From 2e7faf2ae3641ccce58c148a0a2db0945bc01654 Mon Sep 17 00:00:00 2001
From: Bernie Reiter <ockham@raz.or.at>
Date: Tue, 3 May 2022 17:55:27 +0200
Subject: [PATCH] Comment Template: With pagination, make sure to request page
 1 if there are no comments (#40759)

Co-authored-by: Tonya Mork <hello@hellofromtonya.com>
---
 lib/compat/wordpress-6.0/blocks.php           |  5 +-
 ...ss-block-library-comment-template-test.php | 54 +++++++++++++++++++
 2 files changed, 58 insertions(+), 1 deletion(-)

diff --git a/lib/compat/wordpress-6.0/blocks.php b/lib/compat/wordpress-6.0/blocks.php
index 934a2fc8b87555..7a3f6b728eebc0 100644
--- a/lib/compat/wordpress-6.0/blocks.php
+++ b/lib/compat/wordpress-6.0/blocks.php
@@ -176,7 +176,10 @@ function build_comment_query_vars_from_block( $block ) {
 				} elseif ( 'oldest' === $default_page ) {
 					$comment_args['paged'] = 1;
 				} elseif ( 'newest' === $default_page ) {
-					$comment_args['paged'] = (int) ( new WP_Comment_Query( $comment_args ) )->max_num_pages;
+					$max_num_pages = (int) ( new WP_Comment_Query( $comment_args ) )->max_num_pages;
+					if ( 0 !== $max_num_pages ) {
+						$comment_args['paged'] = $max_num_pages;
+					}
 				}
 				// Set the `cpage` query var to ensure the previous and next pagination links are correct
 				// when inheriting the Discussion Settings.
diff --git a/phpunit/class-block-library-comment-template-test.php b/phpunit/class-block-library-comment-template-test.php
index c808ff5dc5c542..6e8a7ef0df311e 100644
--- a/phpunit/class-block-library-comment-template-test.php
+++ b/phpunit/class-block-library-comment-template-test.php
@@ -120,6 +120,60 @@ function test_build_comment_query_vars_from_block_no_context() {
 		);
 	}
 
+	/**
+	 * Test that if pagination is set to display the last page by default (i.e. newest comments),
+	 * the query is set to look for page 1 (rather than page 0, which would cause an error).
+	 *
+	 * Regression: https://github.com/WordPress/gutenberg/issues/40758.
+	 *
+	 * @covers ::build_comment_query_vars_from_block
+	 */
+	function test_build_comment_query_vars_from_block_pagination_with_no_comments() {
+		$comments_per_page     = get_option( 'comments_per_page' );
+		$default_comments_page = get_option( 'default_comments_page' );
+
+		update_option( 'comments_per_page', 50 );
+		update_option( 'previous_default_page', 'newest' );
+
+		$post_without_comments = self::factory()->post->create_and_get(
+			array(
+				'post_type'    => 'post',
+				'post_status'  => 'publish',
+				'post_name'    => 'fluffycat',
+				'post_title'   => 'Fluffy Cat',
+				'post_content' => 'Fluffy Cat content',
+				'post_excerpt' => 'Fluffy Cat',
+			)
+		);
+
+		$parsed_blocks = parse_blocks(
+			'<!-- wp:comment-template --><!-- wp:comment-author-name /--><!-- wp:comment-content /--><!-- /wp:comment-template -->'
+		);
+
+		$block = new WP_Block(
+			$parsed_blocks[0],
+			array(
+				'postId' => $post_without_comments->ID,
+			)
+		);
+
+		$this->assertEquals(
+			array(
+				'orderby'       => 'comment_date_gmt',
+				'order'         => 'ASC',
+				'status'        => 'approve',
+				'no_found_rows' => false,
+				'post_id'       => $post_without_comments->ID,
+				'hierarchical'  => 'threaded',
+				'number'        => 50,
+			),
+			build_comment_query_vars_from_block( $block )
+		);
+
+		update_option( 'comments_per_page', $comments_per_page );
+		update_option( 'default_comments_page', $default_comments_page );
+	}
+
 	/**
 	 * Test rendering a single comment
 	 */