From 2d73050edae758b19154089b52890df91df6afdf Mon Sep 17 00:00:00 2001
From: Sergey Biryukov <sergeybiryukov@git.wordpress.org>
Date: Wed, 19 Feb 2020 03:50:38 +0000
Subject: [PATCH] Posts, Post Types: Discard `tags_input` parameter in
 `wp_update_post()` if it's the same as existing post tags.

This ensures that `wp_update_post()` does not unintentionally modify post tags if the post has several tags with the same name but different slugs.

Tags should only be modified if `tags_input` parameter was explicitly provided, and is different from the existing tags.

Props kaggdesign, SergeyBiryukov.
Fixes #45121.

git-svn-id: https://develop.svn.wordpress.org/trunk@47317 602fd350-edb4-49c9-b593-d223f7449a82
---
 src/wp-includes/post.php     | 14 +++++++++++
 tests/phpunit/tests/post.php | 49 +++++++++++++++++++++++++++++++++---
 2 files changed, 59 insertions(+), 4 deletions(-)

diff --git a/src/wp-includes/post.php b/src/wp-includes/post.php
index 48fe341655..df2c3b545d 100644
--- a/src/wp-includes/post.php
+++ b/src/wp-includes/post.php
@@ -4217,6 +4217,20 @@ function wp_update_post( $postarr = array(), $wp_error = false ) {
 		return wp_insert_attachment( $postarr, false, 0, $wp_error );
 	}
 
+	// Discard 'tags_input' parameter if it's the same as existing post tags.
+	if ( isset( $postarr['tags_input'] ) && is_object_in_taxonomy( $postarr['post_type'], 'post_tag' ) ) {
+		$tags      = get_the_terms( $postarr['ID'], 'post_tag' );
+		$tag_names = array();
+
+		if ( $tags && ! is_wp_error( $tags ) ) {
+			$tag_names = wp_list_pluck( $tags, 'name' );
+		}
+
+		if ( $postarr['tags_input'] === $tag_names ) {
+			unset( $postarr['tags_input'] );
+		}
+	}
+
 	return wp_insert_post( $postarr, $wp_error );
 }
 
diff --git a/tests/phpunit/tests/post.php b/tests/phpunit/tests/post.php
index 72a08691e6..d4672212cc 100644
--- a/tests/phpunit/tests/post.php
+++ b/tests/phpunit/tests/post.php
@@ -1118,8 +1118,8 @@ class Tests_Post extends WP_UnitTestCase {
 	}
 
 	/**
-	 * If a post is sticky and is updated by a user that does not have the publish_post capability, it should _stay_
-	 * sticky.
+	 * If a post is sticky and is updated by a user that does not have the publish_post capability,
+	 * it should _stay_ sticky.
 	 *
 	 * @ticket 24153
 	 */
@@ -1156,8 +1156,8 @@ class Tests_Post extends WP_UnitTestCase {
 	}
 
 	/**
-	 * If the `edit_post()` method is invoked by a user without publish_posts permission, the sticky status of the post
-	 * should not be changed.
+	 * If the `edit_post()` method is invoked by a user without publish_posts permission,
+	 * the sticky status of the post should not be changed.
 	 *
 	 * @ticket 24153
 	 */
@@ -1426,4 +1426,45 @@ class Tests_Post extends WP_UnitTestCase {
 		$post = get_post( $post_id );
 		self::assertEquals( strtotime( gmdate( 'Y-m-d H:i:s' ) ), strtotime( $post->post_date_gmt ), 'The dates should be equal', 2 );
 	}
+
+	/**
+	 * Test ensuring that wp_update_post() does not unintentionally modify post tags
+	 * if the post has several tags with the same name but different slugs.
+	 *
+	 * Tags should only be modified if 'tags_input' parameter was explicitly provided,
+	 * and is different from the existing tags.
+	 *
+	 * @ticket 45121
+	 */
+	public function test_update_post_should_only_modify_post_tags_if_different_tags_input_was_provided() {
+		$tag_1 = wp_insert_term( 'wp_update_post_tag', 'post_tag', array( 'slug' => 'wp_update_post_tag_1' ) );
+		$tag_2 = wp_insert_term( 'wp_update_post_tag', 'post_tag', array( 'slug' => 'wp_update_post_tag_2' ) );
+		$tag_3 = wp_insert_term( 'wp_update_post_tag', 'post_tag', array( 'slug' => 'wp_update_post_tag_3' ) );
+
+		$post_id = self::factory()->post->create(
+			array(
+				'tags_input' => array( $tag_1['term_id'], $tag_2['term_id'] ),
+			)
+		);
+
+		$post = get_post( $post_id );
+
+		$tags = wp_get_post_tags( $post->ID, array( 'fields' => 'ids' ) );
+		$this->assertEqualSets( array( $tag_1['term_id'], $tag_2['term_id'] ), $tags );
+
+		wp_update_post( $post );
+
+		$tags = wp_get_post_tags( $post->ID, array( 'fields' => 'ids' ) );
+		$this->assertEqualSets( array( $tag_1['term_id'], $tag_2['term_id'] ), $tags );
+
+		wp_update_post(
+			array(
+				'ID'         => $post->ID,
+				'tags_input' => array( $tag_2['term_id'], $tag_3['term_id'] ),
+			)
+		);
+
+		$tags = wp_get_post_tags( $post->ID, array( 'fields' => 'ids' ) );
+		$this->assertEqualSets( array( $tag_2['term_id'], $tag_3['term_id'] ), $tags );
+	}
 }