commit 81f61a615ff8c5c5d6e270c255c15eb164f3456c
Author: Andy Wingo <wingo@pobox.com>
Date:   Wed Oct 15 11:49:41 2014 +0200

    web: Location header is URI-reference; better URI-reference support
    
    * module/web/uri.scm (validate-uri): Add reference? keyword argument,
      for validating references.
      (build-uri): Clarify comments to indicate that the result is an
      absolute URI.
      (build-uri-reference): New interface, to build URI-references.
      (string->uri-reference): Rename from string->uri*.  Fix fragment
      parsing to not include the #.
      (string->uri): Adapt to string->uri-reference name change.
    
    * module/web/request.scm (request-absolute-uri): Add default-scheme
      optional argument.  Use it if the request-uri has no scheme, or
      error.
    
    * module/web/http.scm (write-uri): Reflow to use "when".  Fix writing of
      URI-reference instances.
      (declare-uri-reference-header!): Rename from
      declare-relative-uri-header!.  Use string->uri-reference.
      ("Location"): Declare as a URI-reference header, as per RFC 7231.
    
    * module/web/client.scm (open-socket-for-uri): Handle the case in which
      there is no URI scheme.
    
    * test-suite/tests/web-http.test:
    * test-suite/tests/web-uri.test: Add tests.

diff --git a/module/web/client.scm b/module/web/client.scm
index 3f6c45b..ef2314b 100644
--- a/module/web/client.scm
+++ b/module/web/client.scm
@@ -1,6 +1,6 @@
 ;;; Web client
 
-;; Copyright (C) 2011, 2012, 2013 Free Software Foundation, Inc.
+;; Copyright (C) 2011, 2012, 2013, 2014 Free Software Foundation, Inc.
 
 ;; This library is free software; you can redistribute it and/or
 ;; modify it under the terms of the GNU Lesser General Public
@@ -74,7 +74,8 @@
       (delete-duplicates
        (getaddrinfo (uri-host uri)
                     (cond (port => number->string)
-                          (else (symbol->string (uri-scheme uri))))
+                          ((uri-scheme uri) => symbol->string)
+                          (else (error "Not an absolute URI" uri)))
                     (if port
                         AI_NUMERICSERV
                         0))
diff --git a/module/web/http.scm b/module/web/http.scm
index aa75142..a157cf0 100644
--- a/module/web/http.scm
+++ b/module/web/http.scm
@@ -1090,20 +1090,19 @@ three values: the method, the URI, and the version."
         (bad-request "Bad Request-Line: ~s" line))))
 
 (define (write-uri uri port)
-  (if (uri-host uri)
-      (begin
-        (display (uri-scheme uri) port)
-        (display "://" port)
-        (if (uri-userinfo uri)
-            (begin
-              (display (uri-userinfo uri) port)
-              (display #\@ port)))
-        (display (uri-host uri) port)
-        (let ((p (uri-port uri)))
-          (if (and p (not (eqv? p 80)))
-              (begin
-                (display #\: port)
-                (display p port))))))
+  (when (uri-host uri)
+    (when (uri-scheme uri)
+      (display (uri-scheme uri) port)
+      (display #\: port))
+    (display "//" port)
+    (when (uri-userinfo uri)
+      (display (uri-userinfo uri) port)
+      (display #\@ port))
+    (display (uri-host uri) port)
+    (let ((p (uri-port uri)))
+      (when (and p (not (eqv? p 80)))
+        (display #\: port)
+        (display p port))))
   (let* ((path (uri-path uri))
          (len (string-length path)))
     (cond
@@ -1113,10 +1112,9 @@ three values: the method, the URI, and the version."
       (bad-request "Empty path and no host for URI: ~s" uri))
      (else
       (display path port))))
-  (if (uri-query uri)
-      (begin
-        (display #\? port)
-        (display (uri-query uri) port))))
+  (when (uri-query uri)
+    (display #\? port)
+    (display (uri-query uri) port)))
 
