a/.wp-env.json
+++ b/.wp-env.json
@@ -1,7 +1,7 @@
 {
 	"plugins": [
 		".",
-		"https://github.com/WordPress/gutenberg/releases/download/v15.3.0-rc.2/gutenberg.zip"
+		"https://downloads.wordpress.org/plugin/gutenberg.latest-stable.zip"
 	],
 	"config": {
 		"SCRIPT_DEBUG": true

From 3964533e6ef8ff0225c0a3aac8799d1df8c27cc4 Mon Sep 17 00:00:00 2001
From: Bernie Reiter <ockham@raz.or.at>
Date: Thu, 9 Mar 2023 13:08:15 +0100
Subject: [PATCH 08/20] In {g|s}et_inner_html, return to original position

---
 src/directives/class-wp-directive-processor.php | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/directives/class-wp-directive-processor.php b/src/directives/class-wp-directive-processor.php
index 1a346efb..370fb969 100644
--- a/src/directives/class-wp-directive-processor.php
+++ b/src/directives/class-wp-directive-processor.php
@@ -66,6 +66,7 @@ public function get_inner_html() {
 		$start = $this->bookmarks['start']->end + 1;
 		$end   = $this->bookmarks['end']->start;
 
+		$this->seek( 'start' ); // Return to original position.
 		$this->release_bookmark( 'start' );
 		$this->release_bookmark( 'end' );
 
@@ -83,6 +84,7 @@ public function set_inner_html( $new_html ) {
 		$start = $this->bookmarks['start']->end + 1;
 		$end   = $this->bookmarks['end']->start;
 
+		$this->seek( 'start' ); // Return to original position.
 		$this->release_bookmark( 'start' );
 		$this->release_bookmark( 'end' );
 

From a32cfa53c29bd1cda98b5cfd79c15308765ec05b Mon Sep 17 00:00:00 2001
From: Bernie Reiter <ockham@raz.or.at>
Date: Thu, 9 Mar 2023 13:11:24 +0100
Subject: [PATCH 09/20] Run get_updated_html in set_inner_html

---
 src/directives/class-wp-directive-processor.php | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/directives/class-wp-directive-processor.php b/src/directives/class-wp-directive-processor.php
index 370fb969..08598aba 100644
--- a/src/directives/class-wp-directive-processor.php
+++ b/src/directives/class-wp-directive-processor.php
@@ -74,6 +74,8 @@ public function get_inner_html() {
 	}
 
 	public function set_inner_html( $new_html ) {
+		$this->get_updated_html(); // Apply potential previous updates.
+
 		$this->set_bookmark( 'start' );
 		if ( ! $this->next_balanced_closer() ) {
 			$this->release_bookmark( 'start' );

From 054c579f97d35414d975f683c3894c080b3045e0 Mon Sep 17 00:00:00 2001
From: Bernie Reiter <ockham@raz.or.at>
Date: Thu, 9 Mar 2023 13:28:40 +0100
Subject: [PATCH 10/20] Skip bookmark invalidation unit test

---
 phpunit/directives/wp-directive-processor.php | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/phpunit/directives/wp-directive-processor.php b/phpunit/directives/wp-directive-processor.php
index 8ca135de..b06e4430 100644
--- a/phpunit/directives/wp-directive-processor.php
+++ b/phpunit/directives/wp-directive-processor.php
@@ -99,6 +99,8 @@ public function test_set_inner_html_preceded_by_set_attribute_works() {
 	}
 
 	public function test_set_inner_html_invalidates_bookmarks_that_point_to_replaced_content() {
+		$this->markTestSkipped( "This requires on bookmark invalidation, which is only in GB's WP 6.3 compat layer." );
+
 		$tags = new WP_Directive_Processor( self::HTML );
 
 		$tags->next_tag( 'section' );

From fc850326aee928a7be9d5abbf9905cf808ec8511 Mon Sep 17 00:00:00 2001
From: Bernie Reiter <ockham@raz.or.at>
Date: Tue, 14 Mar 2023 12:14:59 +0100
Subject: [PATCH 11/20] Move is_html_void_element into WP_Directive_Processor

