Please describe the problem:
Inserting XML Schema default attributes does not work when parsing with the SAX-plug (i.e. when validating at parse time). It would be really nice if this worked, as applying the validation afterwards to insert the 'missing' attributes requires an additional step, so the parser itself cannot currently return the 'complete' document as seen by the external schema.

Steps to reproduce:
1. create a validation context and set the XML_SCHEMA_VAL_VC_I_CREATE option
2. insert the validator into a parser using xmlSchemaSAXPlug()
3. validate a document against a schema that contains default attributes

The schema document I use is

'''
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema">
  <xsd:element name="a" type="AType"/>
  <xsd:complexType name="AType">
    <xsd:sequence minOccurs="4" maxOccurs="4">
      <xsd:element name="b" type="BType" />
    </xsd:sequence>
  </xsd:complexType>
  <xsd:complexType name="BType">
    <xsd:attribute name="hardy" type="xsd:string" default="hey" />
  </xsd:complexType>
</xsd:schema>
'''

The document I parse is

'''
<a><b hardy="ho"/><b/><b hardy="ho"/><b/></a>
'''


Actual results:
The default attributes defined in the schema do not end up in the document tree.

Expected results:


Does this happen every time?


Other information:
I debugged into this a bit and found line 25351 in xmlschemas.c (libxml2 2.7.3), where it says:

'''
    /*
    * Get the owner element; needed for creation of default attributes.
    * This fixes bug #341337, reported by David Grohmann.
    */
    if (vctxt->options & XML_SCHEMA_VAL_VC_I_CREATE) {
        xmlSchemaNodeInfoPtr ielem = vctxt->elemInfos[vctxt->depth];
==>     if (ielem && ielem->node && ielem->node->doc)
            defAttrOwnerElem = ielem->node;
    }
'''

"ielem->node" is NULL every time it gets there, so the attributes do not get inserted.