nillable fields are skipped by XmlSerializer

[barsv]

Hi,

I have nillable="true" in my xsd. I generated a python class for this xsd. I serialize the class into xml using XmlSerializer. My problem is that the nillable field is missing in the xml.
I have

            "required": True,
            "nillable": True,

in the generated code for the nillable field. So I think that XmlSerializer should generate an empty tag for this field.

I don't know if it's a bug or not. Could you please suggest.

More details:

I created a small repo to reproduce: https://github.com/barsv/xsdata-issue.git

My test.xsd file:

<?xml version="1.0" encoding="UTF-8" ?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">

<xs:element name="shiporder">
  <xs:complexType>
    <xs:sequence>
      <xs:element minOccurs="1" maxOccurs="1" name="name" nillable="true" type="xs:string"/>
    </xs:sequence>
  </xs:complexType>
</xs:element>

</xs:schema>

I generated test.py using xsdata test.xsd:

@dataclass
class Shiporder:
    class Meta:
        name = "shiporder"

    name: Optional[str] = field(
        default=None,
        metadata={
            "type": "Element",
            "namespace": "",
            "required": True,
            "nillable": True,
        }
    )

I serialize it using the following code:

config = SerializerConfig(pretty_print=True)
xml_serializer = XmlSerializer(config=config)

order = Shiporder()
#order.name = "test"
xml = xml_serializer.render(order)
print(xml)

and I get the following xml:

<?xml version="1.0" encoding="UTF-8"?>
<shiporder/>

This xml doesn't pass validation against the original xsd.

I would expect to get the following xml instead:

<?xml version="1.0" encoding="UTF-8"?>
<shiporder>
    <name/>
</shiporder>

ps: I'm not an expert in neither xsd nor python.

[tefra]

Initialize the field with an empty string.

order = Shiporder()
order.name = ""
xml = xml_serializer.render(order)
print(xml)

<?xml version="1.0" encoding="UTF-8"?>
<shiporder>
  <name xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:nil="true"/>
</shiporder

That's the parser's behavior as well

obj = XmlParser().from_string(xml, Shiporder)
print(obj)
# Shiporder(name='')

It seems a bit weird I agree and I can't really remember right now why I had to do it this way, I am going to take another look again.

[tefra]

I took out this behavior and run the w3c test suite, everything passed as expected, I still can't remember why I had to do that.

Thanks for reporting @barsv

[barsv]

Thank you! The empty string works good for me.

I want to add for others who might find this issue ticket in the future that the same workaround works for XmlDateTime as well.
I changed the type of the field from xs:string to xs:dateTime, regenerated the class, deserialized it using XmlParser from xml with empty tag and ... to my surprise I found that the field value in the deserialized object is empty string. And when I serialized the object back to xml it generated the empty tag and validates perfectly against the xsd.

I don't know if the issue should be closed though because the field type in the data class is name: Optional[XmlDateTime] =... while the value after deserialization is empty string. I would expect to have None instead of empty string.

[tefra]

No leave it open I am planning to change this behavior in the next release, to avoid the empty string hack I just need to test a few more things

[tefra]

Thank you for reporting @barsv the fix is on master and will be included in the next release.