DOMStringMap has no mechanism to add/remove/change values

[parlough]

DOMStringMap, primarily returned by HTMLElement#dataset does not provide any mechanism to set or access its values.

Would be nice if it implemented something like Map<String, String> if that was possible :)

[kevmoo]

I've ran into this, too! CC @srujzs

[srujzs]

I'm surprised we don't emit some properties already:

https://github.com/w3c/webref/blob/8d7678e1740d00c3b79ebf70013d0448b23e3c8b/ed/idl/html.idl#L161

It might be due to us not handling getter and setter? Maybe we should emit them using [] and []=. https://webidl.spec.whatwg.org/#idl-special-operations

That being said, I don't think we can feasibly implement Map (or any Dart collections type), but hopefully the indexing operations are enough!

[adrianlmm]

This one is a show stopper for me, I can't start the migration from 'dart:html' to 'web' until it gets fixed.

[srujzs]

Can you describe a bit more on what's affecting your migration? If it's the above indexing operators, you can define your own external extension members on any interop type if they're not available: https://dart.dev/interop/js-interop/usage#extension-members-on-interop-types e.g.

import 'dart:js_interop';
import 'dart:js_interop_unsafe';

extension on DOMStringMap {
  external String operator [](String name);
  external void operator []=(String name, String value);
  void delete(String name) => this.delete(name.toJS);
}

Matching the definition here: https://html.spec.whatwg.org/multipage/dom.html#embedding-custom-non-visible-data-with-the-data-*-attributes:domstringmap-3.