Misleading error message "URL must not be a blank string" when URL is a non-string value which does not stringify to a fully valid URL with a hostname

[mitranim]

What version of Bun is running?

1.2.18+0d4089ea7

What platform is your computer?

Darwin 24.3.0 arm64 arm

What steps can reproduce the bug?

Any of the following (and more):

await fetch(undefined)
await fetch(123)
await fetch({toString() {return `/some_path`}})

What is the expected behavior?

Something more precise, like:

fetch() URL must have a hostname

What do you see instead?

fetch() URL must not be a blank string

Additional information

Link to offending line in Bun sources:

bun/src/bun.js/webcore/fetch.zig

Line 1448 in bd23218

return globalObject.ERR(.INVALID_ARG_TYPE, fetch_error_blank_url, .{}).throw();

[linear]

ENG-19787 Misleading error message "URL must not be a blank string" when URL is a non-string value which does not stringify to a fully valid URL with a hostname

[Ayush-k-Shukla]

Hii @mitranim i would love to work on it can you please assign it to me. Thanks :)

[RiskyMH]

Also note node errors with these (each line for each of the example code):

TypeError: Failed to parse URL from undefined
TypeError: Failed to parse URL from 123
TypeError: Failed to parse URL from /some_path

and yeah bun throws fetch() URL must not be a blank string., a generic error for all cases

[mitranim]

@Ayush-k-Shukla
Can't. Not a contributor here. 🙂

[its-me-mhd]

Hi! I'd like to work on this issue.

I've already implemented a fix that adds specific error messages for different URL validation scenarios (empty URLs vs missing hostnames vs invalid URLs) while maintaining backward compatibility.

Can I be assigned to this issue?
Thanks!

[tysoncung]

I noticed this issue. Have you tried checking the error logs or console output? That might help narrow down the root cause. I'd be happy to help investigate if you can share more details about your environment (OS, version, etc.).