Type narrowing for selection + item api

[Kelin2025]

Suppose that we have a list of widgets. Widget looks like this:

type Widget = {
  id: string;
  type: string;
  options: Record<string, any>;
};

options type depends on widget type. For example

type SwapWidget = Widget & {
  type: 'swap';
  options: { from: string; to: string; value: number };
};

It'd be cool to create a single kv and then create sets of item apis for each widget type

export const widgets = createListApi<Widget, string>({
  keygen: (widget) => widget.id || `id-${Math.random().toString(36).slice(2, 10)}`,
});

export const swapWidgets = createSelection(
  widgets,
  (widget): widget is SwapWidget => widget.type === 'swap'
);

export const swapWidgetApi = createItemApi({
  kv: widgets,
  events: {
    fromChanged: widgets.mapItem(({ options }, from: string) => ({ options: { ...options, from } })),
    toChanged: widgets.mapItem(({ options }, to: string) => ({ options: { ...options, to } })),
    valueChanged: widgets.mapItem(({ options }, value: string) => ({ options: { ...options, value } })),
  },
});

However, we can't narrow swapWidgetApi to work with swap widgets only. And, as a result, types can't be narrowed too

What if we could create api directly from selection? Like swapWidgets.mapItem, or pass swapWidgets instead of widgets as kv param?

[Kelin2025]

Alternatively, we could create separate lists and combine them into one. Like:

export const swapWidgets = createListApi<SwapWidget, string>(...)
export const transactionsWidgets = createListApi<TransactionsWidget, string>(...)

export const allWidgets = combineLists({
  lists: [swapWidgets, transactionsWidgets]
})

This will solve type narrowing problems but we should also be able to create common api somewhere (like allWidgets.removeItem, for example)