Merge pull request #261 from dapper91/feat/annotated-field-validator-serializer

feat: annotated form of field serializer/validator support added.

Author: dapper91

docs/source/pages/misc.rst

@@ -54,15 +54,23 @@ The following example illustrate how to serialize ``xs:list`` element:
 
 *model.py:*
 
-.. literalinclude:: ../../../examples/xml-serialization/model.py
+.. literalinclude:: ../../../examples/xml-serialization-decorator/model.py
     :language: python
 
 *doc.xml:*
 
-.. literalinclude:: ../../../examples/xml-serialization/doc.xml
+.. literalinclude:: ../../../examples/xml-serialization-decorator/doc.xml
     :language: xml
 
 
+``pydantic-xml`` also supports the ``Annotated`` typing form to attach metadata to an annotation:
+
+*model.py:*
+
+.. literalinclude:: ../../../examples/xml-serialization-annotation/model.py
+    :language: python
+
+
 Optional type encoding
 ~~~~~~~~~~~~~~~~~~~~~~
 

examples/xml-serialization/doc.xml renamed to examples/xml-serialization-annotation/doc.xml

@@ -0,0 +1,47 @@
+import pathlib
+from typing import Annotated, List, Type
+from xml.etree.ElementTree import canonicalize
+
+import pydantic_xml as pxml
+from pydantic_xml.element import XmlElementReader, XmlElementWriter
+
+
+def validate_space_separated_list(
+        cls: Type[pxml.BaseXmlModel],
+        element: XmlElementReader,
+        field_name: str,
+) -> List[float]:
+    if element := element.pop_element(field_name, search_mode=cls.__xml_search_mode__):
+        return list(map(float, element.pop_text().split()))
+
+    return []
+
+
+def serialize_space_separated_list(
+        model: pxml.BaseXmlModel,
+        element: XmlElementWriter,
+        value: List[float],
+        field_name: str,
+) -> None:
+    sub_element = element.make_element(tag=field_name, nsmap=None)
+    sub_element.set_text(' '.join(map(str, value)))
+
+    element.append_element(sub_element)
+
+
+SpaceSeparatedValueList = Annotated[
+    List[float],
+    pxml.XmlFieldValidator(validate_space_separated_list),
+    pxml.XmlFieldSerializer(serialize_space_separated_list),
+]
+
+
+class Plot(pxml.BaseXmlModel):
+    x: SpaceSeparatedValueList = pxml.element()
+    y: SpaceSeparatedValueList = pxml.element()
+
+
+xml_doc = pathlib.Path('./doc.xml').read_text()
+plot = Plot.from_xml(xml_doc)
+
+assert canonicalize(plot.to_xml(), strip_text=True) == canonicalize(xml_doc, strip_text=True)

examples/xml-serialization-annotation/model.py

@@ -0,0 +1,4 @@
+<Plot>
+    <x>0.0 1.0 2.0 3.0 4.0 5.0</x>
+    <y>0.0 3.2 5.4 4.1 2.0 -1.2</y>
+</Plot>

examples/xml-serialization-decorator/doc.xml

@@ -4,8 +4,8 @@
 
 from . import config, errors, model
 from .errors import ModelError, ParsingError
-from .model import BaseXmlModel, RootXmlModel, attr, computed_attr, computed_element, create_model, element, wrapped
-from .model import xml_field_serializer, xml_field_validator
+from .model import BaseXmlModel, RootXmlModel, XmlFieldSerializer, XmlFieldValidator, attr, computed_attr
+from .model import computed_element, create_model, element, wrapped, xml_field_serializer, xml_field_validator
 
 __all__ = (
     'BaseXmlModel',
@@ -22,4 +22,6 @@
     'model',
     'xml_field_serializer',
     'xml_field_validator',
+    'XmlFieldValidator',
+    'XmlFieldSerializer',
 )

examples/xml-serialization/model.py renamed to examples/xml-serialization-decorator/model.py

@@ -26,6 +26,8 @@
     'computed_element',
     'xml_field_serializer',
     'xml_field_validator',
+    'XmlFieldSerializer',
+    'XmlFieldValidator',
     'BaseXmlModel',
     'RootXmlModel',
 )
@@ -355,6 +357,16 @@ def wrapper(func: SerializerFuncT) -> SerializerFuncT:
     return wrapper
 
 
+@dc.dataclass(frozen=True)
+class XmlFieldValidator:
+    func: ValidatorFunc
+
+
+@dc.dataclass(frozen=True)
+class XmlFieldSerializer:
+    func: SerializerFunc
+
+
 @te.dataclass_transform(kw_only_default=True, field_specifiers=(attr, element, wrapped, pd.Field))
 class XmlModelMeta(ModelMetaclass):
     """
@@ -374,8 +386,32 @@ def __new__(
         if not is_abstract:
             cls.__build_serializer__()
 
+        cls._collect_xml_field_serializers_validators(cls)
+
         return cls
 
+    @classmethod
+    def _collect_xml_field_serializers_validators(mcls, cls: Type['BaseXmlModel']) -> None:
+        for field_name, field_info in cls.model_fields.items():
+            for metadatum in field_info.metadata:
+                if isinstance(metadatum, XmlFieldValidator):
+                    cls.__xml_field_validators__[field_name] = metadatum.func
+                if isinstance(metadatum, XmlFieldSerializer):
+                    cls.__xml_field_serializers__[field_name] = metadatum.func
+
+        # find custom validators/serializers in all defined attributes
+        # though we want to skip any BaseModel attributes, as these can never be field
+        # serializers/validators, and getting certain pydantic fields
+        # may cause recursion errors for recursive / self-referential models
+        for attr_name in set(dir(cls)) - set(dir(BaseModel)):
+            if func := getattr(cls, attr_name, None):
+                if fields := getattr(func, '__xml_field_serializer__', None):
+                    for field in fields:
+                        cls.__xml_field_serializers__[field] = func
+                if fields := getattr(func, '__xml_field_validator__', None):
+                    for field in fields:
+                        cls.__xml_field_validators__[field] = func
+
 
 ModelT = TypeVar('ModelT', bound='BaseXmlModel')
 
@@ -435,19 +471,6 @@ def __init_subclass__(
         cls.__xml_field_serializers__ = {}
         cls.__xml_field_validators__ = {}
 
-        # find custom validators/serializers in all defined attributes
-        # though we want to skip any Base(Xml)Model attributes, as these can never be field
-        # serializers/validators, and getting certain pydantic fields, like __pydantic_post_init__
-        # may cause recursion errors for recursive / self-referential models
-        for attr_name in set(dir(cls)) - set(dir(BaseXmlModel)):
-            if func := getattr(cls, attr_name, None):
-                if fields := getattr(func, '__xml_field_serializer__', None):
-                    for field in fields:
-                        cls.__xml_field_serializers__[field] = func
-                if fields := getattr(func, '__xml_field_validator__', None):
-                    for field in fields:
-                        cls.__xml_field_validators__[field] = func
-
     @classmethod
     def __build_serializer__(cls) -> None:
         if cls is BaseXmlModel:

pydantic_xml/__init__.py

@@ -37,7 +37,11 @@ def test_snippets_py39(snippet: Path):
         'generic-model',
         'quickstart',
         'self-ref-model',
-        'xml-serialization',
+        'xml-serialization-decorator',
+        pytest.param(
+            'xml-serialization-annotation',
+            marks=pytest.mark.skipif(sys.version_info < (3, 9), reason="requires python 3.9 and above"),
+        ),
     ],
 )
 def example_dir(request: pytest.FixtureRequest, monkeypatch: pytest.MonkeyPatch):