 (define (write-request-line method uri version port)
   "Write the first line of an HTTP request to PORT."
@@ -1226,11 +1224,11 @@ treated specially, and is just returned as a plain string."
     (@@ (web uri) absolute-uri?)
     write-uri))
 
-;; emacs: (put 'declare-relative-uri-header! 'scheme-indent-function 1)
-(define (declare-relative-uri-header! name)
+;; emacs: (put 'declare-uri-reference-header! 'scheme-indent-function 1)
+(define (declare-uri-reference-header! name)
   (declare-header! name
     (lambda (str)
-      (or ((@@ (web uri) string->uri*) str)
+      (or (string->uri-reference str)
           (bad-header-component 'uri str)))
     uri?
     write-uri))
@@ -1519,9 +1517,9 @@ treated specially, and is just returned as a plain string."
 ;;
 (declare-integer-header! "Content-Length")
 
-;; Content-Location = ( absoluteURI | relativeURI )
+;; Content-Location = URI-reference
 ;;
-(declare-relative-uri-header! "Content-Location")
+(declare-uri-reference-header! "Content-Location")
 
 ;; Content-MD5 = <base64 of 128 bit MD5 digest as per RFC 1864>
 ;;
@@ -1822,9 +1820,9 @@ treated specially, and is just returned as a plain string."
            (display (cdr pair) port)))
      ",")))
 
-;; Referer = ( absoluteURI | relativeURI )
+;; Referer = URI-reference
 ;;
-(declare-relative-uri-header! "Referer")
+(declare-uri-reference-header! "Referer")
 
 ;; TE = #( t-codings )
 ;; t-codings = "trailers" | ( transfer-extension [ accept-params ] )
@@ -1859,9 +1857,13 @@ treated specially, and is just returned as a plain string."
   entity-tag?
   write-entity-tag)
 
-;; Location = absoluteURI
+;; Location = URI-reference
+;;
+;; In RFC 2616, Location was specified as being an absolute URI.  This
+;; was changed in RFC 7231 to permit URI references generally, which
+;; matches web reality.
 ;; 
-(declare-uri-header! "Location")
+(declare-uri-reference-header! "Location")
 
 ;; Proxy-Authenticate = 1#challenge
 ;;
diff --git a/module/web/request.scm b/module/web/request.scm
index 7ced076..0a206cf 100644
--- a/module/web/request.scm
+++ b/module/web/request.scm
@@ -300,7 +300,8 @@ request R."
 (define-request-accessor user-agent #f)
 
 ;; Misc accessors
-(define* (request-absolute-uri r #:optional default-host default-port)
+(define* (request-absolute-uri r #:optional default-host default-port
+                               default-scheme)
   "A helper routine to determine the absolute URI of a request, using the
 ‘host’ header and the default host and port."
   (let ((uri (request-uri r)))
@@ -313,7 +314,10 @@ request R."
                        (bad-request
                         "URI not absolute, no Host header, and no default: ~s"
                         uri)))))
-          (build-uri (uri-scheme uri)
+          (build-uri (or (uri-scheme uri)
+                         default-scheme
+                         (bad-request "URI not absolute and no default-port"
+                                      uri))
                      #:host (car host)
                      #:port (cdr host)
                      #:path (uri-path uri)
diff --git a/module/web/uri.scm b/module/web/uri.scm
index 3ab820d..063d7ee 100644
--- a/module/web/uri.scm
+++ b/module/web/uri.scm
@@ -36,8 +36,10 @@
             uri-path uri-query uri-fragment
 
             build-uri
+            build-uri-reference
             declare-default-port!
-            string->uri uri->string
+            string->uri string->uri-reference
+            uri->string
             uri-decode uri-encode
             split-and-decode-uri-path
             encode-and-join-uri-path))
@@ -62,9 +64,10 @@
 (define (positive-exact-integer? port)
   (and (number? port) (exact? port) (integer? port) (positive? port)))
 
