AppThunk pattern can't infer return type of thunk

[ProdigySim]

Using the AppThunk type, I may write some thunk that returns a promise:

export const incrementAsync = (amount: number): AppThunk => async dispatch => {
  dispatch(incrementByAmount(amount))
  return await Promise.resolve(amount);
};

But, AppThunk does not seem to infer the return type here, and just uses void. So, incrementAsync gets a type of (amount: number) => AppThunk<void>.

Using a classic signature like

export const incrementAsync = (amount: number) => async (dispatch: Dispatch) => {
  dispatch(incrementByAmount(amount))
  return await Promise.resolve(amount);
};

gives us a type for incrementAsync of const incrementAsync: (amount: number) => (dispatch: Dispatch) => Promise<number> which infers the thunk return type properly.

Probably consider this more of a feature request, but it would be neat if there were a pattern that could support both the return type & parameter type inference here.

[markerikson]

Yeah, it's a bit of a tradeoff. You should be able to do AppThunk<Promise<MyData>> for those cases where you need the promise result.

That said, this really isn't an issue that's specific to the template itself - it's more about documenting ways to use thunks with TS, which is better suited for the core Redux repo. If you can file a PR to update the core docs, I'd appreciate it. Thanks!

[ProdigySim]

You could define another helper like

function createThunk<T>(thunk: AppThunk<T>) { return thunk; }

Which seems to convince Typescript to infer the return type properly