Argument of type 'unknown' is not assignable to parameter of type 'Action<string>'.

[andreisocaciu]

When trying to match an action in a middleware, I get this Typescript error: Argument of type 'unknown' is not assignable to parameter of type 'Action<string>'. typescript(2345)

Version: @redux/toolkit@2.0.0-rc.0

Codesandbox link: https://codesandbox.io/p/sandbox/kind-fog-7nxp6k?file=%2Fshared%2Fcounter.middleware.ts%3A5%2C31-5%2C37

[EskiMojo14]

yep - you need to check it's an action first. Redux now exports an isAction type predicate that can do this for you:

import { isAction, Middleware } from "@reduxjs/toolkit";
import { incrementByAmount } from "./counter.slice";

export const counterMiddleware: Middleware = (store) => (next) => (action) => {
  if (isAction(action) && incrementByAmount.match(action)) {
    console.log("action dispatched", action);
  }
  return next(action);
};

[EskiMojo14]

fyi we're now planning to move the isAction call inside .match so you won't have to do this yourself (#3897) - we're also gonna move isAction to the core package (reduxjs/redux#4620) and re-export it from RTK, since it's likely useful for people using handwritten redux patterns too