fix: allow calling fetch for any scheme

[danielniccoli]

Fixes #10657

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[danielniccoli]

Continuation of #10656

That sounds fine, but I think your translation from text to reflex omitted uppercase letters and "+"

Originally posted by @benmccann in #10656 (comment)

The "+" is in there, hidden in plain sight. \d+ does match on digits and plus because its within square brackets.

The uppercase letters are also matched due to insensitive flag.

[benmccann]

Thanks. This looks good to me, but could we refactor this shared logic into a util method like is_relative_url probably in src/utils/url.js?

[danielniccoli]

@benmccann, I have put some thought into your suggestion and I think it would be better to not have a function and accept that this regex will be used at two places. The test answers the questions "Is this a relative URL?" with an approximation that is just good enough for the specific case. For example, it will tell you that "mailto:jon.doe@example.com" is an absolute URL. But it's a URI and neither absolute nor relative. (Which we can ignore because a developer wouldn't do this.) Putting this into a function may encourage devs to use it elsewhere, which could cause unintentional side effects. Of course, we could do proper validation and cover all the edge cases as well, but that would introduce unnecessary complexity.

I do not have an alternative suggestion. I added some comments to the two lines to clarify what is tested and why.

Let me know your thoughts. If you think the concerns are negligible, I will refactor.

[benmccann]

That's a fair point. How about extracting the regex out into a constant like SCHEME_REGEX in utils/url.js or something along those lines?

[danielniccoli]

@benmccann I like that. There's already a scheme variable declared, but it's not exported, so I think we can get away with an additional exported constant? (I don't want to rewrite the already present one, because I don't know what resolve() does and where it's used.)

import { BROWSER } from 'esm-env';

// <<<<<<<<<<<<<<<
/** @constant - Matches a URI scheme (https://www.rfc-editor.org/rfc/rfc3986#section-3.1)
    @type {RegExp}
    @default
*/
export const SCHEME = /^[a-z][a-z\d+\-.]+:/i;
// >>>>>>>>>>>>>>>

const absolute = /^([a-z]+:)?\/?\//;
const scheme = /^[a-z]+:/;

/**
 * @param {string} base
 * @param {string} path
 */
export function resolve(base, path) {

[benmccann]

Just go ahead and update the existing one. resolve is used during prerendering. I don't think anything should be negatively affected by updating the existing scheme regex with a more accurate one

[danielniccoli]

Refactored.

[benmccann]

Thanks for the great PR!