[xml] detailed information in case of rng-validation-failure

["jean-gert nesselbosch" <nesselbosch strato-rz de>]

hello everybody,

I'm using "xmlRelaxNGSetValidStructuredErrors" to trigger my own
error-handling-function. in this function I'm trying to get as much information
as there is about the validation-error that occured by reading the entries
of the "xmlError"-struct that's passed through to my handler.

what I'm missing is some detailed information about the actual rng-pattern
or rng-section that caused the validation-error.

a dull example may help to clarify what my aim is :

### here's my (non-valid) xml-instance :

<?xml version="1.0"?>
<fitze>
 <fatze>schnullifutz</fatze>
</fitze>

### this is my rng :

<?xml version="1.0"?>
<grammar xmlns="http://relaxng.org/ns/structure/1.0"; 
datatypeLibrary="http://www.w3.org/2001/XMLSchema-datatypes";>
<start>
<element name="fitze">
 <element name="fatze">
    <data type="string">
        <param name="pattern">schnulli|schnalli</param>
    </data>
 </element>   
</element>
</start>
</grammar>

### this is part of the "xmlError"-struct :

error_line is : 3
domain is : 19
code is : 31
message is : Error validating datatype string

file is : /home/jean/xs/test.xml
str1 is : string
str2 is : (null)
str3 is : (null)
int1 is : 0
column-number is : 0

error_line is : 3
domain is : 19
code is : 25
message is : Element fatze failed to validate content

file is : /home/jean/xs/test.xml
str1 is : fatze
str2 is : (null)
str3 is : (null)
int1 is : 0
column-number is : 0
instance fails to validate 

...("node" and "ctxt" from  "xmlError" I did not dump)

###

it's clear, why this instance is not valid,
but, at least as far as I can see, there's no
information about the rng-pattern that
prevented my instance from being valid
to be found in the xmlError-struct.
(of course, in this case it's ' <param name="pattern">schnulli|schnalli</param>')

would be nice, if there would be something like this in xmlError :

message : "Element fatze failed to match regex"
line : 7
regex : schnulli|schnalli

at least *some* reference to the part of the rng-schema
that kept the instance from beeing valid. 

sorry for the lengthy text.

thanks in advance,
jean-gert