-(define (validate-uri scheme userinfo host port path query fragment)
+(define* (validate-uri scheme userinfo host port path query fragment
+                       #:key reference?)
   (cond
-   ((not (symbol? scheme))
+   ((and (not reference?) (not (symbol? scheme)))
     (uri-error "Expected a symbol for the URI scheme: ~s" scheme))
    ((and (or userinfo port) (not host))
     (uri-error "Expected a host, given userinfo or port"))
@@ -82,15 +85,26 @@
 
 (define* (build-uri scheme #:key userinfo host port (path "") query fragment
                     (validate? #t))
-  "Construct a URI object.  SCHEME should be a symbol, PORT
-either a positive, exact integer or ‘#f’, and the rest of the
-fields are either strings or ‘#f’.  If VALIDATE? is true,
-also run some consistency checks to make sure that the constructed URI
-is valid."
+  "Construct a URI object.  SCHEME should be a symbol, PORT either a
+positive, exact integer or ‘#f’, and the rest of the fields are either
+strings or ‘#f’.  If VALIDATE? is true, also run some consistency checks
+to make sure that the constructed object is a valid absolute URI."
   (if validate?
       (validate-uri scheme userinfo host port path query fragment))
   (make-uri scheme userinfo host port path query fragment))
 
+(define* (build-uri-reference #:key scheme userinfo host port (path "") query
+                              fragment (validate? #t))
+  "Construct a URI object.  SCHEME should be a symbol or ‘#f’, PORT
+either a positive, exact integer or ‘#f’, and the rest obf the fields
+are either strings or ‘#f’.  If VALIDATE? is true, also run some
+consistency checks to make sure that the constructed URI is a valid URI
+reference (either an absolute URI or a relative reference)."
+  (if validate?
+      (validate-uri scheme userinfo host port path query fragment
+                    #:reference? #t))
+  (make-uri scheme userinfo host port path query fragment))
+
 ;; See RFC 3986 #3.2.2 for comments on percent-encodings, IDNA (RFC
 ;; 3490), and non-ASCII host names.
 ;;
@@ -156,6 +170,10 @@ is valid."
 ;;;               / path-absolute
 ;;;               / path-rootless
 ;;;               / path-empty
+;;;
+;;;   A URI-reference is the same as URI, but where the scheme is
+;;;   optional.  If the scheme is not present, its colon isn't present
+;;;   either.
 
 (define scheme-pat
   "[a-zA-Z][a-zA-Z0-9+.-]*")
@@ -173,9 +191,9 @@ is valid."
 (define uri-regexp
   (make-regexp uri-pat))
 
-(define (string->uri* string)
-  "Parse STRING into a URI object.  Return ‘#f’ if the string
-could not be parsed."
+(define (string->uri-reference string)
+  "Parse the URI reference written as STRING into a URI object.  Return
+‘#f’ if the string could not be parsed."
   (% (let ((m (regexp-exec uri-regexp string)))
        (if (not m) (abort))
        (let ((scheme (let ((str (match:substring m 2)))
@@ -183,7 +201,7 @@ could not be parsed."
              (authority (match:substring m 3))
              (path (match:substring m 4))
              (query (match:substring m 6))
-             (fragment (match:substring m 7)))
+             (fragment (match:substring m 8)))
          (call-with-values
              (lambda ()
                (if authority
@@ -195,9 +213,9 @@ could not be parsed."
        #f)))
 
 (define (string->uri string)
-  "Parse STRING into a URI object.  Return ‘#f’ if the string
+  "Parse STRING into an absolute URI object.  Return ‘#f’ if the string
 could not be parsed."
-  (let ((uri (string->uri* string)))
+  (let ((uri (string->uri-reference string)))
     (and uri (uri-scheme uri) uri)))
 
