Main.hx

class Main extends luxe.Game {

    override function config(config:luxe.GameConfig) {
        
        config.preload = PreloadAssets.parcel;

        return config;

    }

  ...
    
}

PreloadAssets.hx

//An example of a luxe early alpha preload parcel macro.
//The macro loads a preload json file, and applies it 
//to a static member that the config function can use.

//You could also use filesystem reads to populate this as an exercise.

#if !macro

@:build(PreloadAssetList.build())
class PreloadAssets {
    //this class gets populated by the build macro!
    //it looks like this, a variable named parcel:
    //var parcel: { json:[...], text:[...], }
    //and it is exactly the contents in the json
}
#end

private typedef PreloadParcel = {
    ? bytes: Array<Dynamic>,
    ? texts: Array<Dynamic>,
    ? jsons: Array<Dynamic>,
    ? textures: Array<Dynamic>,
    ? fonts: Array<Dynamic>,
    ? shaders: Array<Dynamic>,
    ? sounds: Array<Dynamic>
}

class PreloadAssetList {
    macro public static function build():Array<haxe.macro.Expr.Field> {
        #if macro
            var path = haxe.macro.Context.resolvePath('preload.json');
            var contents = sys.io.File.getContent(path);
                //instead of parsing the json file, you could use sys.Filesystem  
            var parcel:PreloadParcel = haxe.Json.parse(contents);

                //The fields array is the list of class fields/members in our PreloadAssets class.
            var fields:Array<haxe.macro.Expr.Field> = haxe.macro.Context.getBuildFields();
                        
                //we add one, and fill it with the contents of our parcel json
            fields.push({
                name: "parcel",
                doc: "The parcel, as defined inside of preload.json",
                access: [APublic, AStatic],
                kind: FVar(macro :PreloadParcel, macro $v{parcel}),
                pos: haxe.macro.Context.currentPos(),
            });

            return fields;
        #end
    }
}