Critical bug in compare-and-set*

[kwisath]

The compare-and-set* function contains a bug that is hard to spot and can result in a failed compare and set to be compared as successful while it is not.

The problem is with this check

(some? (r/wcar conn
                   (r/multi)
                   (r/set k {:data newval})
                   (r/exec)))

The Carmine return for wcar will always be a vector ["OK" "QUEUED" x] where x is the return of the exec, which in turn would be a vector with the return of all queued transaction operations. If all goes well x will be ["OK"] and if the transaction fails, would be nil. So when the transaction fails, the return is ["OK" "QUEUED" nil], which obviously returns true when passed to some? when it should return false.