Add feature or document how to reset Apollo store

[stubailo]

For example, when the user logs out we might want to clear our some or all of the data on the client.

[abhiaiyer91]

There's way to achieve this today in Redux. We can compose a HO Root Reducer like

function superMegaRootReducer(state, action) {
   if (action.type === 'USER_LOGOUT') {
      state = undefined
   }
  return rootReducer(state, action);
};

What would be cool is next having a reset middleware, so when i want to do these resets, i can just hit an generic reset action type and handle some function i want to be called in the process.

https://gist.github.com/abhiaiyer91/a8a7ca18a8f9b11faa02c899165d942b

Exposing this could be a way to handle tons of things we know we want to do when a user resets

[stubailo]

Yep, just need to add some tests and make sure the client behaves correctly when all of the data disappears!

[abhiaiyer91]

Im thinking we should do the following

1. ship a Higher Order Reducer so people can reset state of any reducer they want.
2. Build in reset capability to apolloReducer
3. write tests
4. write docs

what do you think?

[stubailo]

What's the higher order reducer for?

[abhiaiyer91]

The higher order reducer is for people who want to reset their normal redux state based on the same state clearing the apolloReducer will have. Thoughts?

So essentially whatever we clear apolloReducer with i can wrap a redux reducer

someReducer: composeResetReducer(someReducer, {})

where composeResetReducer takes a reducer and some initial state

function composeResetReducer(reducer: Function, initialState: any): Function {
  return function composedReducer(state: any, action: Object): any {
    if (action.type === "RESET_STATE") {
      return initialState;
    }
    return reducer(state, action);
  };
}

Could be a nice little utility for peeps

[stubailo]

Hmm, I'd rather skip that for now - it doesn't seem relevant to Apollo IMO. I'd rather just document "Apollo uses the RESET_STATE action to reset, feel free to use that in your own reducer" or something like that.

I'd rather not get into the business of writing higher-order reducers for people, that sounds like a Redux thing.

But if you want to write a separate package for that, it would be fine to include that in the docs as a code example!

[abhiaiyer91]

Okay Step 1 function to use. https://github.com/abhiaiyer91/redux-reset

[timbotnik]

This is a real security issue for users on shared computers, is there currently a mechanism for clearing the state? @helfer @stubailo

[helfer]

I think the current workaround is to explicitly pass the store to apollo on construction, and then remove the reference to that store. I think setting the store content to null wouldn't be enough, because you also want to get rid of history. But then again, I don't know much about Redux, so I'll defer to the experts.

[WilliamHolmes]

FYI:
Your global REDUX state can be reset using...
type: 'RESET'

[timbotnik]

So I tried out a store reset using the mechanism described here, but I found the QueryManager threw an exception whenever I dispatched my RESET action.

The internal state for query listeners is actually the issue. If there are outstanding watched queries, it fails inside the broadcastQueries function, since queries is {}, and then you end up here and explode when dereferencing queryStoreValue.

And just to clarify - there seems to be no issue if you make sure that all the watched queries are stopped BEFORE resetting the store (although I am not sure there isn't some other state that might need cleaning up as well).

From my perspective i think a reset API makes sense, since

1. Otherwise I’d have to learn about how to make a reset reducer myself and this is not exactly straightforward. Actually just to add a reset reducer you have to create your own redux store for Apollo, and you lose some nice things like the crash reporter and the hooks for redux dev tools.
2. We have in-memory state that also needs to be cleaned up before we can safely clear the store.
3. We might not always use redux as a store?

[Poincare]

Should now be fixed w/ PR #314.

[rogchap]

Not sure if this is a complete example on how to reset the store (especially for a logout scenario). The resetStore func is hidden inside QueryManager; and there is no (clear) way to stop queries that are in flight.