Fix XML namespace serialization to only add xmlns when needed

src/pydantify_common/helper.py

@@ -1,6 +1,7 @@
 from lxml import etree
 from .model import XMLPydantifyModel
-from typing import Any
+
+NETCONF_BASE_NS = "urn:ietf:params:xml:ns:netconf:base:1.0"
 
 
 def model_dump_xml_string(
@@ -9,6 +10,8 @@ def model_dump_xml_string(
     data = model.model_dump_xml()
     if data_root:
         # Add `<data xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">` root element
-        pass
+        root = etree.Element("data", nsmap={None: NETCONF_BASE_NS})
+        root.append(data)
+        data = root
 
     return etree.tostring(data, encoding=str, pretty_print=pretty_print)

src/pydantify_common/model.py

@@ -12,5 +12,92 @@ class XMLPydantifyModel(PydantifyModel):
     namespace: ClassVar[str]
     prefix: ClassVar[str]
 
-    def model_dump_xml(self) -> etree.Element:
-        pass
+    def fields_to_elements(
+        self,
+        container_name: str | None = None,
+        parent_namespace: str | None = None,
+    ) -> list[etree._Element]:
+        """Convert model fields to XML elements.
+
+        Args:
+            container_name: If provided, wrap elements in a container with this name
+            parent_namespace: The namespace of the parent element, used to determine
+                             if xmlns declaration is needed
+        """
+        elements: list[etree._Element] = []
+
+        # Get field info from model class (not instance to avoid deprecation warning)
+        for field_name, field_info in self.__class__.model_fields.items():
+            value = getattr(self, field_name)
+            if value is None:
+                continue
+
+            # Get the XML element name from alias or field name
+            xml_name = field_info.alias if field_info.alias else field_name
+            # Strip prefix (e.g., "configuration:devicename" -> "devicename")
+            if ":" in xml_name:
+                xml_name = xml_name.split(":", 1)[1]
+
+            # Handle XMLPydantifyModel instances (nested models)
+            if isinstance(value, XMLPydantifyModel):
+                child_elements = value.fields_to_elements(
+                    container_name=xml_name,
+                    parent_namespace=self.namespace,
+                )
+                elements.extend(child_elements)
+            # Handle lists
+            elif isinstance(value, list):
+                for item in value:
+                    if isinstance(item, XMLPydantifyModel):
+                        child_elements = item.fields_to_elements(
+                            container_name=xml_name,
+                            parent_namespace=self.namespace,
+                        )
+                        elements.extend(child_elements)
+                    else:
+                        # Primitive list item
+                        elem = etree.Element(xml_name)
+                        elem.text = str(item)
+                        elements.append(elem)
+            else:
+                # Primitive field
+                elem = etree.Element(xml_name)
+                elem.text = str(value)
+                elements.append(elem)
+
+        # Wrap in container if container_name is provided
+        if container_name:
+            # Only add xmlns when namespace differs from parent
+            if parent_namespace is None or self.namespace != parent_namespace:
+                root = etree.Element(container_name, nsmap={None: self.namespace})
+            else:
+                root = etree.Element(container_name)
+            for elem in elements:
+                root.append(elem)
+            return [root]
+
+        return elements
+
+    def model_dump_xml(self) -> etree._Element:
+        """Convert model to XML element tree."""
+        # Get the first field and use it as the root element
+        for field_name, field_info in self.__class__.model_fields.items():
+            value = getattr(self, field_name)
+            if value is None:
+                continue
+
+            xml_name = field_info.alias if field_info.alias else field_name
+            if ":" in xml_name:
+                xml_name = xml_name.split(":", 1)[1]
+
+            if isinstance(value, XMLPydantifyModel):
+                elements = value.fields_to_elements(
+                    container_name=xml_name,
+                    parent_namespace=None,
+                )
+                if elements:
+                    return elements[0]
+
+        # Fallback: return self as root
+        elements = self.fields_to_elements(container_name=self.prefix)
+        return elements[0] if elements else etree.Element(self.prefix)

tests/examples/with_augment/model.py

@@ -2,7 +2,7 @@
 
 from typing import Annotated, List, ClassVar
 
-from pydantic import ConfigDict, Field, RootModel
+from pydantic import ConfigDict, Field
 from pydantify_common.model import XMLPydantifyModel
 
 

tests/examples/with_import_uses/model.py

@@ -2,7 +2,7 @@
 
 from typing import Annotated, List, ClassVar
 
-from pydantic import ConfigDict, Field, RootModel
+from pydantic import ConfigDict, Field
 from pydantify_common.model import XMLPydantifyModel
 
 

tests/test_examples.py

@@ -1,5 +1,4 @@
 from pathlib import Path
-from pydantify_common.model import XMLPydantifyModel
 from pydantify_common.helper import model_dump_xml_string
 from lxml import etree