undefined URL constructor base argument for Safari

[BarryThePenguin]

TypeScript Version: 3.6.4

Though the types are still the same

TypeScript/lib/lib.dom.d.ts

Lines 16068 to 16073 in a03227d

	declare var URL: {
	prototype: URL;
	new(url: string, base?: string | URL): URL;
	createObjectURL(object: any): string;
	revokeObjectURL(url: string): void;
	};

Search Terms:

undefined URL constructor base argument Safari

Code

class FooURL {
  private _url: URL
  
  constructor(url: string, base?: string | URL) {
    this._url = new URL(url, base)
  }
}

// Throws `TypeError: Type error` in Safari
new FooURL('https://example.com')

Expected behavior:

The constructor for URL should not allow undefined constructor argument for base

Something more appropriate could look like

new(url: string): URL; 
new(url: string, base: string | URL): URL; 

Actual behavior:

Both Safari Version 13.0.2 (14608.2.40.1.3), and Safari Technology Preview Release 94 (Safari 13.1, WebKit 14609.1.6.1) throw an error when the base constructor argument is undefined.

Essentially typescript treats new URL('example.com', undefined) as valid

Other browsers are able to handle this case just fine.

I did look at the whatwg spec

Maybe it's a problem with how TSJS-lib-generator generates optional arguments?

I'm not sure if this is something that should be handled by TypeScript. Interested to hear what others think!

Playground Link

Related Issues:

#15246

[trotyl]

I have report this to core-js that Safari doesn't have valid URL implementation: zloirock/core-js#656, the types are indeed correct.

[RyanCavanaugh]

TS doesn't really distinguish between passing undefined to a function vs skipping the argument entirely. This is convenient 95% of the time and the remaining 5% breaks libraries that are written in an indirection-hostile way. Anyway we're not here to encode Safari's spec compliance bugs into our lib file.

[BarryThePenguin]

Ahk, I was unsure if that was the case. That clarifies things for me. Thanks for the response!