Make the thunk params first and then spread other params

[emileber]

Disclaimer: I'm aware that this is not backward compatible.

Current behaviour

Right now, an action callback receives the thunk params last (source):

result = fn(...args, {getState, dispatch, extra});

Problem

It's harder to use optional params or just to validate them.

const myAction = createActionThunk('MY_ACTION', (a, b, { getState }) => {
  // do something with getState
  if (!b) {
    // do something or reject
  }
  return fetchData(a, b);
});

Then, calling myAction(a) will fail either because of the { getState } param destructuring, or because b is always present (as the thunk params object).

Proposition

Just place the thunk params object first, then spread the args.

result = fn({getState, dispatch, extra}, ...args);

Then, our action with optional params and/or validation will always work.

const myAction = createActionThunk('MY_ACTION', ({ getState }, a, b) => {
  // do something with getState
  if (!b) {
    // do something or reject
  }
  return fetchData(a, b);
});