Passing a single string as a sequence<DOMString> generates a Vec<DOMString>

[ferjm]

With an interface like:

dictionary BarOptions {
  required sequence<DOMString> baz;
};

interface Foo {
  void bar(BarOptions options);
};

passing a single string like:

  var foo = new Foo();
  foo.bar({ baz: "string"});

generates a [DOMString("s"), DOMString("t"), DOMString("r"), DOMString("i"), DOMString("n"), DOMString("g")].

I believe this should throw a TypeError instead, like in https://github.com/w3c/web-platform-tests/blob/master/performance-timeline/po-observe.any.js#L12

[SimonSapin]

https://heycam.github.io/webidl/#es-sequence defines that a WebIDL sequence<T> is created from a JS object through its @@iterator method, which for strings iterate over the code points. So this behavior looks expected?

[ferjm]

I am not sure ... whatwg/webidl#266 Is DOMString a string wrapper?

[saschanaz]

Can't reproduce this:

new MutationObserver(() => {}).observe(document.body, { attributeFilter: "abc" });
// TypeError: Value is not an object, as expected.