 (define *default-ports* (make-hash-table))
diff --git a/test-suite/tests/web-http.test b/test-suite/tests/web-http.test
index 45cce02..dfc9677 100644
--- a/test-suite/tests/web-http.test
+++ b/test-suite/tests/web-http.test
@@ -345,6 +345,14 @@
   (pass-if-parse etag "W/\"foo\"" '("foo" . #f))
   (pass-if-parse location "http://other-place"
                  (build-uri 'http #:host "other-place"))
+  (pass-if-parse location "#foo"
+                 (build-uri-reference #:fragment "foo"))
+  (pass-if-parse location "/#foo"
+                 (build-uri-reference #:path "/" #:fragment "foo"))
+  (pass-if-parse location "/foo"
+                 (build-uri-reference #:path "/foo"))
+  (pass-if-parse location "//server/foo"
+                 (build-uri-reference #:host "server" #:path "/foo"))
   (pass-if-parse proxy-authenticate "Basic realm=\"guile\""
                  '((basic (realm . "guile"))))
   (pass-if-parse retry-after "Tue, 15 Nov 1994 08:12:31 GMT"
diff --git a/test-suite/tests/web-uri.test b/test-suite/tests/web-uri.test
index 3d14d9d..4873d7f 100644
--- a/test-suite/tests/web-uri.test
+++ b/test-suite/tests/web-uri.test
@@ -1,6 +1,6 @@
 ;;;; web-uri.test --- URI library          -*- mode: scheme; coding: utf-8; -*-
 ;;;;
-;;;; 	Copyright (C) 2010, 2011, 2012 Free Software Foundation, Inc.
+;;;; 	Copyright (C) 2010, 2011, 2012, 2014 Free Software Foundation, Inc.
 ;;;;
 ;;;; This library is free software; you can redistribute it and/or
 ;;;; modify it under the terms of the GNU Lesser General Public
@@ -210,7 +210,298 @@
   (pass-if "file:///etc/hosts"
     (uri=? (string->uri "file:///etc/hosts")
            #:scheme 'file
-           #:path "/etc/hosts")))
+           #:path "/etc/hosts"))
+
+  (pass-if "http://foo#bar"
+    (uri=? (string->uri "http://foo#bar")
+           #:scheme 'http
+           #:host "foo"
+           #:path ""
+           #:fragment "bar"))
+
+  (pass-if "http://foo:/#bar"
+    (uri=? (string->uri "http://foo:/#bar")
+           #:scheme 'http
+           #:host "foo"
+           #:path "/"
+           #:fragment "bar"))
+
+  (pass-if "http://foo:100#bar"
+    (uri=? (string->uri "http://foo:100#bar")
+           #:scheme 'http
+           #:host "foo"
+           #:port 100
+           #:path ""
+           #:fragment "bar"))
+
+  (pass-if "http://foo:100/#bar"
+    (uri=? (string->uri "http://foo:100/#bar")
+           #:scheme 'http
+           #:host "foo"
+           #:port 100
+           #:path "/"
+           #:fragment "bar"))
+
+  (pass-if "http://foo?q#bar"
+    (uri=? (string->uri "http://foo?q#bar")
+           #:scheme 'http
+           #:host "foo"
+           #:path ""
+           #:query "q"
+           #:fragment "bar"))
+
+  (pass-if "http://foo:/?q#bar"
+    (uri=? (string->uri "http://foo:/?q#bar")
+           #:scheme 'http
+           #:host "foo"
+           #:path "/"
+           #:query "q"
+           #:fragment "bar"))
+
+  (pass-if "http://foo:100?q#bar"
+    (uri=? (string->uri "http://foo:100?q#bar")
+           #:scheme 'http
+           #:host "foo"
+           #:port 100
+           #:path ""
+           #:query "q"
+           #:fragment "bar"))
+
+  (pass-if "http://foo:100/?q#bar"
+    (uri=? (string->uri "http://foo:100/?q#bar")
+           #:scheme 'http
+           #:host "foo"
