Comments: Fix fatal error when get_comment_author() receives an objec…

…t with no comment_id.

[58335] introduced `(string)` type casting of the passed in `$comment_id` value. If `$comment_id` is a scalar, it works as expected. But if it's an `object`, the following fatal error is thrown:

{{{
Object of class WP_Comment could not be converted to string
}}}

This fatal error happens when the incoming `$comment_id` is an instance of `WP_Comment` (or any object) without a `comment_ID` (empty). 

This changeset adds tests to demonstrate the fatal error and validate the fix.

It fixes the fatal error by restructuring the ternary checks into an `if/elseif/else` structure for the 3 paths:

- When `$comment->comment_ID` is not empty, then it uses the property.
- When `$comment_id` is scalar, then it type casts it to a `string`.
- Else, the default is an empty `string`.

Follow-up to [58335], [41127], [52818].

Props ambrosiawt, hellofromTonya, jorbin, mukesh27, SergeyBiryukov.
Fixes #61681.

git-svn-id: https://develop.svn.wordpress.org/trunk@58755 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/comment-template.php

@@ -24,7 +24,13 @@
 function get_comment_author( $comment_id = 0 ) {
 	$comment = get_comment( $comment_id );
 
-	$comment_id = ! empty( $comment->comment_ID ) ? $comment->comment_ID : (string) $comment_id;
+	if ( ! empty( $comment->comment_ID ) ) {
+		$comment_id = $comment->comment_ID;
+	} elseif ( is_scalar( $comment_id ) ) {
+		$comment_id = (string) $comment_id;
+	} else {
+		$comment_id = '';
+	}
 
 	if ( empty( $comment->comment_author ) ) {
 		$user = ! empty( $comment->user_id ) ? get_userdata( $comment->user_id ) : false;

tests/phpunit/tests/comment/getCommentAuthor.php

@@ -56,4 +56,58 @@ public function test_comment_author_passes_correct_comment_id_for_non_existent_c
 
 		get_comment_author( self::$non_existent_comment_id ); // Non-existent comment ID.
 	}
+
+	/**
+	 * @ticket 61681
+	 *
+	 * @dataProvider data_should_return_author_when_given_object_without_comment_id
+	 *
+	 * @param stdClass $comment_props Comment properties test data.
+	 * @param string   $expected      The expected result.
+	 * @param array    $user_data     Optional. User data for creating an author. Default empty array.
+	 */
+	public function test_should_return_author_when_given_object_without_comment_id( $comment_props, $expected, $user_data = array() ) {
+		if ( ! empty( $comment_props->user_id ) ) {
+			$user                   = self::factory()->user->create_and_get( $user_data );
+			$comment_props->user_id = $user->ID;
+		}
+		$comment = new WP_Comment( $comment_props );
+		$this->assertSame( $expected, get_comment_author( $comment ) );
+	}
+
+	/**
+	 * Data provider.
+	 *
+	 * @return array
+	 */
+	public function data_should_return_author_when_given_object_without_comment_id() {
+		return array(
+			'with no author'             => array(
+				'comment_props' => new stdClass(),
+				'expected'      => 'Anonymous',
+			),
+			'with author name'           => array(
+				'comment_props' => (object) array(
+					'comment_author' => 'tester1',
+				),
+				'expected'      => 'tester1',
+			),
+			'with author name, empty ID' => array(
+				'comment_props' => (object) array(
+					'comment_author' => 'tester2',
+					'comment_ID'     => '',
+				),
+				'expected'      => 'tester2',
+			),
+			'with author ID'             => array(
+				'comment_props' => (object) array(
+					'user_id' => 1, // populates in the test with an actual user ID.
+				),
+				'expected'      => 'Tester3',
+				'user_data'     => array(
+					'display_name' => 'Tester3',
+				),
+			),
+		);
+	}
 }