---
 .../class-wp-directive-processor.php          | 22 ++++++++++++++++
 src/directives/wp-process-directives.php      | 26 ++-----------------
 2 files changed, 24 insertions(+), 24 deletions(-)

diff --git a/src/directives/class-wp-directive-processor.php b/src/directives/class-wp-directive-processor.php
index 08598aba..279b3749 100644
--- a/src/directives/class-wp-directive-processor.php
+++ b/src/directives/class-wp-directive-processor.php
@@ -93,4 +93,26 @@ public function set_inner_html( $new_html ) {
 		$this->lexical_updates[] = new WP_HTML_Text_Replacement( $start, $end, $new_html );
 		return true;
 	}
+
+	public static function is_html_void_element( $tag_name ) {
+		switch ( $tag_name ) {
+			case 'AREA':
+			case 'BASE':
+			case 'BR':
+			case 'COL':
+			case 'EMBED':
+			case 'HR':
+			case 'IMG':
+			case 'INPUT':
+			case 'LINK':
+			case 'META':
+			case 'SOURCE':
+			case 'TRACK':
+			case 'WBR':
+				return true;
+
+			default:
+				return false;
+		}
+	}
 }
\ No newline at end of file
diff --git a/src/directives/wp-process-directives.php b/src/directives/wp-process-directives.php
index c465d6ba..21ca430a 100644
--- a/src/directives/wp-process-directives.php
+++ b/src/directives/wp-process-directives.php
@@ -1,6 +1,7 @@
 <?php
 
 require_once __DIR__ . '/class-wp-directive-context.php';
+require_once __DIR__ . '/class-wp-directive-processor.php';
 
 function wp_process_directives( $tags, $prefix, $directives ) {
 	$context = new WP_Directive_Context;
@@ -41,7 +42,7 @@ function wp_process_directives( $tags, $prefix, $directives ) {
 			// directives so we can call its directive processor once we encounter the
 			// matching closing tag.
 			if (
-				! is_html_void_element( $tags->get_tag() ) &&
+				! WP_Directive_Processor::is_html_void_element( $tags->get_tag() ) &&
 				( 0 !== count( $attributes ) || 0 !== count( $tag_stack ) )
 			) {
 				$tag_stack[] = array( $tag_name, $attributes );
@@ -56,26 +57,3 @@ function wp_process_directives( $tags, $prefix, $directives ) {
 	return $tags;
 }
 
-// TODO: Move into `WP_HTML_Tag_Processor` (or `WP_HTML_Processor`).
-// See e.g. https://github.com/WordPress/gutenberg/pull/47573.
-function is_html_void_element( $tag_name ) {
-	switch ( $tag_name ) {
-		case 'AREA':
-		case 'BASE':
-		case 'BR':
-		case 'COL':
-		case 'EMBED':
-		case 'HR':
-		case 'IMG':
-		case 'INPUT':
-		case 'LINK':
-		case 'META':
-		case 'SOURCE':
-		case 'TRACK':
-		case 'WBR':
-			return true;
-
-		default:
-			return false;
-	}
-}

From 1a23ad9c558cdfb031868d2274aa49457fa8e66e Mon Sep 17 00:00:00 2001
From: Bernie Reiter <ockham@raz.or.at>
Date: Tue, 14 Mar 2023 12:15:19 +0100
Subject: [PATCH 12/20] Handle void elements in next_balanced_closer

---
 phpunit/directives/wp-directive-processor.php   | 9 +++++++++
 src/directives/class-wp-directive-processor.php | 5 +++++
 2 files changed, 14 insertions(+)

diff --git a/phpunit/directives/wp-directive-processor.php b/phpunit/directives/wp-directive-processor.php
index b06e4430..563daf82 100644
--- a/phpunit/directives/wp-directive-processor.php
+++ b/phpunit/directives/wp-directive-processor.php
@@ -12,6 +12,15 @@
 class WP_Directive_Processor_Test extends WP_UnitTestCase {
 	const HTML = '<div>outside</div><section><div><img>inside</div></section>';
 
+	public function test_next_balanced_closer_stays_on_void_tag() {
+		$tags = new WP_Directive_Processor( self::HTML );
+
+		$tags->next_tag( 'img' );
+		$result = $tags->next_balanced_closer();
+		$this->assertSame( 'IMG', $tags->get_tag() );
+		$this->assertFalse( $result );
+	}
+
 	public function test_next_balanced_closer_proceeds_to_correct_tag() {
 		$tags = new WP_Directive_Processor( self::HTML );
 
diff --git a/src/directives/class-wp-directive-processor.php b/src/directives/class-wp-directive-processor.php
index 279b3749..28ec9910 100644
--- a/src/directives/class-wp-directive-processor.php
+++ b/src/directives/class-wp-directive-processor.php
@@ -39,6 +39,11 @@ public function next_balanced_closer() {
 		$depth = 0;
 
