Summary: This invariant is unnecessary because `ReactComponent.Mixin.receiveProps` already asserts that this component is mounted. (Being mounted guarantees you have a DOM ID, look at `ReactComponent` and see when `this._rootNodeID` is mutated.)
This fixes an edge case that can cause unnecessary mutations in the DOM. Namely, if a prop is falsey, it will get touched on every update by reconciliation. See unit test.
This cleans up the reconcilation path when adding a `style` prop (going from a falsey or no `style` to having one) by reducing the need for an object allocation and for-loop.
The most obvious manifestation of this bug is visible here:
http://jsfiddle.net/spicyj/zzGas/. In short, when props are removed from a
component, the underlying HTML element doesn't have the attribute
removed.
This change should fix it, but unfortunately it (presumably) makes
_updateDOMProperties a bit slower.
ReactEvent should be reserved for the actual object created when an
event fires. The current ReactEvent is more like EventEmitter than
anything (e.g. it sets up delegation, provides methods to attach and
remove listeners).
We need to make sure that deleteAllListeners() is invoked before we call
the superclass's unmountComponent() method or else we will lose
this._rootNodeID.
I also added an invariant and unit test to make sure we do not break
this in the future.
CommitSyncScript
Ben Alpert
Paul O’Shannessy