Path: (web uri) - split-and-decode-uri-path must preserve plus characters

[Brent]

Hi all,

Attached is a patch to to correct the behaviour of 
split-and-decode-uri-path in uri.scm from guile 2.0.9.

Fault
-------
The faulty behaviour is:

    (use-modules (web uri))
    (split-and-decode-uri-path "xxx/abc+def/yyy")    → ("xxx" "abc def" 
"yyy")

As can be seen, the plus has been erroneously converted to a space.

The correct behaviour is:

    (split-and-decode-uri-path "xxx/abc+def/yyy")    → ("xxx" "abc+def" 
"yyy")

Analysis
------------
The fault is actually in the uri-decode function invoked by 
split-and-decode-uri-path:
it has special logic to check for a #\+ character and convert it to a space.

The reason for this is that uri-decode is also used to decode query 
string for
application/x-www-form-urlencoded requests where spaces are encoded by 
the client
on submission to plus characters.

(see http://www.w3.org/TR/html401/interact/forms.html#h-17.13.4.1)

Fix
---
The fix is to extend uri-decode with a new keyword argument #:form? that 
is defaulted
to #t. This provides backward compatibility.

split-and-decode-uri-path is modified to call uri-decode with #:form? 
set to #f.

Motivation
---------------
This patch is motivated by the need to embed ISO 8601 timestamps with 
time zones
into URLs:

eg. GET http:/foo.org/aaa/bbb/20140717T072233+0200/xxx/yyy


Please consider this for inclusion.


Thanks,

Brent

--- guile-2.0.9/module/web/uri.scm.orig	2013-03-18 23:30:13.000000000 +0200
+++ guile-2.0.9/module/web/uri.scm	2014-07-15 16:08:47.677521012 +0200
@@ -304,7 +304,7 @@
 (define hex-chars
   (string->char-set "0123456789abcdefABCDEF"))
 
-(define* (uri-decode str #:key (encoding "utf-8"))
+(define* (uri-decode str #:key (encoding "utf-8") (form? #t))
   "Percent-decode the given STR, according to ENCODING,
 which should be the name of a character encoding.
 
@@ -330,7 +330,7 @@
                (if (< i len)
                    (let ((ch (string-ref str i)))
                      (cond
-                      ((eqv? ch #\+)
+                      ((and (eqv? ch #\+) form?)
                        (put-u8 port (char->integer #\space))
                        (lp (1+ i)))
                       ((and (< (+ i 2) len) (eqv? ch #\%)
@@ -412,7 +412,8 @@
 For example, ‘\"/foo/bar%20baz/\"’ decodes to the two-element list,
 ‘(\"foo\" \"bar baz\")’."
   (filter (lambda (x) (not (string-null? x)))
-          (map uri-decode (string-split path #\/))))
+          (map (lambda (s) (uri-decode s #:form? #f))
+               (string-split path #\/))))
 
 (define (encode-and-join-uri-path parts)
   "URI-encode each element of PARTS, which should be a list of