1.0 ng1: Hooks can still be called after de-register invocation

[jgrund]

We are seeing a case where our hook callback is invoked after de-registering it.

It seems that the callback should never be invoked after a de-register is called.

[johnsonw]

👍 , seeing the same thing.

[christopherthielen]

Are you deregistering the hook while a transition is in process? The hook pipeline is computed when the transition starts.

What is your use case(s)?

[jgrund]

So the basic scenario can be boiled down to:

   // factory
   function serviceWithTransitions ($transitions) {
     return () => 
       $transitions.onSuccess({}, console.log);
   };

  const component = {
    controller: function (serviceWithTransition) {
      this.$onDestroy = serviceWithTransition();
    },
    template: '<foo></foo>'
  }

Where component is registered as a component on a state.

What ends up happening is:

1. $onDestroy is invoked on a route transition.
2. The onSuccess handler is de-registered.
3. The onSuccess handler fires for the component being navigated away from, even though it was de-registered previously.

What I considered surprising about this is that invoking the de-registration function is not upheld 100 percent of the time.

It seems like this can lead to subtle bugs as I suspect others with have the same assumption.

[christopherthielen]

I see... that's helpful, thanks for the use case details.

I agree that's surprising behavior as you described.

---

Here's the details of why it's happening:

1. Transition to first state
2. Component is created, hook is registered in global registry
3. Transition away from first state

• onBefore hooks are fetched and sorted by priority, then run in order
• all matching (async) hooks are fetched from global registry
• those hooks are and sorted by hook type/hook priority, then queued for run in order
• Transition is successful.

4. onSuccess hooks are fetched and sorted by priority

• your onSuccess hook is placed in the onSuccess pipeline at this time
• Views are updated
  • The component is destroyed, hook deregister function is invoked. Hook is removed from global registry.
  • The pipeline is already computed, so is unaffected

---

I'm going to have to give some thought to this.

[christopherthielen]

Fixed by #2939