*?ex-handler* (clj)



Dynamic var. If non-nil, will be invoked with the exception as argument A one-argument function is excepted. Because `clojure.walk/walk` is used for map traversal, it is not possible to pas s down any argument. Also, as we iteratively walk through nested data structures, some of them do not support metadata. As a result, a binding on this dynamic var in the execution thread enables a simple way to remember the parent value as we visit the children.