URLSearchParams should accept an iterable

[fregante]

This works in the browser, but the TS definition doesn't allow it:

new URLSearchParams(new FormData(document.querySelector('form')));

The type is currently:

declare var URLSearchParams: {
    prototype: URLSearchParams;
    new(init?: string[][] | Record<string, string> | string | URLSearchParams): URLSearchParams;
};

The specification says that it should accept a "sequence", not specifically an array https://url.spec.whatwg.org/#concept-urlsearchparams-new

[saschanaz]

Currently the blocker is #222, because

1. We have to emit a new signature with an iterable argument in *.iterable.d.ts (and keep the current one for es5 support).
2. The current declare var pattern cannot be extended, so we can't add signatures via *.iterable.d.ts.

[Ryan1729]

The current definition of URLSearchParams is also missing some methods that return iterators. Specifically these ones (copied from @types/node):

    entries(): IterableIterator<[string, string]>;
    keys(): IterableIterator<string>;
    values(): IterableIterator<string>;

I suppose those are probably blocked on the same issue.

[saschanaz]

@Ryan1729 Those are available when you set target: es2015 or higher.

https://github.com/microsoft/TSJS-lib-generator/blob/353a0cfc53b97bcd3d105b93f64f74ad5ce394a9/baselines/dom.iterable.generated.d.ts#L243-L257