Action subscribers do not wait for associated actions to resolve

[wa3l]

What problem does this feature solve?

I noticed that my store action subscribers were being called before the actions finish. Digging into the code, it looks like not only do action subscribers not wait on the actions to resolve, but they execute before the action. Mutation subscribers, on the other hand, seem to work as expected (call mutation first, call subscriber second). Since actions are often asynchronous (and vuex always wraps them with promises), I think it makes more sense to wait on the action and then call subscribers.

I wasn't sure if this was intentional or not, hence the feature request.

What does the proposed API look like?

I think something like the following would be more in line with what developers expect:

const result = entry.length > 1
      ? Promise.all(entry.map(handler => handler(payload)))
      : entry[0](payload);
result.then(() => this._actionSubscribers.forEach(sub => sub(action, this.state)));
return result;

I could open a pull request if that looks reasonable (will add tests, etc.)

[LinusBorg]

If you recap the discussions in #960 -> #929 -> #908 , the use case of this feature was to get informed of actions when they are dispatched, not some (maybe very long) time later when they have finished.

What you want is probably something else.

[wa3l]

@LinusBorg interesting, thanks for providing that context. I'm trying to implement undo/redo, which a bit different than logging in that mutations represent a state change, but actions represent the actual "history steps" in state that the user cares about undoing. Without a way to notify some centralized subscriber when an action resolves, there is no built-in way of tracking those "logical" history changes.

I can probably wrap all (or a subset) of my actions with a function that does the waiting/reporting for me. I saw the term "action enhancer" thrown around a couple of times, but the vuexfire docs weren't very clear. The problem with this solution is, after refactoring my existing store, if anyone in the future forgets or doesn't know to wrap their actions with this action wrapper, then they are suddenly excluded from the history tracking.

I understand that subscribeAction was not meant for this purpose, but would it make sense to create an asyncActionSubscribe() that does what I'm describing?

[ktsn]

I think extending subscribeAction to let the store notify after finished action would work.

For example:

store.subscribeAction({
  before () { /* called before dispatching action */ },

  after () { /* called after the returned Promise is resolved */ }
})

[wa3l]

@ktsn that would be awesome. I'll take a crack at it.

[johnmerced-ks]

Looking forward for this! Any idea when will this be released?

[wa3l]

@johnmerced the pr is here, waiting on Evan's review.

[johnmerced-ks]

@wa3l Awesome! We are looking forward for this! 👍 Thank you!

[jbgraug]

Any updates or deadline on this feature?

[winniehell]

@ktsn #1115 is merged and released, so this issue can probably be closed.