 		$tag_name = $this->get_tag();
+
+		if ( self::is_html_void_element( $tag_name ) ) {
+			return false;
+		}
+
 		while ( $this->next_tag( array( 'tag_name' => $tag_name, 'tag_closers' => 'visit' ) ) ) {
 			if ( ! $this->is_tag_closer() ) {
 				$depth++;

From 351635ece27be4a8aa69f71bd7921902267cf8fa Mon Sep 17 00:00:00 2001
From: Bernie Reiter <ockham@raz.or.at>
Date: Tue, 14 Mar 2023 13:39:34 +0100
Subject: [PATCH 13/20] Add PHPDoc

---
 .../class-wp-directive-processor.php          | 35 +++++++++++++++++++
 1 file changed, 35 insertions(+)

diff --git a/src/directives/class-wp-directive-processor.php b/src/directives/class-wp-directive-processor.php
index 28ec9910..da0e736d 100644
--- a/src/directives/class-wp-directive-processor.php
+++ b/src/directives/class-wp-directive-processor.php
@@ -35,6 +35,16 @@ public function next_directive() {
 		return false;
 	}
 
+	/**
+	 * Find the matching closing tag for an opening tag.
+	 *
+	 * When called while on an open tag, traverse the HTML until we find
+	 * the matching closing tag, respecting any in-between content, including
+	 * nested tags of the same name. Return false when called on a closing or
+	 * void tag, or if no matching closing tag was found.
+	 *
+	 * @return bool True if a matching closing tag was found.
+	 */
 	public function next_balanced_closer() {
 		$depth = 0;
 
@@ -60,6 +70,14 @@ public function next_balanced_closer() {
 		return false;
 	}
 
+	/**
+	 * Return the content between two balanced tags.
+	 *
+	 * When called on an opening tag, return the HTML content found between
+	 * that opening tag and its matching closing tag.
+	 *
+	 * @return string The content between the current opening and its matching closing tag.
+	 */
 	public function get_inner_html() {
 		$this->set_bookmark( 'start' );
 		if ( ! $this->next_balanced_closer() ) {
@@ -78,6 +96,15 @@ public function get_inner_html() {
 		return substr( $this->html, $start, $end - $start );
 	}
 
+	/**
+	 * Set the content between two balanced tags.
+	 *
+	 * When called on an opening tag, set the HTML content found between
+	 * that opening tag and its matching closing tag.
+	 *
+	 * @param string $new_html The string to replace the content between the matching tags with.
+	 * @return bool            Whether the content was successfully replaced.
+	 */
 	public function set_inner_html( $new_html ) {
 		$this->get_updated_html(); // Apply potential previous updates.
 
@@ -99,6 +126,14 @@ public function set_inner_html( $new_html ) {
 		return true;
 	}
 
+	/**
+	 * Whether a given HTML element is void (e.g. <br>).
+	 *
+	 * @param string $tag_name The element in question.
+	 * @return bool True if the element is void.
+	 *
+	 * @see https://html.spec.whatwg.org/#elements-2
+	 */
 	public static function is_html_void_element( $tag_name ) {
 		switch ( $tag_name ) {
 			case 'AREA':

From 90ad44169420b1b0484bbc664d12b8e9a71eb3b7 Mon Sep 17 00:00:00 2001
From: Bernie Reiter <ockham@raz.or.at>
Date: Tue, 14 Mar 2023 13:47:00 +0100
Subject: [PATCH 14/20] Allow setting prefix

---
 src/directives/class-wp-directive-processor.php | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/src/directives/class-wp-directive-processor.php b/src/directives/class-wp-directive-processor.php
index da0e736d..69646e38 100644
--- a/src/directives/class-wp-directive-processor.php
+++ b/src/directives/class-wp-directive-processor.php
@@ -1,16 +1,18 @@
 <?php
 
 class WP_Directive_Processor extends WP_HTML_Tag_Processor {
-	const DIRECTIVE_PREFIX = 'WPX-';
-
 	public $html;
 
+	public $prefix;
+
 	public $might_have_directives = true;
 
-	public function __construct( $html ) {
+	public function __construct( $html, $prefix = 'wp-' ) {
 		parent::__construct( $html );
 
-		if ( false === stripos( self::DIRECTIVE_PREFIX, $html ) ) {
+		$this->prefix = $prefix;
+
+		if ( false === stripos( $this->prefix, $html ) ) {
 			$this->might_have_directives = false;
 		}
 	}
@@ -22,11 +24,11 @@ public function next_directive() {
 
 		while ( $this->next_tag( array( 'tag_closers' => 'visit' ) ) ) {
 			$tag_name = $this->get_tag();
-			if ( 0 === stripos( self::DIRECTIVE_PREFIX, $tag_name ) ) {
+			if ( 0 === stripos( $this->prefix, $tag_name ) ) {
 				return true;
 			}
 