+           #:port 100
+           #:path "/"
+           #:query "q"
+           #:fragment "bar")))
+
+(with-test-prefix "string->uri-reference"
+  (pass-if "/foo"
+    (uri=? (string->uri-reference "/foo")
+           #:path "/foo"))
+  
+  (pass-if "ftp:/foo"
+    (uri=? (string->uri-reference "ftp:/foo")
+           #:scheme 'ftp
+           #:path "/foo"))
+  
+  (pass-if "ftp:foo"
+    (uri=? (string->uri-reference "ftp:foo")
+           #:scheme 'ftp
+           #:path "foo"))
+  
+  (pass-if "//foo/bar"
+    (uri=? (string->uri-reference "//foo/bar")
+           #:host "foo"
+           #:path "/bar"))
+  
+  (pass-if "ftp://foo@bar:22/baz"
+    (uri=? (string->uri-reference "ftp://foo@bar:22/baz")
+           #:scheme 'ftp
+           #:userinfo "foo"
+           #:host "bar"
+           #:port 22
+           #:path "/baz"))
+
+  (pass-if "//foo@bar:22/baz"
+    (uri=? (string->uri-reference "//foo@bar:22/baz")
+           #:userinfo "foo"
+           #:host "bar"
+           #:port 22
+           #:path "/baz"))
+
+  (pass-if "http://bad.host.1"
+    (not (string->uri-reference "http://bad.host.1")))
+
+  (pass-if "//bad.host.1"
+    (not (string->uri-reference "//bad.host.1")))
+
+  (pass-if "http://1.good.host"
+    (uri=? (string->uri-reference "http://1.good.host")
+           #:scheme 'http #:host "1.good.host" #:path ""))
+
+  (pass-if "//1.good.host"
+    (uri=? (string->uri-reference "//1.good.host")
+           #:host "1.good.host" #:path ""))
+
+  (when (memq 'socket *features*)
+    (pass-if "http://192.0.2.1"
+      (uri=? (string->uri-reference "http://192.0.2.1")
+             #:scheme 'http #:host "192.0.2.1" #:path ""))
+
+    (pass-if "//192.0.2.1"
+      (uri=? (string->uri-reference "//192.0.2.1")
+             #:host "192.0.2.1" #:path ""))
+
+    (pass-if "http://[2001:db8::1]"
+      (uri=? (string->uri-reference "http://[2001:db8::1]")
+             #:scheme 'http #:host "2001:db8::1" #:path ""))
+
+    (pass-if "//[2001:db8::1]"
+      (uri=? (string->uri-reference "//[2001:db8::1]")
+             #:host "2001:db8::1" #:path ""))
+
+    (pass-if "http://[2001:db8::1]:80"
+      (uri=? (string->uri-reference "http://[2001:db8::1]:80")
+             #:scheme 'http
+             #:host "2001:db8::1"
+             #:port 80
+             #:path ""))
+
+    (pass-if "//[2001:db8::1]:80"
+      (uri=? (string->uri-reference "//[2001:db8::1]:80")
+             #:host "2001:db8::1"
+             #:port 80
+             #:path ""))
+
+    (pass-if "http://[::ffff:192.0.2.1]"
+      (uri=? (string->uri-reference "http://[::ffff:192.0.2.1]")
+             #:scheme 'http #:host "::ffff:192.0.2.1" #:path ""))
+
+    (pass-if "//[::ffff:192.0.2.1]"
+      (uri=? (string->uri-reference "//[::ffff:192.0.2.1]")
+             #:host "::ffff:192.0.2.1" #:path "")))
+
+  (pass-if "http://foo:"
+    (uri=? (string->uri-reference "http://foo:")
+           #:scheme 'http #:host "foo" #:path ""))
+
+  (pass-if "//foo:"
+    (uri=? (string->uri-reference "//foo:")
+           #:host "foo" #:path ""))
+
+  (pass-if "http://foo:/"
+    (uri=? (string->uri-reference "http://foo:/")
+           #:scheme 'http #:host "foo" #:path "/"))
+
+  (pass-if "//foo:/"
+    (uri=? (string->uri-reference "//foo:/")
+           #:host "foo" #:path "/"))
+
+  (pass-if "http://2012.jsconf.us/"
