I'd like to have config properties that are expressions. I'd also like those expressions to be able to use feature properties, like so:

{
  "schema": {
    "room-color": {
      "type": "color",
      "default": ["case", ["==", ["get", "room-type"], "administrative"], "red", "blue"]
    }
  },
  "layers": [
    "id": "rooms-fill",
    "type": "fill",
    "paint": {
      "fill-color": ["config", "room-color"]
    }
  ]
}

This is only partly supported ATM, because of (at least) two issues I bumped into while stepping through the evaluation code path in one of the workers:

1. The expression assigned to fill-color above is considered feature constant, and so feature data is not loaded during evaluation. This can be hacked around by wrapping the whole thing into e.g. a let with a get – but this is suboptimal (think ["let", "_" ["get", "room-type"], ["config", "room-color"]]).

2. Evaluating a match expression in the worker fails and defaults to the "otherwise" branch, if the expression being evaluated is a config expression. This happens here as the typeOf(input) === this.inputType check returns false, probably because the type constants in the worker are not referentially the same as the {kind: ...} value from the unserialized version of the config expression from the main thread(?).

mapbox-gl-js version: 3.11.0

browser: Arc

Link to Demonstration

https://codesandbox.io/p/sandbox/lxfnlg?file=%2Findex.html%3A39%2C20

(If both of these issues are fixed, one of the squares should be red.)