Posts, Post types: Prevent get_sample_permalink() modifying the post object.

`get_sample_permalink()` (ab)uses the `$post->filter` property to indicate a sample permalink is being generated for the post. This change ensures the property is restored to its original value.

Props herregroen, hellofromTonya, peterwilsoncc, Rahmohn, costdev.
Fixes #54736.




git-svn-id: https://develop.svn.wordpress.org/trunk@54244 602fd350-edb4-49c9-b593-d223f7449a82

Author: peterwilsoncc

src/wp-admin/includes/post.php

@@ -1399,6 +1399,7 @@ function get_sample_permalink( $post, $title = null, $name = null ) {
 	$original_status = $post->post_status;
 	$original_date   = $post->post_date;
 	$original_name   = $post->post_name;
+	$original_filter = $post->filter;
 
 	// Hack: get_permalink() would return plain permalink for drafts, so we will fake that our post is published.
 	if ( in_array( $post->post_status, array( 'draft', 'pending', 'future' ), true ) ) {
@@ -1443,7 +1444,7 @@ function get_sample_permalink( $post, $title = null, $name = null ) {
 	$post->post_status = $original_status;
 	$post->post_date   = $original_date;
 	$post->post_name   = $original_name;
-	unset( $post->filter );
+	$post->filter      = $original_filter;
 
 	/**
 	 * Filters the sample permalink.

tests/phpunit/tests/admin/includesPost.php

@@ -686,6 +686,36 @@ public function test_get_sample_permalink_should_respect_hierarchy_of_draft_page
 		$this->assertSame( 'child-page', $actual[1] );
 	}
 
+	/**
+	 * Tests that get_sample_permalink() preserves the original WP_Post properties.
+	 *
+	 * @ticket 54736
+	 *
+	 * @covers ::get_sample_permalink
+	 */
+	public function test_get_sample_permalink_should_preserve_the_original_post_properties() {
+		$post = self::factory()->post->create_and_get(
+			array(
+				'post_status' => 'draft',
+			)
+		);
+
+		$post_original = clone $post;
+
+		add_filter(
+			'get_sample_permalink',
+			function( $permalink, $post_id, $title, $name, $post ) use ( $post_original ) {
+				$this->assertEquals( $post_original, $post, 'Modified post object passed to get_sample_permalink filter.' );
+				return $permalink;
+			},
+			10,
+			5
+		);
+
+		get_sample_permalink( $post );
+		$this->assertEquals( $post_original, $post, 'get_sample_permalink() modifies the post object.' );
+	}
+
 	public function test_post_exists_should_match_title() {
 		$p = self::factory()->post->create(
 			array(