Issue with rehydrate on v3

[felipemartim]

I'm having a problem regarding the new version of redux-persist that may be very specific to the project I'm working on right now, but, nevertheless, I'll describe it here.

I have a logout action that resets all reducers to the initial state and I'm also using autoRehydrate to load the previous state stored in AsyncStorage (it's a react native app). The issue happens when I open the app, get the state rehydrated and I try to logout immediately after that. The state is never persisted.

By calling "persistStore", the "createPersistor" function is invoked and a new persistor is created with its lastState set to the initial state. The persistor is then paused, which is resumed only after rehydration. That means the "lastState" on the persistor is still the initial state, even after rehydration. When I dispatch my logout action, the new state is compared to the "lastState" and as both are the same, nothing gets persisted in AsyncStorage. If I reload the app the state is still the same before I logged out.

I don't know if this is the intended behaviour or if it's a bug. Is there any reason why the persistor needs to get paused during rehydration?

[rt2zz]

persistor is paused until getStoredState is complete otherwise there could potentially be a race condition where state is stored via the persistor before the old state is retrieved, thus overwriting the state that was intended for rehydration.

Your particular case is pretty interesting, we should definitely account for it. One option which I have no fully considered the consequences of would be to set lastState to be the value of the restoredState. This would presumably need to be done when resume() is called.

As a short term workaround you might consider cloning your initialState on logout, so instead of

myReducer (state = initialState, action) {
// ... old way
case 'LOGOUT'
  return initialState

// ... new way
case 'LOGOUT'
  return {...initialState}

[felipemartim]

Thanks for the quick reply!

I believe that short term workaround wouldn't work for me, due to the fact that my initial state is an Immutable Record. But I'll give it a try later. For now, I'm just returning the initial state with a "hasSignedOut" flag set to true, so it will be different than the initial state.

And I also believe setting lastState to the restoredState would solve the issue. 👍

[gullitmiranda]

the comparison of objects in javascript does not work very well. Thus the state[key] == reducedState[key] (in /src/autoRehydrate.js#L29) will always return false if the content is an object.

e.g.:

$ node --version
v6.0.0

$ node
> a = {"_status":null,"data":null,"entities":{},"model":{},"errors":null,"error":null}
{ _status: null,
  data: null,
  entities: {},
  model: {},
  errors: null,
  error: null }
> b = {"_status":null,"data":null,"entities":{},"model":{},"errors":null,"error":null}
{ _status: null,
  data: null,
  entities: {},
  model: {},
  errors: null,
  error: null }
> a == b
false
> a !== b
true

[felipemartim]

@gullitmiranda, as I'm using Immutable.js Records, this equality check returns true. However, after upgrading to 3.1.0, the issue got solved for me, so I'm closing this.

Thanks @rt2zz !

[rt2zz]

@felipemartim I forgot to update here, we now set initialState to an empty object, so state will always persist after the first load, thus solving your issue and also enabling https://github.com/wildlifela/redux-persist-migrate

@gullitmiranda that is true, but in idiomatic redux if you do not modify state you return the object as is with referential equality. e.g.

let a ={}
let b = {}
a === b // false
a === a // true