From 86572cc8c33ba12482043718d16225806c7601f5 Mon Sep 17 00:00:00 2001
From: Robby Findler <robby@racket-lang.org>
Date: Thu, 29 Mar 2012 17:22:49 -0500
Subject: [PATCH] adjust the contract on string->url so that it actually
 catches all of the errors that would be signalled by the body. also, remove
 url-regexp from the exports (it was only recently added)

I believe this eliminates two of Eli's concerns:

  - the contract is no longer so painful to read

  - the performance is more reasonable.

Specifically, for the performance, here are the times I see to call
string->url on "http://www.racket-lang.org":

no contract: any/c
cpu time: 564 real time: 566 gc time: 3

weak contract: (-> (or/c string? bytes?) url?)
cpu time: 590 real time: 590 gc time: 3

strong, regexp-based contract:
(-> (or/c (not/c #rx"^([^:/?#]*):") #rx"^[a-zA-Z][a-zA-Z0-9+.-]*:") url?)
cpu time: 632 real time: 633 gc time: 5

This appears to be about a 10% slowdown for the regexp-based contract
over the weaker contract.

related to PR 12652
---
 collects/net/scribblings/url.scrbl | 20 +++++++-------------
 collects/net/url.rkt               |  5 +++--
 2 files changed, 10 insertions(+), 15 deletions(-)

diff --git a/collects/net/scribblings/url.scrbl b/collects/net/scribblings/url.scrbl
index 2d04a7dc43..4c7297efbf 100644
--- a/collects/net/scribblings/url.scrbl
+++ b/collects/net/scribblings/url.scrbl
@@ -1,6 +1,5 @@
 #lang scribble/doc
 @(require "common.rkt" scribble/bnf
-          (only-in net/url url-regexp)
           (for-label net/url net/url-unit net/url-sig 
                      net/head net/uri-codec net/tcp-sig
                      (only-in net/url-connect current-https-protocol)
@@ -96,7 +95,9 @@ An HTTP connection is created as a @deftech{pure port} or a
 have been removed, so that what remains is purely the first content
 fragment. An impure port is one that still has its MIME headers.
 
-@defproc[(string->url [str (and/c (or/c string? bytes?) url-regexp)]) url?]{
+@defproc[(string->url [str (or/c (not/c #rx"^([^:/?#]*):")
+                                 #rx"^[a-zA-Z][a-zA-Z0-9+.-]*:")])
+         url?]{
 
 Parses the URL specified by @racket[str] into a @racket[url]
 struct. The @racket[string->url] procedure uses
@@ -104,6 +105,10 @@ struct. The @racket[string->url] procedure uses
 sensitive to the @racket[current-alist-separator-mode] parameter for
 determining the association separator.
 
+The contract on @racket[str] insists that, if the url has a scheme,
+then the scheme begins with a letter and consists only of letters,
+numbers, @litchar{+}, @litchar{-}, and @litchar{.} characters.
+
 If @racket[str] starts with @racket["file:"], then the path is always
 parsed as an absolute path, and the parsing details depend on
 @racket[file-url-path-convention-type]:
@@ -123,17 +128,6 @@ parsed as an absolute path, and the parsing details depend on
 
 ]}
 
-@defthing[url-regexp regexp?]{
-
-This is a regular expression based on the one in
-Appendix B of RFC 3986 for recognizing urls.
-
-This is the precise regexp:
-
-@centered{@tt{@(object-name url-regexp)}}
-                              
-}
-
 @defproc[(combine-url/relative [base url?] [relative string?]) url?]{
 
 Given a base URL and a relative path, combines the two and returns a
diff --git a/collects/net/url.rkt b/collects/net/url.rkt
index b55dbda5b1..6abbbe000d 100644
--- a/collects/net/url.rkt
+++ b/collects/net/url.rkt
@@ -660,8 +660,9 @@
 (provide (struct-out url) (struct-out path/param))
 
 (provide/contract
- [url-regexp regexp?]
- (string->url (url-regexp . -> . url?))
+ (string->url (-> (or/c #rx"^[a-zA-Z][a-zA-Z0-9+.-]*:"
+                        (not/c #rx"^([^:/?#]*):"))
+                  url?))
  (path->url ((or/c path-string? path-for-some-system?) . -> . url?))
  (url->string (url? . -> . string?))
  (url->path (->* (url?) ((one-of/c 'unix 'windows)) path-for-some-system?))