+    (uri=? (string->uri-reference "http://2012.jsconf.us/")
+           #:scheme 'http #:host "2012.jsconf.us" #:path "/"))
+
+  (pass-if "//2012.jsconf.us/"
+    (uri=? (string->uri-reference "//2012.jsconf.us/")
+           #:host "2012.jsconf.us" #:path "/"))
+
+  (pass-if "http://foo:not-a-port"
+    (not (string->uri-reference "http://foo:not-a-port")))
+  
+  (pass-if "//foo:not-a-port"
+    (not (string->uri-reference "//foo:not-a-port")))
+  
+  (pass-if "http://:10"
+    (not (string->uri-reference "http://:10")))
+
+  (pass-if "//:10"
+    (not (string->uri-reference "//:10")))
+
+  (pass-if "http://foo@"
+    (not (string->uri-reference "http://foo@")))
+
+  (pass-if "//foo@"
+    (not (string->uri-reference "//foo@")))
+
+  (pass-if "file:/"
+    (uri=? (string->uri-reference "file:/")
+           #:scheme 'file
+           #:path "/"))
+
+  (pass-if "/"
+    (uri=? (string->uri-reference "/")
+           #:path "/"))
+
+  (pass-if "foo"
+    (uri=? (string->uri-reference "foo")
+           #:path "foo"))
+
+  (pass-if "file:/etc/hosts"
+    (uri=? (string->uri-reference "file:/etc/hosts")
+           #:scheme 'file
+           #:path "/etc/hosts"))
+
+  (pass-if "/etc/hosts"
+    (uri=? (string->uri-reference "/etc/hosts")
+           #:path "/etc/hosts"))
+
+  (pass-if "file:///etc/hosts"
+    (uri=? (string->uri-reference "file:///etc/hosts")
+           #:scheme 'file
+           #:path "/etc/hosts"))
+
+  (pass-if "///etc/hosts"
+    (uri=? (string->uri-reference "///etc/hosts")
+           #:path "/etc/hosts"))
+
+  (pass-if "/foo#bar"
+    (uri=? (string->uri-reference "/foo#bar")
+           #:path "/foo"
+           #:fragment "bar"))
+
+  (pass-if "//foo#bar"
+    (uri=? (string->uri-reference "//foo#bar")
+           #:host "foo"
+           #:path ""
+           #:fragment "bar"))
+
+  (pass-if "//foo:/#bar"
+    (uri=? (string->uri-reference "//foo:/#bar")
+           #:host "foo"
+           #:path "/"
+           #:fragment "bar"))
+
+  (pass-if "//foo:100#bar"
+    (uri=? (string->uri-reference "//foo:100#bar")
+           #:host "foo"
+           #:port 100
+           #:path ""
+           #:fragment "bar"))
+
+  (pass-if "//foo:100/#bar"
+    (uri=? (string->uri-reference "//foo:100/#bar")
+           #:host "foo"
+           #:port 100
+           #:path "/"
+           #:fragment "bar"))
+
+  (pass-if "/foo?q#bar"
+    (uri=? (string->uri-reference "/foo?q#bar")
+           #:path "/foo"
+           #:query "q"
+           #:fragment "bar"))
+
+  (pass-if "//foo?q#bar"
+    (uri=? (string->uri-reference "//foo?q#bar")
+           #:host "foo"
+           #:path ""
+           #:query "q"
+           #:fragment "bar"))
+
+  (pass-if "//foo:/?q#bar"
+    (uri=? (string->uri-reference "//foo:/?q#bar")
+           #:host "foo"
+           #:path "/"
+           #:query "q"
+           #:fragment "bar"))
+
+  (pass-if "//foo:100?q#bar"
+    (uri=? (string->uri-reference "//foo:100?q#bar")
+           #:host "foo"
+           #:port 100
+           #:path ""
+           #:query "q"
+           #:fragment "bar"))
+
+  (pass-if "//foo:100/?q#bar"
+    (uri=? (string->uri-reference "//foo:100/?q#bar")
+           #:host "foo"
+           #:port 100
+           #:path "/"
+           #:query "q"
+           #:fragment "bar")))
 
