select-keys on nil map

Question

I know that https://ask.clojure.org/index.php/1913/use-transients-with-select-keys-if-possible exists to optimize select-keys for many keys, but I noticed that it does a lot of work even if the original map is nil. Would there be interest in a patch that returns an empty map when given nil? Something like:

(defn select-keys*
  "Returns a map containing only those entries in map whose key is in keys"
  {:added "1.0"
   :static true}
  [map keyseq]
  (if map
    (loop [ret {} keys (seq keyseq)]
      (if keys
        (let [entry (. clojure.lang.RT (find map (first keys)))]
          (recur
           (if entry
             (conj ret entry)
             ret)
           (next keys)))
        (with-meta ret (meta map))))
    {}))

Comments

I wonder how often it is called with nil vs an empty map?

Feels to me like this is an edge case that -- if the application code is a hot path when passing nil -- the application code should have the guard on nil.

Otherwise, every user and every call now has to pay the tax of that extra if in all cases.

---

It's no more a tax than any other (when foo ...) call wrapping the body of a nil-punning function.