-			$attribute_directives = $this->get_attribute_names_with_prefix( self::DIRECTIVE_PREFIX );
+			$attribute_directives = $this->get_attribute_names_with_prefix( $this->prefix );
 			if ( 0 < count( $attribute_directives ) ) {
 				return true;
 			}

From 05fcd77e90a2e436d2a1aaca8d52b1c53ba92ccd Mon Sep 17 00:00:00 2001
From: Bernie Reiter <ockham@raz.or.at>
Date: Tue, 14 Mar 2023 13:57:27 +0100
Subject: [PATCH 15/20] Needle <-> haystack

---
 src/directives/class-wp-directive-processor.php | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/directives/class-wp-directive-processor.php b/src/directives/class-wp-directive-processor.php
index 69646e38..3ce073cc 100644
--- a/src/directives/class-wp-directive-processor.php
+++ b/src/directives/class-wp-directive-processor.php
@@ -12,7 +12,7 @@ public function __construct( $html, $prefix = 'wp-' ) {
 
 		$this->prefix = $prefix;
 
-		if ( false === stripos( $this->prefix, $html ) ) {
+		if ( false === stripos( $html, $this->prefix ) ) {
 			$this->might_have_directives = false;
 		}
 	}
@@ -24,7 +24,7 @@ public function next_directive() {
 
 		while ( $this->next_tag( array( 'tag_closers' => 'visit' ) ) ) {
 			$tag_name = $this->get_tag();
-			if ( 0 === stripos( $this->prefix, $tag_name ) ) {
+			if ( 0 === stripos( $tag_name, $this->prefix ) ) {
 				return true;
 			}
 

From 749f11096c495716b5d436ed8d4d069d02b365ae Mon Sep 17 00:00:00 2001
From: Bernie Reiter <ockham@raz.or.at>
Date: Tue, 14 Mar 2023 14:00:27 +0100
Subject: [PATCH 16/20] Scrape directive specific stuff for now

---
 .../class-wp-directive-processor.php          | 36 -------------------
 1 file changed, 36 deletions(-)

diff --git a/src/directives/class-wp-directive-processor.php b/src/directives/class-wp-directive-processor.php
index 3ce073cc..5b9f091d 100644
--- a/src/directives/class-wp-directive-processor.php
+++ b/src/directives/class-wp-directive-processor.php
@@ -1,42 +1,6 @@
 <?php
 
 class WP_Directive_Processor extends WP_HTML_Tag_Processor {
-	public $html;
-
-	public $prefix;
-
-	public $might_have_directives = true;
-
-	public function __construct( $html, $prefix = 'wp-' ) {
-		parent::__construct( $html );
-
-		$this->prefix = $prefix;
-
-		if ( false === stripos( $html, $this->prefix ) ) {
-			$this->might_have_directives = false;
-		}
-	}
-
-	public function next_directive() {
-		if ( false === $this->might_have_directives ) {
-			return false;
-		}
-
-		while ( $this->next_tag( array( 'tag_closers' => 'visit' ) ) ) {
-			$tag_name = $this->get_tag();
-			if ( 0 === stripos( $tag_name, $this->prefix ) ) {
-				return true;
-			}
-
-			$attribute_directives = $this->get_attribute_names_with_prefix( $this->prefix );
-			if ( 0 < count( $attribute_directives ) ) {
-				return true;
-			}
-		}
-
-		return false;
-	}
-
 	/**
 	 * Find the matching closing tag for an opening tag.
 	 *

From 9b31d7b4069b5591258056f578f699566cd88058 Mon Sep 17 00:00:00 2001
From: Bernie Reiter <ockham@raz.or.at>
Date: Tue, 14 Mar 2023 14:26:46 +0100
Subject: [PATCH 17/20] set_inner_html: Make sure bookmarks don't collide

---
 .../class-wp-directive-processor.php          | 28 +++++++++++++------
 1 file changed, 20 insertions(+), 8 deletions(-)

diff --git a/src/directives/class-wp-directive-processor.php b/src/directives/class-wp-directive-processor.php
index 5b9f091d..4cbeecfe 100644
--- a/src/directives/class-wp-directive-processor.php
+++ b/src/directives/class-wp-directive-processor.php
@@ -74,19 +74,31 @@ public function get_inner_html() {
 	public function set_inner_html( $new_html ) {
 		$this->get_updated_html(); // Apply potential previous updates.
 
