[xml] XPath queries on document fragments without a document

[Christian Glahn <christian glahn uibk ac at>]

hi all,

while tracing a problem with XPath queries and document fragments I found
that it is not possible to  XPath query an document fragment, that is 
parsed by xmlParseBalancedChunkMemory(). this means the fragment does not
belong to a document tree ( node->doc == NULL ).

now a xpath query run through xmlXPathCompiledEval() on such a fragment will 
allways returns nothing. apart from i think it's anoying ;) i wonder if there 
is a reason to refuse such queries. 

i found removing the following lines in xpath.c made such queries possible.
queries from on the document root just returned -- correctly -- no value.

----8<-----8<------8<-------8<-------8<-------8<------
3673,3682d3672
     else if (ctxt->doc == NULL) {                                     \
         xmlGenericError(xmlGenericErrorContext,                              \
               "%s:%d Internal error: no document\n",                  \
               __FILE__, __LINE__);                                    \
     }                                                                 \
     else if (ctxt->doc->children == NULL) {                           \
         xmlGenericError(xmlGenericErrorContext,                              \
               "%s:%d Internal error: document without root\n",        \
               __FILE__, __LINE__);                                    \
     }                                                                 \

----8<-----8<------8<-------8<-------8<-------8<------

my question is now: is there a reason to refuse xpath queries on 
document fragments?

thanks 
christian