ReactMount.nodeCache leaks objects during unmount

[1st1]

The scenario for this is pretty easy to reproduce:

1. Suppose we have a popup implementation -- there is a function to render popup view (react element) in an overlay div element, and a function to unmount the view and destroy the overlay.
2. In that popup we have a button element, with its onClick set to call the destroy popup function.
3. When a user clicks that button, React.unmountComponentAtNode is called, and react cleans everything up (ReactMount.nodeCache is empty), but then, react starts to process the blur event (remember, the user clicked the button to close the popup, so it was focused), and that resurrects the button element in ReactMount.nodeCache.
4. The button DOM element ends up being stuck in nodeCache forever, but the worst part of it is that a lot of DOM nodes (sometimes hundreds) are not subject for GC anymore.

[syranide]

@1st1 If you haven't "figured it out" yet, just defer the unmount and it should all be fine (until this is resolved one way or another).

[1st1]

@syranide I simply "blur()" the button before closing the popup.

The issue though, should be fixed in react. It shouldn't process any events on elements being unmounted, left alone leaving them alive in any caches.

[1st1]

I think this issue is related to #2605

[aweary]

@spicyj this should be closed since 4ba0e95 removed nodeCache, right?

[sophiebits]

Yeah, this should be fixed now. Thank you!