React Native - Immer with Expo.io Reducer returned undefined during initialization

[tomer-tgp]

🐛 Bug Report

I am trying to add immer to a react native expo app with redux.
I am getting this error:
React Native - Immer with Expo.io Reducer “user” returned undefined during initialization

To Reproduce

Before Immer (working)

import { LOGIN_ACTION } from '../actions/actionTypes';

const initialState = {
  user: false,
};

const User = (state = initialState, action) => {
  switch (action.type) {
    case LOGIN_ACTION:
      return {
        ...state,
        'user': action.user
      };

    default:
      return state;
  }
};

export default User;

After Immer (not working)

import produce from 'immer';
import { LOGIN_ACTION } from '../actions/actionTypes';

const initialState = {
  user: false,
};

const User = (state = initialState, action) => {
  produce((state, draft) => {
    switch (action.type) {
      case LOGIN_ACTION:
        draft.user = action.user;
        break;
    }
  });
};

export default User;

What am I doing wrong?

Here is the full error I am getting:

Reducer "user" returned undefined during initialization. If the state passed to the reducer is undefined, you must explicitly return the initial state. The initial state may not be undefined. If you don't want to set a value for this reducer, you can use null instead of undefined.

redux.js:366:22 forEach [native code]:0 assertReducerShape redux.js:359:32 combineReducers redux.js:422:23 index.js:4:31 loadModuleImplementation require.js:292:12 index.js:2 loadModuleImplementation require.js:292:12 App.js:5 loadModuleImplementation require.js:292:12 AppEntry.js:2 loadModuleImplementation require.js:292:12 guardedLoadModule require.js:179:45 global code :0

Expected behavior

Should work like react! I followed this example:
https://github.com/react-boilerplate/react-boilerplate/blob/master/app/containers/HomePage/reducer.js

[mweststrate]

return produce(.... Op di 30 jul. 2019 03:10 schreef tomer-tgp <notifications@github.com>:

…

🐛 Bug Report I am trying to add immer to a react native expo app with redux. I am getting this error: React Native - Immer with Expo.io Reducer “user” returned undefined during initialization To Reproduce Before Immer (working) import { LOGIN_ACTION } from '../actions/actionTypes'; const initialState = { user: false, }; const User = (state = initialState, action) => { switch (action.type) { case LOGIN_ACTION: return { ...state, 'user': action.user }; default: return state; } }; export default User; After Immer (not working) import produce from 'immer'; import { LOGIN_ACTION } from '../actions/actionTypes'; const initialState = { user: false, }; const User = (state = initialState, action) => { produce((state, draft) => { switch (action.type) { case LOGIN_ACTION: draft.user = action.user; break; } }); }; export default User; What am I doing wrong? Here is the full error I am getting: Reducer "user" returned undefined during initialization. If the state passed to the reducer is undefined, you must explicitly return the initial state. The initial state may not be undefined. If you don't want to set a value for this reducer, you can use null instead of undefined. redux.js:366:22 forEach [native code]:0 assertReducerShape redux.js:359:32 combineReducers redux.js:422:23 index.js:4:31 loadModuleImplementation require.js:292:12 index.js:2 loadModuleImplementation require.js:292:12 App.js:5 loadModuleImplementation require.js:292:12 AppEntry.js:2 loadModuleImplementation require.js:292:12 guardedLoadModule require.js:179:45 global code :0 Expected behavior Should work like react! I followed this example: https://github.com/react-boilerplate/react-boilerplate/blob/master/app/containers/HomePage/reducer.js — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#399?email_source=notifications&email_token=AAN4NBBJRJRS4TMANRTNIELQB6IHBA5CNFSM4IHXOLZ2YY3PNVWWK3TUL52HS4DFUVEXG43VMWVGG33NNVSW45C7NFSM4HCFSY4Q>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AAN4NBAO6TUPIEZG2N6GECTQB6IHBANCNFSM4IHXOLZQ> .

[tomer-tgp]

Thank you! I missed it because of the implicit return of es6 arrow function.

[bleedingAyush]

This must be added to the docs.