-		$this->set_bookmark( 'start' );
+		$i = 0;
+		while ( array_key_exists( 'start' . $i , $this->bookmarks ) ) {
+			++$i;
+		}
+		$start_name = 'start' . $i;
+
+		$this->set_bookmark( $start_name );
 		if ( ! $this->next_balanced_closer() ) {
-			$this->release_bookmark( 'start' );
+			$this->release_bookmark( $start_name );
 			return false;
 		}
-		$this->set_bookmark( 'end' );
 
-		$start = $this->bookmarks['start']->end + 1;
-		$end   = $this->bookmarks['end']->start;
+		$i = 0;
+		while ( array_key_exists( 'end' . $i , $this->bookmarks ) ) {
+			++$i;
+		}
+		$end_name = 'end' . $i;
+		$this->set_bookmark( $end_name );
 
-		$this->seek( 'start' ); // Return to original position.
-		$this->release_bookmark( 'start' );
-		$this->release_bookmark( 'end' );
+		$start = $this->bookmarks[ $start_name ]->end + 1;
+		$end   = $this->bookmarks[ $end_name ]->start;
+
+		$this->seek( $start_name ); // Return to original position.
+		$this->release_bookmark( $start_name );
+		$this->release_bookmark( $end_name );
 
 		$this->lexical_updates[] = new WP_HTML_Text_Replacement( $start, $end, $new_html );
 		return true;

From 0a163253477fc9d32a464e4666bc9015b0547508 Mon Sep 17 00:00:00 2001
From: Bernie Reiter <ockham@raz.or.at>
Date: Tue, 14 Mar 2023 14:29:52 +0100
Subject: [PATCH 18/20] Introduce get_balanced_bookmarks helper

---
 .../class-wp-directive-processor.php          | 33 ++++++++++++++-----
 1 file changed, 24 insertions(+), 9 deletions(-)

diff --git a/src/directives/class-wp-directive-processor.php b/src/directives/class-wp-directive-processor.php
index 4cbeecfe..9bab5829 100644
--- a/src/directives/class-wp-directive-processor.php
+++ b/src/directives/class-wp-directive-processor.php
@@ -74,6 +74,29 @@ public function get_inner_html() {
 	public function set_inner_html( $new_html ) {
 		$this->get_updated_html(); // Apply potential previous updates.
 
+		$bookmarks = $this->get_balanced_tag_bookmarks();
+		if ( ! $bookmarks ) {
+			return false;
+		}
+		list( $start_name, $end_name ) = $bookmarks;
+
+		$start = $this->bookmarks[ $start_name ]->end + 1;
+		$end   = $this->bookmarks[ $end_name ]->start;
+
+		$this->seek( $start_name ); // Return to original position.
+		$this->release_bookmark( $start_name );
+		$this->release_bookmark( $end_name );
+
+		$this->lexical_updates[] = new WP_HTML_Text_Replacement( $start, $end, $new_html );
+		return true;
+	}
+
+	/**
+	 * Return a pair of bookmarks for the current opening tag and the matching closing tag.
+	 *
+	 * @return array|false A pair of bookmarks, or false if there's no matching closing tag.
+	 */
+	public function get_balanced_tag_bookmarks() {
 		$i = 0;
 		while ( array_key_exists( 'start' . $i , $this->bookmarks ) ) {
 			++$i;
@@ -93,15 +116,7 @@ public function set_inner_html( $new_html ) {
 		$end_name = 'end' . $i;
 		$this->set_bookmark( $end_name );
 
-		$start = $this->bookmarks[ $start_name ]->end + 1;
-		$end   = $this->bookmarks[ $end_name ]->start;
-
-		$this->seek( $start_name ); // Return to original position.
-		$this->release_bookmark( $start_name );
-		$this->release_bookmark( $end_name );
-
-		$this->lexical_updates[] = new WP_HTML_Text_Replacement( $start, $end, $new_html );
-		return true;
+		return array( $start_name, $end_name );
 	}
 
 	/**

From c738c55d5d82a5fbe59c5f9d1e8421ddaed968c6 Mon Sep 17 00:00:00 2001
From: Bernie Reiter <ockham@raz.or.at>
Date: Tue, 14 Mar 2023 14:31:11 +0100
Subject: [PATCH 19/20] Use get_balanced_tag_bookmarks helper in
 get_inner_html()

