An opaque origin has to serialize as "null". It appears this doesn't happen in Safari: https://github.com/web-platform-tests/wpt/pull/31305. Noticed this while refactoring the specification to do away with cannot-be-a-base-URL in favor of a type: https://github.com/whatwg/url/pull/655.
Created attachment 441747 [details] Patch
This patch modifies the imported WPT tests. Please ensure that any changes on the tests (not coming from a WPT import) are exported to WPT. Please see https://trac.webkit.org/wiki/WPTExportProcess
Thanks, Anne!
Committed r284478 (243237@main): <https://commits.webkit.org/243237@main> All reviewed patches have been landed. Closing bug and clearing flags on attachment 441747 [details].
<rdar://problem/84427378>
Committed r284483 (243241@main): <https://commits.webkit.org/243241@main>