toJSON() in IDL doesn't serialize attributes from child interfaces but should: - https://webidl.spec.whatwg.org/#es-default-tojson This is causing issues with ReportBody / CSPViolationReportBody / TestReportBody.
Example: ReportBody's toJSON(), when marked as [Default] as per spec, when called on CSPViolationReportBody should return the same result as CSPViolationReportBody's toJSON(), with all the CSP values. However, since CSPViolationReportBody and other subclasses now have own toJSON() methods (https://github.com/w3c/webappsec-csp/issues/546), this issue isn't the high priority to fix.
<rdar://problem/99937603>