AnydataNode.to_xml() fails

[kwatsen]

@HRogge

The test_xml_config pytest in test-models.py in my xml-improved fork currently comments-out anydA. But if its removal is commented-out in the xml_safe_data() as follows:

OLD:

data2['test:contA'].pop('anydA')

NEW:

#data2['test:contA'].pop('anydA')

And run:

pytest -sxvv -k test_xml_config

Then the following output is produced:

  <snip/>
        # convert InstanceValue to an XML-encoded string
>       xml_obj = inst.to_xml()

tests/test_model.py:741: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
yangson/instance.py:708: in to_xml
    et = super().to_xml(filter, element)
yangson/instance.py:540: in to_xml
    m.to_xml(filter, child)
yangson/instance.py:540: in to_xml
    m.to_xml(filter, child)
yangson/instance.py:507: in to_xml
    m = self[cname]
yangson/instance.py:219: in __getitem__
    return self._member(key)
yangson/instance.py:580: in _member
    self._member_schema_node(name), self.value.timestamp)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

self = <yangson.instance.ObjectMember object at 0x10777d4f0>, name = 'foo:bar'

    def _member_schema_node(self: InstanceNode, name: InstanceName) -> DataNode:
        qname = self.schema_node._iname2qname(name)
>       res = self.schema_node.get_data_child(*qname)
E       AttributeError: 'AnydataNode' object has no attribute 'get_data_child'

yangson/instance.py:609: AttributeError
=============================================== short test summary info ===============================================
FAILED tests/test_model.py::test_xml_config - AttributeError: 'AnydataNode' object has no attribute 'get_data_child'
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! stopping after 1 failures !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
========================================== 1 failed, 15 deselected in 0.67s ===========================================

[kwatsen]

Since the anydata and anyxml statements are opaque, by definition, how would it be possible to serialize XML?

Maybe the code could blindly walk the data tree, converting namespace prefixes to xmlns entries. Since JSON lists are self-describing, the conversion seems possible.

Of course, this assumes that all the prefixes are recognized, which may not be true. A user-configurable "prefix to xml-namespace" table could be used to assist.

Thoughts?

[llhotka]

I don't think any general conversion method can work for everybody. For special use cases, I'd suggest to (fork and) extend Yangson in an ad hoc fashion.