From 5bc27525241d425fed20ebf67ca7b84205b8cb43 Mon Sep 17 00:00:00 2001
From: Jake Spurlock <whyisjake@git.wordpress.org>
Date: Thu, 23 Sep 2021 20:26:28 +0000
Subject: [PATCH] Posts, Post Types: Don't add a trailing number when there is
 a unique post parent.

WordPress tries to avoid an issue where slugs might match an existing slug of a page/post.
If we are in a hierarchical post type, there will be a level, and we can leave it the same.

Props stormrockwell, SergeyBiryukov, terriann, tubys, jeremyfelt, Daschmi, MaximeCulea, knutsp, whyisjake.
Fixes #51147.
See also #44112 and #45260.


git-svn-id: https://develop.svn.wordpress.org/trunk@51855 602fd350-edb4-49c9-b593-d223f7449a82
---
 src/wp-admin/includes/ms.php                  |  3 +
 .../tests/multisite/msPermalinkCollision.php  | 82 +++++++++++++++++++
 2 files changed, 85 insertions(+)
 create mode 100644 tests/phpunit/tests/multisite/msPermalinkCollision.php

diff --git a/src/wp-admin/includes/ms.php b/src/wp-admin/includes/ms.php
index 7796745a2e..76af47f8af 100644
--- a/src/wp-admin/includes/ms.php
+++ b/src/wp-admin/includes/ms.php
@@ -736,6 +736,9 @@ function avoid_blog_page_permalink_collision( $data, $postarr ) {
 	if ( ! is_main_site() ) {
 		return $data;
 	}
+	if ( isset( $data['post_parent'] ) && $data['post_parent'] ) {
+		return $data;
+	}
 
 	$post_name = $data['post_name'];
 	$c         = 0;
diff --git a/tests/phpunit/tests/multisite/msPermalinkCollision.php b/tests/phpunit/tests/multisite/msPermalinkCollision.php
new file mode 100644
index 0000000000..1a8c25a75c
--- /dev/null
+++ b/tests/phpunit/tests/multisite/msPermalinkCollision.php
@@ -0,0 +1,82 @@
+<?php
+
+if ( is_multisite() ) :
+
+	/**
+	 * Tests specific to `avoid_blog_page_permalink_collision()` in multisite.
+	 *
+	 * @group multisite
+	 * @group only
+	 */
+	class Tests_Multisite_MS_Permalink_Collision extends WP_UnitTestCase {
+		protected $suppress = false;
+		protected static $site_id;
+		protected static $root_page;
+		protected static $child_page;
+		protected static $post_and_blog_path = 'permalink-collison';
+
+		/**
+		 * Create a blog and the pages we need to test the collision.
+		 */
+		public static function wpSetUpBeforeClass( $factory ) {
+			self::$site_id = self::factory()->blog->create(
+				array(
+					'path' => '/' . self::$post_and_blog_path,
+				)
+			);
+
+			self::$root_page = self::factory()->post->create_and_get(
+				array(
+					'post_type'   => 'page',
+					'post_title'  => 'Bar',
+					'post_name'   => self::$post_and_blog_path,
+				)
+			);
+
+			self::$child_page = self::factory()->post->create_and_get(
+				array(
+					'post_parent' => self::$root_page->ID,
+					'post_type'   => 'page',
+					'post_title'  => 'Bar',
+					'post_name'   => self::$post_and_blog_path,
+				)
+			);
+		}
+
+		public function setUp() {
+			global $wpdb;
+			parent::setUp();
+			$this->suppress = $wpdb->suppress_errors();
+		}
+
+		public function tearDown() {
+			global $wpdb;
+			$wpdb->suppress_errors( $this->suppress );
+			parent::tearDown();
+		}
+
+		/**
+		 * Delete blog and pages we created.
+		 */
+		public static function wpTearDownAfterClass() {
+			wp_delete_site( self::$site_id );
+
+			wp_delete_post( self::$root_page->ID );
+			wp_delete_post( self::$child_page->ID );
+		}
+
+		public function test_avoid_blog_page_permalink_collision_renames_post_name() {
+			$this->assertNotEquals( self::$post_and_blog_path, self::$root_page->post_name );
+		}
+
+		/**
+		 * Ensure `avoid_blog_page_permalink_collision()` doesn't rename child pages post_name.
+		 *
+		 * @ticket 51147
+		 */
+		public function test_avoid_blog_page_permalink_collision_doesnt_rename_child_pages() {
+			$this->assertEquals( self::$post_and_blog_path, self::$child_page->post_name );
+		}
+	}
+
+endif;