Do not duplicate nofollow attribute in transform.

Signed-off-by: Edward Z. Yang <ezyang@mit.edu>

NEWS

@@ -15,6 +15,8 @@ NEWS ( CHANGELOG and HISTORY )                                     HTMLPurifier
 - Color keywords are now case insensitive.  Thanks Yzmir Ramirez
   <yramirez-htmlpurifier@adicio.com> for reporting.
 - Explicitly initialize anonModule variable to null.
+- Do not duplicate nofollow if already present.  Thanks 178
+  for reporting.
 
 4.3.0, released 2011-03-27
 # Fixed broken caching of customized raw definitions, but requires an

library/HTMLPurifier/AttrTransform/Nofollow.php

@@ -26,7 +26,11 @@ class HTMLPurifier_AttrTransform_Nofollow extends HTMLPurifier_AttrTransform
 
         if (!is_null($url->host) && $scheme !== false && $scheme->browsable) {
             if (isset($attr['rel'])) {
-                $attr['rel'] .= ' nofollow';
+                $rels = explode(' ', $attr);
+                if (!in_array('nofollow', $rels)) {
+                    $rels[] = 'nofollow';
+                }
+                $attr['rel'] = implode(' ', $rels);
             } else {
                 $attr['rel'] = 'nofollow';
             }

tests/HTMLPurifier/HTMLModule/NofollowTest.php

@@ -15,6 +15,12 @@ class HTMLPurifier_HTMLModule_NofollowTest extends HTMLPurifier_HTMLModuleHarnes
         );
     }
 
+    function testNofollowDupe() {
+        $this->assertResult(
+            '<a href="http://google.com" rel="nofollow">a</a><a href="/local">b</a><a href="mailto:foo@example.com">c</a>'
+        );
+    }
+
 }
 
 // vim: et sw=4 sts=4