Reducers (ex-'stores') must have a default return value for state to be initialized properly?

[burmisov]

Just spent some half an hour figuring this out.
Say I only had one action type to process in my reducer, so, based on my experience with 'vanilla flux', I did it like this:

export default function myReducer (state = initialState, action) {
  switch (action.type) {
   case THE_ONE_ACTION_I_LISTEN_TO:
     return { ...state, ...someNewStuff };
  }
}

And (of course it's obvious to me now) I get an undefined state before the first action run, not the initialState. So I had to add the

default: return state;

to correctly process the '@@init' action type. AFAIK that's nowhere to be found in the docs currently, guess it's just implied, but maybe mentioning it somewhere could save someone else a bit of time.

[gaearon]

Sorry for this.

I'd accept a PR checking that the return value of every store function inside composeStores is not undefined. This should cover the most common use case. Folks not using composeStores are assumed to know what they're doing anyway.

This will also need a test in composeStores.spec.js.

[gaearon]

(And they're going to be composeReducers in the next version... But we're not there yet ;-)

[gaearon]

Work in progress on fixing this: #174

[gaearon]

@burmisov Thoughts on #191?

[gaearon]

Superseded by #191.