---
 src/directives/class-wp-directive-processor.php | 17 ++++++++---------
 1 file changed, 8 insertions(+), 9 deletions(-)

diff --git a/src/directives/class-wp-directive-processor.php b/src/directives/class-wp-directive-processor.php
index 9bab5829..547fe61b 100644
--- a/src/directives/class-wp-directive-processor.php
+++ b/src/directives/class-wp-directive-processor.php
@@ -45,19 +45,18 @@ public function next_balanced_closer() {
 	 * @return string The content between the current opening and its matching closing tag.
 	 */
 	public function get_inner_html() {
-		$this->set_bookmark( 'start' );
-		if ( ! $this->next_balanced_closer() ) {
-			$this->release_bookmark( 'start' );
+		$bookmarks = $this->get_balanced_tag_bookmarks();
+		if ( ! $bookmarks ) {
 			return false;
 		}
-		$this->set_bookmark( 'end' );
+		list( $start_name, $end_name ) = $bookmarks;
 
-		$start = $this->bookmarks['start']->end + 1;
-		$end   = $this->bookmarks['end']->start;
+		$start = $this->bookmarks[ $start_name ]->end + 1;
+		$end   = $this->bookmarks[ $end_name ]->start;
 
-		$this->seek( 'start' ); // Return to original position.
-		$this->release_bookmark( 'start' );
-		$this->release_bookmark( 'end' );
+		$this->seek( $start_name ); // Return to original position.
+		$this->release_bookmark( $start_name );
+		$this->release_bookmark( $end_name );
 
 		return substr( $this->html, $start, $end - $start );
 	}

From eecd268135dcee100c23022d5d50d32235ec9c56 Mon Sep 17 00:00:00 2001
From: Bernie Reiter <ockham@raz.or.at>
Date: Tue, 14 Mar 2023 14:33:33 +0100
Subject: [PATCH 20/20] Format

---
 phpunit/directives/wp-directive-processor.php   |  2 +-
 src/directives/class-wp-directive-processor.php | 13 +++++++++----
 2 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/phpunit/directives/wp-directive-processor.php b/phpunit/directives/wp-directive-processor.php
index 563daf82..e24e247c 100644
--- a/phpunit/directives/wp-directive-processor.php
+++ b/phpunit/directives/wp-directive-processor.php
@@ -30,7 +30,7 @@ public function test_next_balanced_closer_proceeds_to_correct_tag() {
 		$this->assertTrue( $tags->is_tag_closer() );
 	}
 
-    public function test_next_balanced_closer_proceeds_to_correct_tag_for_nested_tag() {
+	public function test_next_balanced_closer_proceeds_to_correct_tag_for_nested_tag() {
 		$tags = new WP_Directive_Processor( self::HTML );
 
 		$tags->next_tag( 'div' );
diff --git a/src/directives/class-wp-directive-processor.php b/src/directives/class-wp-directive-processor.php
index 547fe61b..d9a18cf0 100644
--- a/src/directives/class-wp-directive-processor.php
+++ b/src/directives/class-wp-directive-processor.php
@@ -20,7 +20,12 @@ public function next_balanced_closer() {
 			return false;
 		}
 
-		while ( $this->next_tag( array( 'tag_name' => $tag_name, 'tag_closers' => 'visit' ) ) ) {
+		while ( $this->next_tag(
+			array(
+				'tag_name'    => $tag_name,
+				'tag_closers' => 'visit',
+			)
+		) ) {
 			if ( ! $this->is_tag_closer() ) {
 				$depth++;
 				continue;
@@ -97,7 +102,7 @@ public function set_inner_html( $new_html ) {
 	 */
 	public function get_balanced_tag_bookmarks() {
 		$i = 0;
-		while ( array_key_exists( 'start' . $i , $this->bookmarks ) ) {
+		while ( array_key_exists( 'start' . $i, $this->bookmarks ) ) {
 			++$i;
 		}
 		$start_name = 'start' . $i;
@@ -109,7 +114,7 @@ public function get_balanced_tag_bookmarks() {
 		}
 
 		$i = 0;
-		while ( array_key_exists( 'end' . $i , $this->bookmarks ) ) {
+		while ( array_key_exists( 'end' . $i, $this->bookmarks ) ) {
 			++$i;
 		}
 		$end_name = 'end' . $i;
@@ -147,4 +152,4 @@ public static function is_html_void_element( $tag_name ) {
 				return false;
 		}
 	}
-}
\ No newline at end of file
+}