Fix wide-character decoding in URLs.

Author: samth

racket/lib/collects/net/uri-codec.rkt

@@ -167,19 +167,21 @@ See more in PR8831.
 ;; vector string -> string
 (define (decode table str)
   (define max-ascii (integer->char ascii-size))
+  ;; internal-decode : list -> listof[byte]
   (define (internal-decode l)
     (if (null? l) '()
         (let* ([c (car l)] [l (cdr l)]
                [hex (and (equal? #\% c) (pair? l) (pair? (cdr l))
                          (string->number (string (car l) (cadr l)) 16))])
-          (if hex (cons hex (internal-decode (cddr l)))
-              (cons (if (char<? c max-ascii)
-                      (vector-ref table (char->integer c))
-                      ;; This should probably error, but strings to be decoded
-                      ;; might come from misbehaving sources; maybe it's better
-                      ;; to add some parameter for a permissive mode
-                      (bytes->list (string->bytes/utf-8 (string c))))
-                    (internal-decode l))))))
+          (if hex
+              (cons hex (internal-decode (cddr l)))
+              (append (if (char<? c max-ascii)
+                          (list (vector-ref table (char->integer c)))
+                          ;; This should probably error, but strings to be decoded
+                          ;; might come from misbehaving sources; maybe it's better
+                          ;; to add some parameter for a permissive mode
+                          (bytes->list (string->bytes/utf-8 (string c))))
+                      (internal-decode l))))))
   (bytes->string/utf-8 (apply bytes (internal-decode (string->list str)))))
 
 ;; Utility for defining codecs