Tests: Add unit test for empty comment tags in export

src/wp-admin/includes/export.php

@@ -685,7 +685,12 @@ function wxr_filter_postmeta( $return_me, $meta_key ) {
 	endforeach;
 
 				$_comments = $wpdb->get_results( $wpdb->prepare( "SELECT * FROM $wpdb->comments WHERE comment_post_ID = %d AND comment_approved <> 'spam'", $post->ID ) );
-				$comments  = array_map( 'get_comment', $_comments );
+				$comments  = array_filter(
+					array_map( 'get_comment', $_comments ),
+					static function ( $comment ) {
+						return $comment instanceof WP_Comment;
+					}
+				);
 				foreach ( $comments as $c ) :
 					?>
 		<wp:comment>

src/wp-includes/comment.php

@@ -240,9 +240,12 @@ function get_comment( $comment = null, $output = OBJECT ) {
 	 *
 	 * @since 2.3.0
 	 *
-	 * @param WP_Comment $_comment Comment data.
+	 * @param WP_Comment|null $_comment Comment data.
 	 */
 	$_comment = apply_filters( 'get_comment', $_comment );
+	if ( ! ( $_comment instanceof WP_Comment ) ) {
+		return null;
+	}
 
 	if ( OBJECT === $output ) {
 		return $_comment;

tests/phpunit/tests/admin/exportWp.php

@@ -290,4 +290,37 @@ private function populate_args_post_authors( array &$args, $expected_ids ) {
 		$post_ids_key   = $expected_ids[0];
 		$args['author'] = self::$post_ids[ $post_ids_key ]['post_author'];
 	}
+
+	/**
+	 * @ticket 61244
+	 */
+	public function test_export_wp_should_not_include_empty_comments_when_filtered() {
+		$post_id = self::factory()->post->create( array( 'post_title' => 'Test Post' ) );
+		self::factory()->comment->create_post_comments( $post_id, 3 );
+
+		// Add filter to make get_comment return null.
+		add_action(
+			'export_wp',
+			static function () {
+				add_filter( 'get_comment', '__return_null' );
+			}
+		);
+
+		$xml_obj      = $this->get_the_export( array() );
+		$comment_tags = $xml_obj->xpath( '//wp:comment' );
+		$this->assertCount( 0, $comment_tags, 'No <wp:comment> tags should be present when comments are filtered out.' );
+	}
+
+	/**
+	 * @ticket 61244
+	 */
+	public function test_export_wp_includes_comments_when_not_filtered() {
+		$post_id       = self::factory()->post->create( array( 'post_title' => 'Test Post' ) );
+		$comment_count = 3;
+		self::factory()->comment->create_post_comments( $post_id, $comment_count );
+
+		$xml_obj      = $this->get_the_export( array() );
+		$comment_tags = $xml_obj->xpath( '//wp:comment' );
+		$this->assertCount( $comment_count, $comment_tags, 'Export should include all comments when not filtered.' );
+	}
 }

tests/phpunit/tests/comment.php

@@ -1896,4 +1896,20 @@ public function test_wp_trash_comment_only_top_level_notes_trigger_child_deletio
 		// Verify the sibling note is NOT trashed (no cascade since child is not top-level).
 		$this->assertSame( '1', get_comment( $sibling_note )->comment_approved );
 	}
+
+	/**
+	 * @ticket 61244
+	 *
+	 * @covers ::get_comment
+	 */
+	public function test_get_comment_filter() {
+		$comment_id = self::factory()->comment->create( array( 'comment_post_ID' => self::$post_id ) );
+
+		$comment = get_comment( $comment_id );
+		$this->assertInstanceOf( WP_Comment::class, $comment );
+		$this->assertSame( $comment_id, (int) $comment->comment_ID, 'Expected the same comment.' );
+
+		add_filter( 'get_comment', '__return_null' );
+		$this->assertNull( get_comment( $comment_id ), 'Expected get_comment() to return null when get_comment filter returns null.' );
+	}
 }