dedup Headers types

[ry]

No description provided.

[ry]

@kitsonk ... with this change we have this unfortunate side-effect:

> ./target/debug/deno
> Headers.name
HeadersImpl

I'm sure we can workaround this somehow - but it's not immediately obvious to me how.

[ry]

I think in the case of HeadersImpl, it could be done in dom_iterable.ts

deno/cli/js/web/dom_iterable.ts

Lines 82 to 86 in 8397cd5

	// we want the Base class name to be the name of the class.
	Object.defineProperty(DomIterable, "name", {
	value: Base.name,
	configurable: true,
	});

however there are other classes, like URLSearchParams which would also have to be fixed.

[kitsonk]

Were it is meaningful, we just need to override it. I wouldn't put it in dom_iterable because that overloads what it does it... just something like the below and throw it in util somewhere:

export function setName(fn: Function, value: string): void {
  Object.defineProperty(fn, "name", { value, configurable: true };
}

You should be able to modify the class after you export it as well... so no need to assign it to any variable or anything.

[ry]

Yeah that would work... it is more overhead than just a normal class definition (not much, admittedly, and maybe none after snapshotting). Ultimately we're just working around our own (dis)organization - ideally the JS that gets executed would just be

class Header {
  // ...
}

not

class HeaderImpl {
  // ..
}
Object.defineProperty(HeaderImpl, "name", { "Header", configurable: true });

I don't have a good solution on how to get our TS to produce the optimal JS :/