Welcome! Please see the About page for a little more info on how this works.

+1 vote
in Printing by

If the format string ends in ~@, there is code in cl-format to detect this
and issue a format-error. However, that error detection is wrong, and a null exception
happens rather than the format-error being reported.

To reproduce this, simply evaluate the following.

clojure.pprint> (cl-format false "~@")
Execution error (NullPointerException) at nrepl.middleware.interruptible-eval/evaluate$fn$fn (interruptible_eval.clj:87).

I have a fix for this which I'd like to contribute.

Here is the new version of the code compile-directive

(defn- compile-directive [s offset]
  (let [[raw-params [rest offset]] (extract-params s offset)
        [_ [rest offset flags]] (extract-flags rest offset)
        directive (first rest)
        ;; previous version was missing (if directive ...) here thus (format-error ...) never reached
        def (if directive (get directive-table (Character/toUpperCase ^Character directive)))
        params (if def (map-params def (map translate-param raw-params) flags offset))]
    (if (not directive)
      (format-error "Format string ended in the middle of a directive" offset))
    (if (not def)
      (format-error (str "Directive \"" directive "\" is undefined") offset))
    [(struct compiled-directive ((:generator-fn def) params offset) def params offset)
     (let [remainder (subs rest 1) 
           offset (inc offset)
           trim? (and (= \newline (:directive def))
                      (not (:colon params)))
           trim-count (if trim? (prefix-count remainder [\space \tab]) 0)
           remainder (subs remainder trim-count)
           offset (+ offset trim-count)]
       [remainder offset])]))

The old version

Please log in or register to answer this question.