From 65e39deeec79fba1ef3613398fe3cb93048f3a91 Mon Sep 17 00:00:00 2001
From: Bernie Reiter <bernhard-reiter@git.wordpress.org>
Date: Wed, 1 Nov 2023 12:44:02 +0000
Subject: [PATCH] Blocks: During traversal, allow post callback to modify
 block.

Both the `$pre_callback` and `$post_callback` functions that are given as arguments to `traverse_and_serialize_block(s)` receive a reference to the current block as their first argument. However, while any changes that the "pre" callback makes to the block are reflected by the serialized markup, the same wasn't true for the "post" callback: Any changes that it made were only applied ''after'' the block had already been serialized.

This commit changes the behavior such that `$post_callback`'s changes to the current block are also reflected in the serialized markup.

Reviewed by hellofromTonya.
Merges [56970] to the 6.4 branch.

See #59646.
Props gziolo.
Fixes #59669.

git-svn-id: https://develop.svn.wordpress.org/branches/6.4@57043 602fd350-edb4-49c9-b593-d223f7449a82
---
 src/wp-includes/blocks.php               | 15 +++++++++------
 tests/phpunit/tests/blocks/serialize.php | 17 +++++++++++++++++
 2 files changed, 26 insertions(+), 6 deletions(-)

diff --git a/src/wp-includes/blocks.php b/src/wp-includes/blocks.php
index b8baf87b35..74b20fae90 100644
--- a/src/wp-includes/blocks.php
+++ b/src/wp-includes/blocks.php
@@ -1063,18 +1063,20 @@ function traverse_and_serialize_block( $block, $pre_callback = null, $post_callb
 				);
 			}
 
-			$block_content .= traverse_and_serialize_block( $inner_block, $pre_callback, $post_callback );
-
 			if ( is_callable( $post_callback ) ) {
 				$next = count( $block['innerBlocks'] ) - 1 === $block_index
 					? null
 					: $block['innerBlocks'][ $block_index + 1 ];
 
-				$block_content .= call_user_func_array(
+				$post_markup = call_user_func_array(
 					$post_callback,
 					array( &$inner_block, &$block, $next )
 				);
 			}
+
+			$block_content .= traverse_and_serialize_block( $inner_block, $pre_callback, $post_callback );
+			$block_content .= isset( $post_markup ) ? $post_markup : '';
+
 			++$block_index;
 		}
 	}
@@ -1138,18 +1140,19 @@ function traverse_and_serialize_blocks( $blocks, $pre_callback = null, $post_cal
 			);
 		}
 
-		$result .= traverse_and_serialize_block( $block, $pre_callback, $post_callback );
-
 		if ( is_callable( $post_callback ) ) {
 			$next = count( $blocks ) - 1 === $index
 				? null
 				: $blocks[ $index + 1 ];
 
-			$result .= call_user_func_array(
+			$post_markup = call_user_func_array(
 				$post_callback,
 				array( &$block, &$parent_block, $next )
 			);
 		}
+
+		$result .= traverse_and_serialize_block( $block, $pre_callback, $post_callback );
+		$result .= isset( $post_markup ) ? $post_markup : '';
 	}
 
 	return $result;
diff --git a/tests/phpunit/tests/blocks/serialize.php b/tests/phpunit/tests/blocks/serialize.php
index 12da03e3cd..b4221ef3c5 100644
--- a/tests/phpunit/tests/blocks/serialize.php
+++ b/tests/phpunit/tests/blocks/serialize.php
@@ -74,6 +74,23 @@ class Tests_Blocks_Serialize extends WP_UnitTestCase {
 		);
 	}
 
+	/**
+	 * @ticket 59669
+	 *
+	 * @covers ::traverse_and_serialize_blocks
+	 */
+	public function test_traverse_and_serialize_blocks_post_callback_modifies_current_block() {
+		$markup = "<!-- wp:outer --><!-- wp:inner {\"key\":\"value\"} -->Example.<!-- /wp:inner -->\n\nExample.\n\n<!-- wp:void /--><!-- /wp:outer -->";
+		$blocks = parse_blocks( $markup );
+
+		$actual = traverse_and_serialize_blocks( $blocks, null, array( __CLASS__, 'add_attribute_to_inner_block' ) );
+
+		$this->assertSame(
+			"<!-- wp:outer --><!-- wp:inner {\"key\":\"value\",\"myattr\":\"myvalue\"} -->Example.<!-- /wp:inner -->\n\nExample.\n\n<!-- wp:void /--><!-- /wp:outer -->",
+			$actual
+		);
+	}
+
 	public static function add_attribute_to_inner_block( &$block ) {
 		if ( 'core/inner' === $block['blockName'] ) {
 			$block['attrs']['myattr'] = 'myvalue';