From 729bb10f31d67430b0efbf366c5c8bd2cb18c237 Mon Sep 17 00:00:00 2001
From: John Blackbourn <johnbillion@git.wordpress.org>
Date: Mon, 1 Feb 2021 21:20:44 +0000
Subject: [PATCH] Posts, Post Types: Introduce new functions for determining if
 a post has a parent (`has_post_parent()`) and to fetch the post parent
 (`get_post_parent()`).

These functions are simple but reduce the logic needed in themes and plugins.

Props ramiy, sebastian.pisula, birgire, audrasjb, xkon

Fixes #33045


git-svn-id: https://develop.svn.wordpress.org/trunk@50127 602fd350-edb4-49c9-b593-d223f7449a82
---
 src/wp-includes/post-template.php     | 25 +++++++++++
 tests/phpunit/tests/post/template.php | 61 +++++++++++++++++++++++++++
 2 files changed, 86 insertions(+)

diff --git a/src/wp-includes/post-template.php b/src/wp-includes/post-template.php
index 0ad352c328..cdc2341c04 100644
--- a/src/wp-includes/post-template.php
+++ b/src/wp-includes/post-template.php
@@ -1963,3 +1963,28 @@ function wp_list_post_revisions( $post_id = 0, $type = 'all' ) {
 	echo $rows;
 	echo '</ul>';
 }
+
+/**
+ * Retrieves the parent post object for the given post.
+ *
+ * @since 5.7.0
+ *
+ * @param int|WP_Post|null $post Optional. Post ID or WP_Post object. Default is global $post.
+ * @return WP_Post|null Parent post object, or null if there isn't one.
+ */
+function get_parent_post( $post = null ) {
+	$wp_post = get_post( $post );
+	return ! empty( $wp_post->post_parent ) ? get_post( $wp_post->post_parent ) : null;
+}
+
+/**
+ * Returns whether the given post has a parent post.
+ *
+ * @since 5.7.0
+ *
+ * @param int|WP_Post|null $post Optional. Post ID or WP_Post object. Default is global $post.
+ * @return bool Whether the post has a parent post.
+ */
+function has_parent_post( $post = null ) {
+	return (bool) get_parent_post( $post );
+}
diff --git a/tests/phpunit/tests/post/template.php b/tests/phpunit/tests/post/template.php
index f1bcaebcf0..a9d3fc1704 100644
--- a/tests/phpunit/tests/post/template.php
+++ b/tests/phpunit/tests/post/template.php
@@ -452,4 +452,65 @@ NO;
 		$this->assertRegExp( '/><li.*>|<\/li></U', $menu );
 
 	}
+
+	/**
+	 * @ticket 33045
+	 */
+	public function test_get_parent_post() {
+		$post = array(
+			'post_status' => 'publish',
+			'post_type'   => 'page',
+		);
+
+		// Insert two initial posts.
+		$parent_id = self::factory()->post->create( $post );
+		$child_id  = self::factory()->post->create( $post );
+
+		// Test if child get_parent_post() post returns Null by default.
+		$parent = get_parent_post( $child_id );
+		$this->assertNull( $parent );
+
+		// Update child post with a parent.
+		wp_update_post(
+			array(
+				'ID'          => $child_id,
+				'post_parent' => $parent_id,
+			)
+		);
+
+		// Test if child get_parent_post() post returns the parent object.
+		$parent = get_parent_post( $child_id );
+		$this->assertNotNull( $parent );
+		$this->assertSame( $parent_id, $parent->ID );
+	}
+
+	/**
+	 * @ticket 33045
+	 */
+	public function test_has_parent_post() {
+		$post = array(
+			'post_status' => 'publish',
+			'post_type'   => 'page',
+		);
+
+		// Insert two initial posts.
+		$parent_id = self::factory()->post->create( $post );
+		$child_id  = self::factory()->post->create( $post );
+
+		// Test if child has_parent_post() post returns False by default.
+		$parent = has_parent_post( $child_id );
+		$this->assertFalse( $parent );
+
+		// Update child post with a parent.
+		wp_update_post(
+			array(
+				'ID'          => $child_id,
+				'post_parent' => $parent_id,
+			)
+		);
+
+		// Test if child has_parent_post() returns True.
+		$parent = has_parent_post( $child_id );
+		$this->assertTrue( $parent );
+	}
 }