The new ChangeApplier fixes bugs wrt use of arrays as paths, but will fail if a circularly-linked object is applied to the model since the "diff" algorithm will run away attempting to assess the change. This arose in the context of trying to insert socket.io socket objects into a model for the GPII's "browserChannel" implementation - see discussion in IRC at https://botbot.me/freenode/fluid-work/2015-06-15/?msg=41926924&page=1

Whilst we don't currently support this form of model contents (although we may be able to in future, in conjunction with the "immutable application" model described at https://wiki.fluidproject.org/display/fluid/New+New+Notes+on+the+ChangeApplier ), we should at least supply a sensible diagnostic in this case. We should also as another line of safety have fluid.model.applyChangeStrategy bail out on any kind of exotic object (it's probable that the https://fluidproject.atlassian.net/browse/FLUID-5249#icft=FLUID-5249 branch already achieves this as a result of improvements to fluid.isPlainObject).