Should this be an RFC?

• This is not a substantial change

Which package is this a feature request for?

React (@lit/react)

Description

The current react element wrapper sets many properties later, during a layout effect.

There is a short list of properties considered part of react that are assigned at element creation time:

const reservedReactProperties = new Set([
  "children",
  "localName",
  "ref",
  "style",
  "className",
]);

This poses some trouble when porting lit elements that refer to each other by id. For example:

<custom-element-a id="an-element"></custom-element-a>
<custom-element-b target="an-element"></custom-element-b>

Because the id is not set at first render, the element cannot be found in the connected callback phase of <custom-element-b>

Alternatives and Workarounds

I have made a fork of the custom element wrapper that treats the id property as a react property and sets it earlier.