Types - Interface Assert, rootElement should also be null

[MrChocolatine]

Current signature of the method dom():
https://github.com/simplabs/qunit-dom/blob/6c31d65d825c8c09fab1c4f604b8a89945c06e11/lib/qunit-dom.ts#L10

But it is not completely accurate and triggers an error when rootElement comes from a basic querySelector():

const myTable = this.element.querySelector(/* my-selector */)
assert.dom('tbody > tr', myTable).exists({ count: 2 })
// -------------------------^
// const myTable: Element | null
// Argument of type 'Element | null' is not assignable to parameter of type 'Element | undefined'.
//   Type 'null' is not assignable to type 'Element | undefined'.

rootElement should also be accepted as null:

 dom(target?: string | Element | null, rootElement?: Element | null): DOMAssertions; 

[Turbo87]

hmm... I'm not sure I agree. If that querySelector() call returned null then what would you expect would happen?

Passing in an element will use that element as the root element. Not passing in anything should default to using the default root element. But explicitly passing in undefined or null seems like a bug to me, no?

[MrChocolatine]

I kind of agree @Turbo87 but not entirely.

hmm... I'm not sure I agree. If that querySelector() call returned null then what would you expect would happen?

Nothing. The same that would happen with undefined.

On the other hand, why should we have to do something like this every time to specifically match with the signature?
It seems a bit tedious to me.

const myTable = this.element.querySelector(/* my-selector */)
assert.dom('tbody > tr', myTable || undefined).exists({ count: 2 })

The thing is, *Element | null is literally the common signature of types returned by every* methods/properties to reach a DOM element.
* Okay I did not check absolutely every methods and properties but querySelector(), getElementById(), ownerElement, activeElement ... The list goes on.

[MrChocolatine]

Any update on this please :)?

The type returned by querySelector() being Element | null (like many other DOM methods), it does not match the types of the second argument rootElement of assert.dom().

But explicitly passing in undefined or null seems like a bug to me, no?

Even if, in the context of a test, we know our element should exist me might have made a mistake in the selector and null would be implicitly returned (then the default root element would be used), we should not have to do anything more with the following code:

const myElem = this.element.querySelector(/* my-selector */)
assert.dom('.some-class', myElem).exists({ count: 2 })