Design and Implementation of Fair 2.0 Logic Syntax Sugar

Fair 2.0 is a dynamic framework for Flutter that enables runtime widget updates via a compiler; version 2.0 adds logic‑level syntactic sugar to improve layout‑logic mixing.

Syntax sugar is defined as language constructs that do not add functionality but improve readability; Fair's sugar aims to simplify mixed layout‑logic scenarios.

Three design options were considered: (1) handling logic entirely on the JS side, (2) delegating simple conditional logic to Dart while keeping layout generation on the DSL side, and (3) custom designs. Option 2 was chosen.

The architecture ensures “dual‑state” consistency so that the same code runs both in native Flutter and in the dynamic runtime, with a registration mechanism that exposes sugar methods to the Fair engine.

Example static implementation registers a Sugar.map method in Dart; dynamic registration is performed in FairApp setup, exposing the method via a provider map.

class Sugar {
    static List<T> map<T, E>(List<E> data, {T Function(E item) builder}) {
        return data.mapEach((index, item) => builder(item));
    }
}

Usage in a Flutter widget demonstrates calling Sugar.map(_list, builder: (item) { … }) to generate a list of child widgets.

class _State extends State<MapPage> {
  var _list = [10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 100];
  @override
  Widget build(BuildContext context) {
    return Scaffold(
        body: ListView(
          children: Sugar.map(_list, builder: (item) {
            return Container(
              child: Row(...),
            );
          }),
        ));
  }
}

The DSL generated from the sugar call contains a className: "Sugar.map" node with parameters pointing to the source list and a builder description, which the runtime iterates to produce the final widget tree.

{
    "body": {
        "className": "ListView",
        "na": {
            "children": {
                "className": "Sugar.map",
                "pa": ["^(_list)"],
                "na": {
                    "builder": { ... }
                }
            }
        }
    },
    "methodMap": {}
}

Currently Fair includes five built‑in sugars (if, ifRange, Map, etc.) and plans to expand based on community contributions.