Spread operator doesn't work with "form" and "list" attributes

[imkremen]

Describe the bug
I'll try set list and form with spread operator:

let [type, form, list] = ['text', 'myID', 'listID'];
let props = {type, form, list};

It works in regular case:

<input type={type} form={form} list={list}>

But fails with spread operator:

<input {...props}>

Logs
Firefox: setting getter-only property "form"
Chrome: Cannot assign to read only property 'form' of object '#<HTMLInputElement>'

And if we remove "form" attribute:
Firefox: setting getter-only property "list"
Chrome: Cannot assign to read only property 'list' of object '#<HTMLInputElement>'

To Reproduce
REPL

[Conduitry]

This looks like another manifestation for an overarching problem which might not actually have its own issue (just a few related open issues) - namely, that we don't know whether each prop that's getting spread should be set as an attribute or as a property on the element. For non-spread props, we can look this stuff up at compile time, and just emit the correct code. I don't think we have a really good way to handle this for spread props (where this needs to be determined at runtime) without shipping a big list of properties vs attributes in the compiled code, which we'd really like to avoid doing.

The helper we're using right now for this is:

export function set_attributes(node: Element & ElementCSSInlineStyle, attributes: { [x: string]: string }) {
	for (const key in attributes) {
		if (key === 'style') {
			node.style.cssText = attributes[key];
		} else if (key in node) {
			node[key] = attributes[key];
		} else {
			attr(node, key, attributes[key]);
		}
	}
}

We set an attribute if one is available on the DOM object, otherwise we use an attribute. This breaks when it's a read-only property. It also doesn't handle when the property has a different name than the attribute, apart from the one special case of style.

I recall it being suggested somewhere I can't find that one possibility would be to fall back to setting it as an attribute if node[key] = attributes[key]; fails. This might be the best we can reasonably do. This definitely is an area that needs work.

[Conduitry]

A good idea from @pngwn: Check for Object.getOwnPropertyDescriptor(node.__proto__, key).set rather than key in node. These read-only properties don't actually have setters, which we can check for at runtime. Actually, we should probably do Object.getOwnPropertyDescriptors(node.__proto__) once at the beginning, and then do the lookups in that, which I imagine would be faster.