Posts, Post Types: Update get_the_modified_author() to handle missing global $post and add (missing) $post arg.

The addition of the `$post` argument (which defaults to the global post) brings `get_the_modified_author()` in line with other similar functions, including `get_the_modified_date()` and `get_the_modified_time()`.  

Props Cornwell, jdahir0789, dhruvang21, Presskopp, mindctrl, samirmalpande, audrasjb, johnbillion, SergeyBiryukov, desrosj, costdev, mukesh27, westonruter.
Fixes #64104, #55978.


git-svn-id: https://develop.svn.wordpress.org/trunk@61057 602fd350-edb4-49c9-b593-d223f7449a82

Author: westonruter

src/wp-includes/author-template.php

@@ -86,24 +86,31 @@ function the_author( $deprecated = '', $deprecated_echo = true ) {
  * Retrieves the author who last edited the current post.
  *
  * @since 2.8.0
+ * @since 6.9.0 Added the `$post` parameter. Unknown return value is now explicitly null instead of void.
  *
- * @return string|void The author's display name, empty string if unknown.
+ * @param int|WP_Post|null $post Optional. Post ID or post object. Default is global `$post` object.
+ * @return string|null The author's display name. Empty string if user is unavailable. Null if there was no last editor or the post is invalid.
  */
-function get_the_modified_author() {
-	$last_id = get_post_meta( get_post()->ID, '_edit_last', true );
-
-	if ( $last_id ) {
-		$last_user = get_userdata( $last_id );
+function get_the_modified_author( $post = null ) {
+	$post = get_post( $post );
+	if ( ! $post ) {
+		return null;
+	}
 
-		/**
-		 * Filters the display name of the author who last edited the current post.
-		 *
-		 * @since 2.8.0
-		 *
-		 * @param string $display_name The author's display name, empty string if unknown.
-		 */
-		return apply_filters( 'the_modified_author', $last_user ? $last_user->display_name : '' );
+	$last_id = get_post_meta( $post->ID, '_edit_last', true );
+	if ( ! $last_id ) {
+		return null;
 	}
+	$last_user = get_userdata( $last_id );
+
+	/**
+	 * Filters the display name of the author who last edited the current post.
+	 *
+	 * @since 2.8.0
+	 *
+	 * @param string $display_name The author's display name, empty string if user is unavailable.
+	 */
+	return apply_filters( 'the_modified_author', $last_user ? $last_user->display_name : '' );
 }
 
 /**

tests/phpunit/tests/user/getTheModifiedAuthor.php

@@ -37,7 +37,7 @@ public static function wpSetUpBeforeClass( WP_UnitTest_Factory $factory ) {
 	public function set_up() {
 		parent::set_up();
 
-		$GLOBALS['post'] = self::$post_id;
+		$GLOBALS['post'] = get_post( self::$post_id );
 	}
 
 	public function test_get_the_modified_author() {
@@ -56,4 +56,44 @@ public function test_get_the_modified_author_should_return_empty_string_if_user_
 
 		$this->assertSame( '', get_the_modified_author() );
 	}
+
+	/**
+	 * @ticket 64104
+	 */
+	public function test_get_the_modified_author_when_post_global_does_not_exist() {
+		$GLOBALS['post'] = null;
+		$this->assertNull( get_the_modified_author() );
+	}
+
+	/**
+	 * @ticket 64104
+	 */
+	public function test_get_the_modified_author_when_invalid_post() {
+		$this->assertNull( get_the_modified_author( -1 ) );
+	}
+
+	/**
+	 * @ticket 64104
+	 */
+	public function test_get_the_modified_author_for_another_post() {
+		$expected_display_name = 'Test Editor';
+
+		$editor_id = self::factory()->user->create(
+			array(
+				'role'         => 'editor',
+				'user_login'   => 'test_editor',
+				'display_name' => $expected_display_name,
+				'description'  => 'test_editor',
+			)
+		);
+
+		$another_post_id = self::factory()->post->create();
+
+		$this->assertNull( get_the_modified_author( $another_post_id ) );
+		$this->assertNull( get_the_modified_author( get_post( $another_post_id ) ) );
+
+		add_post_meta( $another_post_id, '_edit_last', $editor_id );
+		$this->assertSame( $expected_display_name, get_the_modified_author( $another_post_id ) );
+		$this->assertSame( $expected_display_name, get_the_modified_author( get_post( $another_post_id ) ) );
+	}
 }