Fix handling of the ~:(~) directive when the contents are the empty string. Refs #751

Signed-off-by: Stuart Halloway <[email protected]>

Author: tomfaulhaber

src/clj/clojure/pprint/cl_format.clj

@@ -1088,10 +1088,11 @@ Note this should only be used for the last one in the sequence"
             (let [s ^String x]
               (.write writer 
                       ^String (capitalize-string (.toLowerCase s) @last-was-whitespace?))
-              (dosync 
-               (ref-set last-was-whitespace? 
-                        (Character/isWhitespace 
-                         ^Character (nth s (dec (count s)))))))
+              (when (pos? (.length s))
+                (dosync 
+                 (ref-set last-was-whitespace? 
+                          (Character/isWhitespace 
+                           ^Character (nth s (dec (count s))))))))
 
             Integer
             (let [c (char x)]

test/clojure/test_clojure/pprint/test_cl_format.clj

@@ -253,6 +253,8 @@
   (cl-format nil "~:(~A~)" 'kludgy-hash-search) "Kludgy-Hash-Search" 
   (cl-format nil "~:(~A~)" "DON'T!") "Don'T!"     ;not "Don't!" 
   (cl-format nil "~:(~A~)" "pipe 13a, foo16c") "Pipe 13a, Foo16c"
+  (cl-format nil "~:(~A~)" nil) "Nil"
+  (cl-format nil "~:(~A~)" "") ""
 )
 
 (simple-tests square-bracket-tests