[xml] Fix for bug 105992 incorrect? (and a patch)

[Brent Hendricks <brentmh ece rice edu>]

I started seeing http://bugzilla.gnome.org/show_bug.cgi?id=105992 again, 
but this time on namespace declarations that were *not* the same as 
current element.  For example, in the following XML file, the xmlns:a 
attribute passed through OK but xmlns:b was declared invalid:

<?xml version="1.0"?>
<!DOCTYPE a:outer [

<!ELEMENT a:outer EMPTY>
<!ATTLIST a:outer xmlns:a CDATA #FIXED 'urn:namespace'>
<!ATTLIST a:outer xmlns:b CDATA #FIXED 'urn:namespaceb'>
]>

<a:outer />


Thinking that this was simply bug 105992 popping up in a different 
place, I looked at the fix to see if there was a case that was missed. 
After some digging, I believe that the current fix is incorrect.  I'll 
present 3 different situations: the code pre 2.5.4, the code as it 
stands now, and my proposed fix.

pre-2.5.4:

When validating namespace attributes, my_attribute() calls 
xmlValidateOneNamespace() passing the newly created xmlNsPtr, and the 
prefix of the *current element* that it received as an argument. 
xmlValidateOneNamespace() uses this prefix to create a qname for looking 
up attributes in the DTD.  However, xmlCheckDefaultedAttributes() calls 
attribute(), which passes NULL to my_attribute() as the prefix.  Hence, 
all #FIXED namespace attributes are declared invalid on qualified 
elments.  In the above example it looks up 'xmlns:a' and 'xmlns:b' for 
element 'outer' and doesn't find either in the DTD because the element 
is 'a:outer', not 'outer'

current libxml2:

The fix for 105992 substituted the namespace declaration's prefix (eg. 
the 'a' in 'xmlns:a') for the element prefix in the call to 
xmlValidateOneNamespace().  This worked for the testcase submitted with 
the bug since the element prefix and namespace prefix were the same. 
However, it fails in the above testcase where you declare a namespace 
with a different prefix. xmlValidateOneNamespace() looks for 'xmlns:a' 
in 'a:outer' and finds it.    But then it looks for 'xmlns:b' in 
'b:outer' and doesn't find it because 'b:outer' doesn't exist.

My proposed fix (attached):

This patch reverts the previous fix, since we really do want to pass the 
element prefix, not the namespace declaration prefix.  It also modifies 
xmlCheckDefaultedAttributes() to call my_attribute() with the element 
prefix.  Now the prefix has the correct value ('a') in 
xmlValidateOneNamespace() and is able to find both namespace attributes 
in the DTD.


Thanks,
Brent

-------------------------------------------------------------------------

"The programmer, like the poet, works only slightly removed from pure
 thought-stuff.  He builds his castles in the air, from air, creating
 by exertion of the imagination.  Few media of creation are so
 flexible, so easy to polish and rework, so readily capable of
 realizing grand conceptual structures."
                        -- Frederick Brooks, Jr., The Mythical Man Month

--- SAX.c.orig  Sun Mar 23 04:20:44 2003
+++ SAX.c       Wed Mar 26 09:49:33 2003
@@ -968,7 +968,7 @@
         if (nsret != NULL && ctxt->validate && ctxt->wellFormed &&
            ctxt->myDoc && ctxt->myDoc->intSubset)
            ctxt->valid &= xmlValidateOneNamespace(&ctxt->vctxt, ctxt->myDoc,
-                                          ctxt->node, name, nsret, value);
+                                          ctxt->node, prefix, nsret, value);
        if (name != NULL) 
            xmlFree(name);
        if (nval != NULL)
@@ -1236,7 +1236,7 @@
                            }
                        }
                        if (att == NULL) {
-                           attribute(ctxt, fulln, attr->defaultValue);
+                           my_attribute(ctxt, fulln, attr->defaultValue, prefix);
                        }
                        xmlFree(fulln);
                    }