From 5b046976cc6d2498398986a6d3b717c9754f558b Mon Sep 17 00:00:00 2001
From: Sergey Biryukov <sergeybiryukov.ru@gmail.com>
Date: Mon, 4 May 2020 10:42:07 +0000
Subject: [PATCH] Canonical: Redirect paged requests for a static page assigned
 as the "Posts page".

This avoids displaying duplicate content of the home page under different URLs with appended page numbers.

This change only affects the `<!--nextpage-->` pagination (`page` query variable) and not the regular multiple posts pagination (`paged` query variable).

The posts page does not support the `<!--nextpage-->` pagination, so requests for invalid page numbers should be redirected to the page permalink, applying the logic previously implemented for single posts or pages.

Follow-up to [34492], [47727].

Props jeremyfelt, sachit.tandukar, SergeyBiryukov.
Fixes #45337. See #40773, #28081, #11694.
Built from https://develop.svn.wordpress.org/trunk@47760


git-svn-id: http://core.svn.wordpress.org/trunk@47536 1a063a9b-81f0-0310-95a4-ce76da25c4cd
---
 wp-includes/canonical.php | 24 ++++++++++++++++--------
 wp-includes/class-wp.php  | 21 +++++++++++++--------
 wp-includes/version.php   |  2 +-
 3 files changed, 30 insertions(+), 17 deletions(-)

diff --git a/wp-includes/canonical.php b/wp-includes/canonical.php
index b97db55709..12f7e5e467 100644
--- a/wp-includes/canonical.php
+++ b/wp-includes/canonical.php
@@ -186,6 +186,22 @@ function redirect_canonical( $requested_url = null, $do_redirect = true ) {
 			);
 		}
 
+		// Strip off non-existing <!--nextpage--> links from single posts or pages.
+		if ( get_query_var( 'page' ) ) {
+			$post_id = 0;
+
+			if ( $wp_query->queried_object instanceof WP_Post ) {
+				$post_id = $wp_query->queried_object->ID;
+			} elseif ( $wp_query->post ) {
+				$post_id = $wp_query->post->ID;
+			}
+
+			$redirect_url = get_permalink( $post_id );
+
+			$redirect['path']  = rtrim( $redirect['path'], (int) get_query_var( 'page' ) . '/' );
+			$redirect['query'] = remove_query_arg( 'page', $redirect['query'] );
+		}
+
 		if ( ! $redirect_url ) {
 			$redirect_url = redirect_guess_404_permalink();
 
@@ -197,14 +213,6 @@ function redirect_canonical( $requested_url = null, $do_redirect = true ) {
 				);
 			}
 		}
-
-		// Strip off non-existing page links from single posts or pages.
-		if ( get_query_var( 'page' ) && $wp_query->post ) {
-			$redirect['path']  = rtrim( $redirect['path'], (int) get_query_var( 'page' ) . '/' );
-			$redirect['query'] = remove_query_arg( 'page', $redirect['query'] );
-
-			$redirect_url = get_permalink( $wp_query->post->ID );
-		}
 	} elseif ( is_object( $wp_rewrite ) && $wp_rewrite->using_permalinks() ) {
 
 		// Rewriting of old ?p=X, ?m=2004, ?m=200401, ?m=20040101.
diff --git a/wp-includes/class-wp.php b/wp-includes/class-wp.php
index 980777bb67..ba1f15d033 100644
--- a/wp-includes/class-wp.php
+++ b/wp-includes/class-wp.php
@@ -670,15 +670,15 @@ class WP {
 		} elseif ( $wp_query->posts ) {
 			$content_found = true;
 
-			$post = isset( $wp_query->post ) ? $wp_query->post : null;
-
-			// Only set X-Pingback for single posts that allow pings.
-			if ( is_singular() && $post && pings_open( $post ) && ! headers_sent() ) {
-				header( 'X-Pingback: ' . get_bloginfo( 'pingback_url', 'display' ) );
-			}
-
-			// Check for paged content that exceeds the max number of pages.
 			if ( is_singular() ) {
+				$post = isset( $wp_query->post ) ? $wp_query->post : null;
+
+				// Only set X-Pingback for single posts that allow pings.
+				if ( $post && pings_open( $post ) && ! headers_sent() ) {
+					header( 'X-Pingback: ' . get_bloginfo( 'pingback_url', 'display' ) );
+				}
+
+				// Check for paged content that exceeds the max number of pages.
 				$next = '<!--nextpage-->';
 				if ( $post && ! empty( $this->query_vars['page'] ) ) {
 					// Check if content is actually intended to be paged.
@@ -691,6 +691,11 @@ class WP {
 				}
 			}
 
+			// The posts page does not support the <!--nextpage--> pagination.
+			if ( $wp_query->is_posts_page && ! empty( $this->query_vars['page'] ) ) {
+				$content_found = false;
+			}
+
 			if ( $content_found ) {
 				$set_404 = false;
 			}
diff --git a/wp-includes/version.php b/wp-includes/version.php
index 8bc17e3e57..661db90b0b 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.5-alpha-47759';
+$wp_version = '5.5-alpha-47760';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.