feat: add XML serialization support for Pydantic models

src/pydantify_common/__init__.py

@@ -1,3 +1,4 @@
-from .model import PydantifyModel
+from .model import PydantifyModel, XMLPydantifyModel
+from .helper import model_dump_xml_string, NETCONF_BASE_NS
 
-__all__ = ["PydantifyModel"]
+__all__ = ["PydantifyModel", "XMLPydantifyModel", "model_dump_xml_string", "NETCONF_BASE_NS"]

src/pydantify_common/helper.py

@@ -1,14 +1,31 @@
 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(
     model: XMLPydantifyModel, *, pretty_print: bool = False, data_root: bool = False
 ) -> str:
-    data = model.model_dump_xml()
+    """
+    Serialize model to XML string.
+
+    Args:
+        model: The XMLPydantifyModel to serialize
+        pretty_print: If True, format with indentation
+        data_root: If True, wrap in <data xmlns="...netconf..."> root
+
+    Returns:
+        XML string representation
+    """
+    xml_element = model.model_dump_xml()
+
     if data_root:
         # Add `<data xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">` root element
-        pass
+        data_elem = etree.Element(
+            f"{{{NETCONF_BASE_NS}}}data", nsmap={None: NETCONF_BASE_NS}
+        )
+        data_elem.append(xml_element)
+        xml_element = data_elem
 
-    return etree.tostring(data, encoding=str, pretty_print=pretty_print)
+    return etree.tostring(xml_element, encoding=str, pretty_print=pretty_print)

src/pydantify_common/model.py

@@ -12,5 +12,152 @@ class XMLPydantifyModel(PydantifyModel):
     namespace: ClassVar[str]
     prefix: ClassVar[str]
 
-    def model_dump_xml(self) -> etree.Element:
-        pass
+    def model_dump_xml(self, parent_namespace: str | None = None) -> etree._Element:
+        """
+        Serialize model to lxml Element with namespace support.
+
+        Args:
+            parent_namespace: The namespace of the parent element. Used to determine
+                             whether to declare xmlns attribute on this element.
+
+        Returns:
+            lxml Element representing this model.
+        """
+        # Check if this is a wrapper model (single XMLPydantifyModel field)
+        # If so, delegate to that child model
+        wrapper_child = self._get_wrapper_child()
+        if wrapper_child is not None:
+            return wrapper_child.model_dump_xml(parent_namespace=parent_namespace)
+
+        # 1. Get local name from first field's alias
+        local_name = self._get_xml_local_name()
+
+        # 2. Build qualified tag using Clark notation
+        tag = f"{{{self.namespace}}}{local_name}"
+
+        # 3. Only add nsmap if namespace differs from parent
+        nsmap = None
+        if self.namespace != parent_namespace:
+            nsmap = {None: self.namespace}  # Default namespace declaration
+
+        # 4. Create element
+        element = etree.Element(tag, nsmap=nsmap)
+
+        # 5. Iterate through model fields and add children
+        self._serialize_fields_to_element(element)
+
+        return element
+
+    def _get_wrapper_child(self) -> "XMLPydantifyModel | None":
+        """
+        Check if this model is a "wrapper" with a single XMLPydantifyModel field.
+
+        Returns:
+            The child XMLPydantifyModel if this is a wrapper, otherwise None.
+        """
+        fields = self.__class__.model_fields
+        if len(fields) != 1:
+            return None
+
+        field_name = next(iter(fields.keys()))
+        value = getattr(self, field_name)
+
+        if isinstance(value, XMLPydantifyModel):
+            return value
+
+        return None
+
+    def _serialize_fields_to_element(self, element: etree._Element) -> None:
+        """
+        Serialize all model fields as child elements.
+
+        Args:
+            element: The parent element to add children to.
+        """
+        for field_name, field_info in self.__class__.model_fields.items():
+            value = getattr(self, field_name)
+            if value is None:
+                continue
+
+            # Get local name from alias (e.g., "config:name" → "name")
+            alias = field_info.alias or field_name
+            child_local_name = alias.split(":")[-1] if ":" in alias else alias
+
+            if isinstance(value, XMLPydantifyModel):
+                # Nested model - create element from field alias and namespace from child
+                child_elem = self._create_child_model_element(
+                    child_local_name, value, self.namespace
+                )
+                element.append(child_elem)
+            elif isinstance(value, list):
+                for item in value:
+                    if isinstance(item, XMLPydantifyModel):
+                        child_elem = self._create_child_model_element(
+                            child_local_name, item, self.namespace
+                        )
+                        element.append(child_elem)
+                    else:
+                        # Primitive list item
+                        child_tag = f"{{{self.namespace}}}{child_local_name}"
+                        child_elem = etree.SubElement(element, child_tag)
+                        child_elem.text = str(item)
+            else:
+                # Primitive value
+                child_tag = f"{{{self.namespace}}}{child_local_name}"
+                child_elem = etree.SubElement(element, child_tag)
+                child_elem.text = str(value)
+
+    def _create_child_model_element(
+        self,
+        local_name: str,
+        child_model: "XMLPydantifyModel",
+        parent_namespace: str
+    ) -> etree._Element:
+        """
+        Create an element for a child XMLPydantifyModel using the parent's field alias
+        for the element name.
+
+        Args:
+            local_name: The local name for the element (from parent's field alias).
+            child_model: The child XMLPydantifyModel to serialize.
+            parent_namespace: The namespace of the parent element.
+
+        Returns:
+            lxml Element with the child's content.
+        """
+        # Use child's namespace for the tag
+        tag = f"{{{child_model.namespace}}}{local_name}"
+
+        # Only add nsmap if child's namespace differs from parent's
+        nsmap = None
+        if child_model.namespace != parent_namespace:
+            nsmap = {None: child_model.namespace}
+
+        # Create element
+        element = etree.Element(tag, nsmap=nsmap)
+
+        # Let the child model fill in its children
+        child_model._serialize_fields_to_element(element)
+
+        return element
+
+    def _get_xml_local_name(self) -> str:
+        """
+        Extract the local name for this model's XML element.
+
+        Uses the first field's alias to extract the local name.
+        Falls back to the lowercase class name if no fields exist.
+        """
+        # Try to get local name from first field's alias
+        if self.__class__.model_fields:
+            first_field_info = next(iter(self.__class__.model_fields.values()))
+            alias = first_field_info.alias
+            if alias:
+                # Extract prefix from "prefix:localname" pattern
+                # e.g., "configuration:devicename" → "configuration"
+                parts = alias.split(":")
+                if len(parts) >= 1:
+                    return parts[0]
+
+        # Fallback to lowercase class name
+        return self.__class__.__name__.lower()

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