From 55d155d64a50bc7b002344a6802c90698b0f5d0f Mon Sep 17 00:00:00 2001
From: Dennis Snell <dennis.snell@automattic.com>
Date: Tue, 3 Mar 2026 11:28:58 -0600
Subject: [PATCH] Block Processor: add get_attribute_replacement().

There are useful times to modify the JSON attributes within a block.
This change proposes a new method which performs serialization on a
set of new attributes, and returns an update description on how to
apply those attributes textually against a document to make the edit.

This returns a `WP_HTML_Text_Replacement` instance with the range of
bytes that should be replaced, as well as the serialized content of
the update.
---
 src/wp-includes/class-wp-block-processor.php | 47 ++++++++++++++++++++
 1 file changed, 47 insertions(+)

diff --git a/src/wp-includes/class-wp-block-processor.php b/src/wp-includes/class-wp-block-processor.php
index 7b20fbf85d3bf..3244b9d633d4f 100644
--- a/src/wp-includes/class-wp-block-processor.php
+++ b/src/wp-includes/class-wp-block-processor.php
@@ -1891,6 +1891,53 @@ public function allocate_and_return_parsed_attributes(): ?array {
 			: null;
 	}
 
+	/**
+	 * Returns an indicator for how to replace the attributes in the given block,
+	 * including byte offsets for the replacement and full serialization of attributes.
+	 *
+	 * @since {WP_VERSION}
+	 *
+	 * @param array|null $new_attributes Serialize these attributes into the block.
+	 * @return WP_HTML_Text_Replacement|null
+	 */
+	public function get_attribute_replacement( $new_attributes ): ?WP_HTML_Text_Replacement {
+		if ( self::MATCHED !== $this->state || ! in_array( $this->type, array( self::OPENER, self::CLOSER ), true ) ) {
+			return null;
+		}
+
+		if ( null === $new_attributes ) {
+			if ( 0 === $this->json_length ) {
+				return null;
+			}
+
+			$whitespace_length = strspn( $this->source_text, " \t\f\r\n", $this->json_at + $this->json_length + 1 );
+			return new WP_HTML_Text_Replacement(
+				$this->json_at,
+				$this->json_length + $whitespace_length,
+				''
+			);
+		}
+
+		$encoded_attributes = wp_json_encode( $new_attributes, JSON_UNESCAPED_SLASHES | JSON_UNESCAPED_UNICODE );
+		$encoded_attributes = strtr(
+			$encoded_attributes,
+			array(
+				'\\\\' => '\u005c',
+				'--'   => '\u002d\u002d',
+				'<'    => '\u003c',
+				'>'    => '\u003e',
+				'&'    => '\u0026',
+				'\\"'  => '\u0022',
+			)
+		);
+
+		return new WP_HTML_Text_Replacement(
+			$this->json_at,
+			$this->json_length,
+			$encoded_attributes
+		);
+	}
+
 	/**
 	 * Returns the span representing the currently-matched delimiter, if matched, otherwise `null`.
 	 *