error in dev mode if global fetch is used with relative URL

[Rich-Harris]

closes #7976

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[Conduitry]

What happens if someone uses a protocol-relative URL like //foo/bar? This check would fail to catch it and it would (I think) then still fail with the global fetch.

Can we instead just check something simpler like that the URL matches /^\w+:\/\//? Or heck, just hard code http:// and https:// since I don't think anything else would succeed anyway?

[Rich-Harris]

The check would work — new URL('//foo.com', 'fake://fake').protocol === 'fake:'. But yeah, a regex is probably simpler. I opened a suggestion

[Conduitry]

Oh, whoops, not sure what I was thinking there anymore. I do still like the regex though.

[dummdidumm]

Approving the regex approach. Hardcoding http(s) would make things like tauri apps etc impossible to use the global fetch