URL constructor not spec compliant

[Upsilon-Iridani]

Description

When supplying the URL constructor with a second argument, 'base', paths aren't resolved correctly. see https://developer.mozilla.org/en-US/docs/Web/API/URL/URL#base

The error is visible here:

react-native/packages/react-native/Libraries/Blob/URL.js

Lines 80 to 107 in 900b625

	constructor(url: string, base?: string | URL) {
	let baseUrl = null;
	if (!base || validateBaseUrl(url)) {
	this._url = url;
	if (!this._url.endsWith('/')) {
	this._url += '/';
	}
	} else {
	if (typeof base === 'string') {
	baseUrl = base;
	if (!validateBaseUrl(baseUrl)) {
	throw new TypeError(`Invalid base URL: ${baseUrl}`);
	}
	} else {
	baseUrl = base.toString();
	}
	if (baseUrl.endsWith('/')) {
	baseUrl = baseUrl.slice(0, baseUrl.length - 1);
	}
	if (!url.startsWith('/')) {
	url = `/${url}`;
	}
	if (baseUrl.endsWith(url)) {
	url = '';
	}
	this._url = `${baseUrl}${url}`;
	}
	}

Steps to reproduce

console.log(new URL('/absolute/path', 'https://example.com/base-url/').href);
// prints:       https://example.com/base-url/absolute/path
// expected:     https://example.com/absolute/path

React Native Version

0.73

Affected Platforms

Runtime - iOS

Output of npx @react-native-community/cli info

N/A

Stacktrace or Logs

N/A

Reproducer

N/A

Screenshots and Videos

No response

[react-native-bot]

Warning

Could not parse version: We could not find or parse the version number of React Native in your issue report. Please use the template, and report your version including major, minor, and patch numbers - e.g. 0.76.2.

[react-native-bot]

Warning

Missing reproducer: We could not detect a reproducible example in your issue report. Please provide either:

• If your bug is UI related: a Snack
• If your bug is build/upgrade related: a project using our Reproducer Template
• Otherwise send us a Pull Request with the RNTesterPlayground.js edited to reproduce your bug.

[react-native-bot]

Warning

Could not parse version: We could not find or parse the version number of React Native in your issue report. Please use the template, and report your version including major, minor, and patch numbers - e.g. 0.76.2.

[cipolleschi]

@Upsilon-Iridani 0.73 is out of support and it won't receive any further updates. The oldest supported version right now is 0.76. Can you check if the problem persists there as well?

[Upsilon-Iridani]

I could only reproduce it in a snack by selecting expo 0.49, so it might already be solved. Then the code I linked in the issue should probably be deleted, as it appears dead/unused.