Merge pull request #63 from surenkov/58-error-constructing-model-inst…

…ance-with-no-field-default

Bypass field validation on model instantiation if it does not contain a `default=` argument

Makefile

@@ -1,34 +1,45 @@
- DJANGO_SETTINGS_MODULE ?= "tests.settings.django_test_settings"
-
-.PHONY: install build test lint upload upload-test clean
+export DJANGO_SETTINGS_MODULE=tests.settings.django_test_settings
 
+.PHONY: install
 install:
 	python3 -m pip install build twine
 	python3 -m pip install -e .[dev,test]
 
+.PHONY: build
 build:
 	python3 -m build
 
+.PHONY: migrations
 migrations:
 	python3 -m django makemigrations --noinput
 
+.PHONY: runserver
 runserver:
 	python3 -m django migrate && \
 	python3 -m django runserver
 
+.PHONY: check
+check:
+	python3 -m django check
+
+.PHONY: test
 test: A=
 test:
 	pytest $(A)
 
+.PHONY: lint
 lint: A=.
 lint:
 	python3 -m mypy $(A)
 
+.PHONY: upload
 upload:
 	python3 -m twine upload dist/*
 
+.PHONY: upload-test
 upload-test:
 	python3 -m twine upload --repository testpypi dist/*
 
+.PHONY: clean
 clean:
 	rm -rf dist/*

django_pydantic_field/v1/fields.py

@@ -37,8 +37,14 @@ def __set__(self, obj, value):
         obj.__dict__[self.field.attname] = self.field.to_python(value)
 
 
+class UninitializedSchemaAttribute(SchemaAttribute):
+    def __set__(self, obj, value):
+        if value is not None:
+            value = self.field.to_python(value)
+        obj.__dict__[self.field.attname] = value
+
+
 class PydanticSchemaField(JSONField, t.Generic[base.ST]):
-    descriptor_class = SchemaAttribute
     _is_prepared_schema: bool = False
 
     def __init__(
@@ -61,8 +67,10 @@ def __copy__(self):
         return copied
 
     def get_default(self):
-        value = super().get_default()
-        return self.to_python(value)
+        default_value = super().get_default()
+        if self.has_default():
+            return self.to_python(default_value)
+        return default_value
 
     def to_python(self, value) -> "base.SchemaT":
         # Attempt to resolve forward referencing schema if it was not succesful
@@ -104,6 +112,12 @@ def deconstruct(self):
 
         return name, path, args, kwargs
 
+    @staticmethod
+    def descriptor_class(field: "PydanticSchemaField") -> DeferredAttribute:
+        if field.has_default():
+            return SchemaAttribute(field)
+        return UninitializedSchemaAttribute(field)
+
     def contribute_to_class(self, cls, name, private_only=False):
         if self.schema is None:
             self._resolve_schema_from_type_hints(cls, name)
@@ -162,8 +176,7 @@ def _prepare_model_schema(self, cls=None):
 
     def _deconstruct_default(self, kwargs):
         default = kwargs.get("default", NOT_PROVIDED)
-
-        if not (default is NOT_PROVIDED or callable(default)):
+        if default is not NOT_PROVIDED and not callable(default):
             if self._is_prepared_schema:
                 default = self.get_prep_value(default)
             kwargs.update(default=default)
@@ -202,6 +215,6 @@ def SchemaField(
 ) -> "base.ST": ...
 
 
-def SchemaField(schema=None, config=None, default=None, *args, **kwargs) -> t.Any:
+def SchemaField(schema=None, config=None, default=NOT_PROVIDED, *args, **kwargs) -> t.Any:  # type: ignore
     kwargs.update(schema=schema, config=config, default=default)
     return PydanticSchemaField(*args, **kwargs)

django_pydantic_field/v2/fields.py

@@ -63,8 +63,14 @@ def __set__(self, obj, value):
         obj.__dict__[self.field.attname] = self.field.to_python(value)
 
 
+class UninitializedSchemaAttribute(SchemaAttribute):
+    def __set__(self, obj, value):
+        if value is not None:
+            value = self.field.to_python(value)
+        obj.__dict__[self.field.attname] = value
+
+
 class PydanticSchemaField(JSONField, ty.Generic[types.ST]):
-    descriptor_class: type[DeferredAttribute] = SchemaAttribute
     adapter: types.SchemaAdapter
 
     def __init__(
@@ -102,6 +108,12 @@ def deconstruct(self) -> ty.Any:
 
         return field_name, import_path, args, kwargs
 
+    @staticmethod
+    def descriptor_class(field: PydanticSchemaField) -> DeferredAttribute:
+        if field.has_default():
+            return SchemaAttribute(field)
+        return UninitializedSchemaAttribute(field)
+
     def contribute_to_class(self, cls: types.DjangoModelType, name: str, private_only: bool = False) -> None:
         self.adapter.bind(cls, name)
         super().contribute_to_class(cls, name, private_only)
@@ -118,7 +130,8 @@ def check(self, **kwargs: ty.Any) -> list[checks.CheckMessage]:
 
         try:
             # Test that the default value conforms to the schema.
-            self.get_prep_value(self.get_default())
+            if self.has_default():
+                self.get_prep_value(self.get_default())
         except pydantic.ValidationError as exc:
             message = f"Default value cannot be adapted to the schema. Pydantic error: \n{str(exc)}"
             performed_checks.append(checks.Error(message, obj=self, id="pydantic.E002"))

tests/test_fields.py

@@ -314,3 +314,10 @@ def test_copy_field():
     assert copied.name == Building.meta.field.name
     assert copied.attname == Building.meta.field.attname
     assert copied.concrete == Building.meta.field.concrete
+
+
+def test_model_init_no_default():
+    try:
+        SampleModel()
+    except Exception:
+        pytest.fail("Model with schema field without a default value should be able to initialize")