Poor typing usability

[novemberborn]

While working on dojo/examples#56 I found it nearly impossible to correctly type actions.

There is an assumption that the options passed to the do() implementation have an event object, and that object has a target property. That makes sense when actions are used as event listeners but often actions call other actions, passing an arbitrary object.

Furthermore, the do() method is assumed to return a Task which resolves with the (same type as) the target.

Correctly changing the typing of an action requires three types (DoOptions, TargettedEventObject and ActionState). This requires a fair amount of understanding of the action internals.

Typing an action which handles keypress events is nearly impossible since the KeyboardEvent type is not compatible with the TargettedEventObject. It has a target of course (an HTMLElement), but the do() implementation may return an entirely different object.

---

I'd like to see an interface closer to this:

interface ActionMixin<T, O> {
  do(options?: O): Task<T>;
}

type Action<T, O> = Stateful<ActionState> & ActionMixin<T, O>;

The default createAction export should create Action<any, any> instances. It should take type arguments, e.g. createAction<any, KeyboardEvent>() should create an action that can handle keyboard events. In the TodoMVC example, a createAction<any, Item>() should create an action that is called with todo items.

We could export other constructors to make it easier to create the current "targeted event" actions.

---

I'm not sure whether ActionState deserves to be a generic. It's tempting but we can't provide default values for generics, and the more arguments Action takes the harder it is to customize the typing.

[kitsonk]

• Promise not Task
• Callers should NOT care about the return value, no matter what.
• .do() executor should always return Promise<void>
• Type the .do() arguments to be more generic and flexible
• Work better with dojo-app by typing registryProvider in factory options and .configure()
• Generic registryProvider

[kitsonk]

Closing as we would address this if we would ever revive this package.