In ClojureScript, using ns-unmap on a symbol from cljs.core doesn't exclude it from the current namespace. Note that both a function and a macro still exist, even after unmapping:
This differs from the behavior of Clojure's ns-unmap. Note the appropriate errors when attempting to use unmapped symbols:
Somehow ClojureScript's ns-unmap needs to add the symbol to the current namespace's :excludes set. Note that the def special form does this already (after it displays a warning).
We have two solutions. 0001 extends the ns form's :merge behavior to support :excludes, and then uses this in ns-unmap. If the enhancement to ns isn't wanted, patch 0002 changes ns-unmap to update :excludes directly.
The second patch is preferred. However it seems the second patch is too permissive. The :excludes logic should only be applied if the symbol identifies a core macro or fn.
The ns form's own :refer-clojure :exclude accepts arbitrary symbols and adds them to the namespace's :excludes set, which seems like the same permissiveness problem. Do you want a patch that addresses the permissiveness of both ns and ns-unmap in this ticket, or should such a patch go in a new ticket?
New ticket to fix the bug that :exclude doesn't check the symbol list for cljs.core declared vars, and an updated patch here please.