Comments: Only type cast a scalar $comment_id in `get_comment_autho…

…r_link()`.

This aims to resolve a fatal error when the incoming `$comment_id` is an instance of `WP_Comment` (or any object) without a `comment_ID` property defined, or if it's empty:
{{{
Object of class WP_Comment could not be converted to string
}}}

This commit mirrors the changes previously made for a similar code fragment in `get_comment_author()`.

Includes:
* Unit tests to demonstrate the fatal error and validate the fix.
* Changing the default value for a non-existent comment ID in `get_comment_author()` from an empty string to zero as a numeric string, for consistency with `get_comment_ID()`.

Follow-up to [52818], [55289], [58335], [58755].

Props narenin, mukesh27, iflairwebtechnologies, umeshsinghin, SergeyBiryukov.
Fixes #61715.

git-svn-id: https://develop.svn.wordpress.org/trunk@58809 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/comment-template.php

@@ -29,7 +29,7 @@ function get_comment_author( $comment_id = 0 ) {
 	} elseif ( is_scalar( $comment_id ) ) {
 		$comment_id = (string) $comment_id;
 	} else {
-		$comment_id = '';
+		$comment_id = '0';
 	}
 
 	if ( empty( $comment->comment_author ) ) {
@@ -233,7 +233,13 @@ function get_comment_author_email_link( $link_text = '', $before = '', $after =
 function get_comment_author_link( $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 = '0';
+	}
 
 	$comment_author_url = get_comment_author_url( $comment );
 	$comment_author     = get_comment_author( $comment );

tests/phpunit/tests/comment/getCommentAuthorLink.php

@@ -0,0 +1,116 @@
+<?php
+
+/**
+ * @group comment
+ *
+ * @covers ::get_comment_author_link
+ */
+class Tests_Comment_GetCommentAuthorLink extends WP_UnitTestCase {
+
+	private static $comment;
+	private static $non_existent_comment_id;
+
+	public static function set_up_before_class() {
+		parent::set_up_before_class();
+
+		self::$comment = self::factory()->comment->create_and_get(
+			array(
+				'comment_post_ID' => 0,
+			)
+		);
+	}
+
+	public function get_comment_author_link_filter( $comment_author_link, $comment_author, $comment_id ) {
+		$this->assertSame( $comment_id, self::$comment->comment_ID, 'Comment IDs do not match.' );
+		$this->assertIsString( $comment_id, '$comment_id parameter is not a string.' );
+
+		return $comment_author_link;
+	}
+
+	public function test_comment_author_link_passes_correct_comment_id_for_comment_object() {
+		add_filter( 'get_comment_author_link', array( $this, 'get_comment_author_link_filter' ), 99, 3 );
+
+		get_comment_author_link( self::$comment );
+	}
+
+	public function test_comment_author_link_passes_correct_comment_id_for_int() {
+		add_filter( 'get_comment_author_link', array( $this, 'get_comment_author_link_filter' ), 99, 3 );
+
+		get_comment_author_link( (int) self::$comment->comment_ID );
+	}
+
+	public function get_comment_author_link_filter_non_existent_id( $comment_author_link, $comment_author, $comment_id ) {
+		$this->assertSame( $comment_id, (string) self::$non_existent_comment_id, 'Comment IDs do not match.' );
+		$this->assertIsString( $comment_id, '$comment_id parameter is not a string.' );
+
+		return $comment_author_link;
+	}
+
+	/**
+	 * @ticket 60475
+	 */
+	public function test_comment_author_link_passes_correct_comment_id_for_non_existent_comment() {
+		add_filter( 'get_comment_author_link', array( $this, 'get_comment_author_link_filter_non_existent_id' ), 99, 3 );
+
+		self::$non_existent_comment_id = self::$comment->comment_ID + 1;
+
+		get_comment_author_link( self::$non_existent_comment_id ); // Non-existent comment ID.
+	}
+
+	/**
+	 * @ticket 61681
+	 * @ticket 61715
+	 *
+	 * @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_link( $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',
+				),
+			),
+		);
+	}
+}