Disabling a child in a script while its parent is being disabled is broken

This is the current enabled property setter on an Entity:

if (this._enabled !== enabled) {
  this._enabled = enabled;

  if (! this._parent || this._parent.enabled)
    this._notifyHierarchyStateChanged(this, enabled);
}

When _notifyHierarchyStateChanged is called it will fire the disable event handler on scripts. If a script tries to disable a child Entity during this event, then the children of that Entity will not be disabled because this._parent._enabled is false. But the parent has not finished disabling itself yet.

Start with the Entity enabled property setter and _notifyHierarchyStateChanged, then reproduce a parent-disable event whose script disables a child. Trace the hierarchy state propagation and verify that the child and its descendants are disabled before considering the issue resolved.