Forbid lazy state return.

Even though the following “kind” of action is frowned upon, we could go one step further and ignore state updates (as well as re-renders).

myAction(state) {
  state.prop = 1
  return state
}

The change requires we simply check if the appState === newState and return early.

/cc @naugtur @zaceno @lukejacksonn

[jorgebucaran]

@jamen Yep, we are on sync now. 😉

And my opinion about that was expressed here.

tl;dr: This is a do-it-at-your-own-risk kind of “feature”; I won’t force you to do things in a particular way (although you should), but I am not going to go “out of my way” to let you do it either (unless there’s some trivial change that allows it).

[zaceno]

Oh… I get it now! Mutating state in props is unsafe because of the shallow merge. While each action gets a new state instance, the properties containing objects will not be fresh instances.

Ok, so the unsafeness of mutating deep state properties is a completely separate issue to what’s being proposed here (because it would continue being unsafe, even if we did implement this).

…even so, I’m still not sure I like this proposal because it will be difficult to debug. I’ve written that sort of inappopriate actions in many places. This sort of “silent fail” would make refactoring harder. So if we eventually do take it in, it should be after we have a dev-build which can log warnings. Or failing that, make production builds throw errors terminating and providing stack traces.

@okwolf Thanks for giving that example! I was actually aware of the object-spread operator to use in this case, but for me personally, I don’t consider it a solution as it is only a stage-3 proposal and not yet standard ecmascriot.