[kunal649]

enhanceFetchErrorMessages already adds the host to generic fetch errors, so Failed to fetch becomes Failed to fetch (example.com). The catch is that it ran new URL(url) with no base, and that throws for relative URLs like /api/foo or the fetch("") from the issue. The try/catch swallowed the error, so those requests never got the host.

Now relative URLs are resolved against location.href instead of origin to safely handle sandboxed iframes and opaque origins without throwing. Absolute URLs ignore the base, and where there's no location (Node, workers) nothing changes. I also skip the enhancement when the resolved host is empty, like on file:// pages, otherwise you'd get Failed to fetch (). location is added to InternalGlobal for the typing.

Added 7 unit tests (relative URL, empty URL, no location, file:// origin, a relative path & an absolute URL in sandboxed srcdoc iframe , absolute URL on another origin).

This only touches the error message. The empty URL in the fetch breadcrumbs is a separate spot, so I left it out to discuss on the issue thread.

Ref #13168

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[s1gr1d]

Thank you so much for picking this up!

a small nit regarding the tests: they are all quite similar so you could use an it.each there, like this:

    it.each([
      ['a relative path', 'https://app.example.com/dashboard?tab=billing', '/api/users/42', 'Failed to fetch (app.example.com)'],
    ])('resolves %s against location.href', async (_name, href, target, expected) => {}

[s1gr1d]

Looks good now, thank you!

A few small things:

• Can you update the description so it mentions href?
• We should rename Fixes #13168 -> Ref #13168. This PR covers the fetch error message, but the issue also mentions XHR and the empty URL in breadcrumbs, so we should keep that open

[kunal649]

Looks good now, thank you!

A few small things:

• Can you update the description so it mentions href?
• We should rename Fixes #13168 -> Ref #13168. This PR covers the fetch error message, but the issue also mentions XHR and the empty URL in breadcrumbs, so we should keep that open

Done, sigrid

[s1gr1d]

Thanks for the updates! One last thing: the "Check file formatting" job fails on the new about:srcdoc row in fetch.test.ts (my suggestion was not properly, sorry 🙈). Running pnpm run format fixes it.