Async onEnter hook can lead to inconsistent state

[hoschi]

Version

2.4.0

Test Case

http://codepen.io/hoschi/pen/wGbZWo?editors=0010

Steps to reproduce

• click on "Users" link, shows still "Home"
• click on "Widgets" link, shows Widgets component
• wait

Expected Behavior

• Widgets component stays visible
• url is still "/widgets"

Actual Behavior

• Users component shows up
• url is still "/widgets", which doesn't match the component on the screen

Description

The example has an onEnter hook which calls the callback after two seconds. When you move away from the "Users" route to "Widgets" all works fine. After the delay finishes you get an inconsistent state, as described above.

I think the problem lies in async management of hooks, where waiting callbacks should be dismissed on a location change.

[alisd23]

Should be fixed in #4063