 (with-test-prefix "uri->string"
   (pass-if "ftp:"
@@ -225,30 +516,78 @@
     (equal? "ftp://foo/bar"
             (uri->string (string->uri "ftp://foo/bar"))))
   
+  (pass-if "//foo/bar"
+    (equal? "//foo/bar"
+            (uri->string (string->uri-reference "//foo/bar"))))
+  
   (pass-if "ftp://foo@bar:22/baz"
     (equal? "ftp://foo@bar:22/baz"
             (uri->string (string->uri "ftp://foo@bar:22/baz"))))
   
+  (pass-if "//foo@bar:22/baz"
+    (equal? "//foo@bar:22/baz"
+            (uri->string (string->uri-reference "//foo@bar:22/baz"))))
+  
   (when (memq 'socket *features*)
     (pass-if "http://192.0.2.1"
       (equal? "http://192.0.2.1"
               (uri->string (string->uri "http://192.0.2.1"))))
 
+    (pass-if "//192.0.2.1"
+      (equal? "//192.0.2.1"
+              (uri->string (string->uri-reference "//192.0.2.1"))))
+
     (pass-if "http://[2001:db8::1]"
       (equal? "http://[2001:db8::1]"
               (uri->string (string->uri "http://[2001:db8::1]"))))
 
+    (pass-if "//[2001:db8::1]"
+      (equal? "//[2001:db8::1]"
+              (uri->string (string->uri-reference "//[2001:db8::1]"))))
+
     (pass-if "http://[::ffff:192.0.2.1]"
       (equal? "http://[::ffff:192.0.2.1]"
-              (uri->string (string->uri "http://[::ffff:192.0.2.1]")))))
+              (uri->string (string->uri "http://[::ffff:192.0.2.1]"))))
+
+    (pass-if "//[::ffff:192.0.2.1]"
+      (equal? "//[::ffff:192.0.2.1]"
+              (uri->string (string->uri-reference "//[::ffff:192.0.2.1]")))))
 
   (pass-if "http://foo:"
     (equal? "http://foo"
             (uri->string (string->uri "http://foo:"))))
   
+  (pass-if "//foo"
+    (equal? "//foo"
+            (uri->string (string->uri-reference "//foo"))))
+
   (pass-if "http://foo:/"
     (equal? "http://foo/"
-            (uri->string (string->uri "http://foo:/")))))
+            (uri->string (string->uri "http://foo:/"))))
+
+  (pass-if "//foo:/"
+    (equal? "//foo/"
+            (uri->string (string->uri-reference "//foo:/"))))
+
+  (pass-if "/"
+    (equal? "/"
+            (uri->string (string->uri-reference "/"))))
+
+  (pass-if "/foo"
+    (equal? "/foo"
+            (uri->string (string->uri-reference "/foo"))))
+
+  (pass-if "/foo/"
+    (equal? "/foo/"
+            (uri->string (string->uri-reference "/foo/"))))
+
+  (pass-if "/foo/?bar#baz"
+    (equal? "/foo/?bar#baz"
+            (uri->string (string->uri-reference "/foo/?bar#baz"))))
+
+  (pass-if "foo/?bar#baz"
+    (equal? "foo/?bar#baz"
+            (uri->string (string->uri-reference "foo/?bar#baz")))))
 
 (with-test-prefix "decode"
   (pass-if "foo%20bar"