spyne generating invalid schema - lxml

Question

I am trying to use spyne from master branch as the released versions are not compatible with python3 and I have models defined like these:
class currency(ComplexModel):
data = XmlData(Decimal)
class mntCurrency(currency):
code = XmlAttribute(String)
class CreditLmt(ComplexModel):
curr = mntCurrency
I have plugged these models into a simple HelloWorld Service which returns CreditLmt in response. But when I try to run my soap server, spyne complains with the following:
lxml.etree.XMLSchemaParseError: Element
'{http://www.w3.org/2001/XMLSchema}extension': The content is not
valid. Expected is (annotation?, ((group | all | choice | sequence)?,
((attribute | attributeGroup)*, anyAttribute?)))., line 16
Which is correct because spyne generates the following xsd:
<xs:complexType name="mntCurrency">
<xs:complexContent>
<xs:extension base="tns:currency">
<xs:simpleContent>
<xs:extension base="xs:decimal">
<xs:attribute name="code" type="xs:string"/>
</xs:extension>
</xs:simpleContent>
<xs:sequence>
<xs:element name="test" type="xs:token" minOccurs="0" nillable="true"/>
</xs:sequence>
</xs:extension>
</xs:complexContent>
</xs:complexType>
I am using XmlData because I want to have reponse such that it looks like this:
<tns:currency code="826">10.0</tns:currency>
So how do I define my models?

Answer 1

An example for generating this element:
<tns:currency code="826">10.0</tns:currency>
... is as follows:
from spyne import *
from spyne.util.xml import get_object_as_xml
from lxml import etree
class Currency(ComplexModel):
value = XmlData(Decimal)
code = XmlAttribute(Integer32(values=[826, 234, 555]))
class SomeObject(ComplexModel):
handle = Unicode
currency = Currency
obj = SomeObject(handle="aaaa", currency=Currency(value=D('123.45'), code=555))
elt = get_object_as_xml(obj)
print(etree.tostring(elt, pretty_print=True))
As for the error, it is coming directly from libxml. It is essentially saying that the Xml Schema standard doesn't allow lone XmlData entries in a ComplexModel subclass. If you think this is an error, you must complain to the Xml Schema working group.