ActionType is returning `never`

[iansan5653]

Description

The ActionType helper is returning never instead of the correct mapping, despite using a very simple actions file.

I'm probably doing something incorrectly, but if so, I can't find it.

Mandatory info

• [x] Are you extending internal types to enable type-free syntax with createReducer?

I'm trying to, but it's not working:

import {ActionType} from "typesafe-actions";
import * as actions from "./actions";

export type RootAction = ActionType<typeof actions>; // results in `never`

declare module "typesafe-actions" {
  interface Types {
    RootAction: RootAction;
  }
}

• [x] Did you checked compatibility notes and migration guides?

How to Reproduce

This is reproduced with simply the types.d.ts file above, and the actions.ts file below:

import {createAction} from "typesafe-actions";
import * as api from "utilities/api";

export const example = createAction("EXAMPLE", () => 3);

CodeSandbox Link

https://codesandbox.io/s/crazy-snyder-meokt

Expected behavior

I expect the type of RootAction to be {type: "EXAMPLE"}.

Project Dependencies

• Typesafe-Actions Version: 5.1.0
• TypeScript Version: 3.7.5

[christophemenager]

Hello,

I think you should write :

export const example = createAction("EXAMPLE", () => 3)();

You have forgotten the () at the end !

[piotrwitek]

Thanks @christophemenager you are right! It's missing () at the end!

[mnbattaglia]

Hey @piotrwitek . I was banging my head with this issue for more than two hours. I have a working app in v4 and wanted to migrate to v5. I'm using an actor creator with a plain object like this example (https://github.com/piotrwitek/typesafe-actions#actiontype) and then using ActionType to create my RootAction type. Finally, I'm creating my reducer by providing generics like this:

import {ActionType, createAction, createReducer} from 'typesafe-actions'

export type State = Readonly<{
    some: string,
}>

const actions = {
    action1: createAction('action1'),
    nested: {
        action2: createAction('action2'),
        moreNested: {
            action3: createAction('action3'),
        },
    },
};
export type RootAction = ActionType<typeof actions>;
export const reducer = createReducer<State, RootAction>({some: "test"})
    .handleAction(actions.action1, (state, action) => {
        return {
            ...state,
        }
    })

This will cause the following errors in the handleAction method:

Error:(18, 19) TS2345: Argument of type '<TPayload = undefined, TMeta = undefined>() => ActionCreatorBuilder<"action1", TPayload, TMeta>' is not assignable to parameter of type '((...args: any[]) => never) | ((...args: any[]) => never)[]'.
  Type '<TPayload = undefined, TMeta = undefined>() => ActionCreatorBuilder<"action1", TPayload, TMeta>' is not assignable to type '(...args: any[]) => never'.
    Type 'EmptyActionCreator<"action1">' is not assignable to type 'never'.
Error:(18, 37) TS7006: Parameter 'state' implicitly has an 'any' type.
Error:(18, 44) TS7006: Parameter 'action' implicitly has an 'any' type.

Luckily, I found this thread and the reason was the missing () at the end of action creation. Is my reasoning ok? Don't you think this should be added in the migration guide?

Thanks!

[mnbattaglia]

Sorry @piotrwitek , after re-reading the migration guide, in step 3 I can see in the "after" code of createAction there is actually a () at the end. Maybe you can highlight it somehow for idiots like me so they don't waste so much time

[piotrwitek]

@mnbattaglia you can send a PR with edit in the docs and I will merge ;)