feat: support pydantic by_name

Author: adhtruong

docs/examples/configuration/test_example_12.py

@@ -0,0 +1,27 @@
+from pydantic import AliasPath, BaseModel, Field
+
+from polyfactory.factories.pydantic_factory import ModelFactory
+
+
+class User(BaseModel):
+    username: str = Field(..., validation_alias="user_name")
+    email: str = Field(..., validation_alias=AliasPath("contact", "email"))  # type: ignore[pydantic-alias]
+
+
+class UserFactory(ModelFactory[User]):
+    __by_name__ = True
+
+    # Set factory defaults using field names
+    username = "john_doe"
+
+
+def test_by_name() -> None:
+    # Factory uses model_validate with by_name=True
+    instance = UserFactory.build()
+    assert instance.username == "john_doe"
+    assert isinstance(instance.email, str)
+
+    # Can override factory defaults
+    instance2 = UserFactory.build(username="jane_doe", email="[email protected]")
+    assert instance2.username == "jane_doe"
+    assert instance2.email == "[email protected]"

docs/usage/configuration.rst

@@ -148,6 +148,24 @@ By default, ``__use_examples__`` is set to ``False.``
     :language: python
 
 
+Validation Aliases (Pydantic >= V2)
+------------------------------------
+
+If ``__by_name__`` is set to ``True``, then the factory will use ``model_validate()`` with the ``by_name`` parameter
+when creating model instances. This is useful when working with models that use validation aliases, such as
+``validation_alias`` or ``AliasPath``, as it allows the factory to handle these aliases automatically without
+requiring additional model configuration.
+
+By default, ``__by_name__`` is set to ``False.``
+
+.. literalinclude:: /examples/configuration/test_example_12.py
+    :caption: Validation Aliases with by_name
+    :language: python
+
+.. note::
+    This feature is only available for Pydantic V2 models. For Pydantic V1 models, this setting has no effect.
+
+
 Forward References
 ------------------
 

polyfactory/factories/pydantic_factory.py

@@ -105,6 +105,7 @@
 
 class PydanticBuildContext(BaseBuildContext):
     factory_use_construct: bool
+    by_name: NotRequired[bool]
 
 
 class PydanticConstraints(Constraints):
@@ -370,6 +371,24 @@ class PaymentFactory(ModelFactory[Payment]):
     >>> payment
     Payment(amount=120, currency="EUR")
     """
+    __by_name__: ClassVar[bool] = False
+    """
+    Flag indicating whether to use model_validate with by_name parameter (Pydantic V2 only)
+
+    This helps handle validation aliases automatically without requiring users to modify their model configurations.
+
+    Example code::
+
+        class MyModel(BaseModel):
+            field_a: str = Field(..., validation_alias="special_field_a")
+
+        class MyFactory(ModelFactory[MyModel]):
+            __by_name__ = True
+
+    >>> instance = MyFactory.build(field_a="test")
+    >>> instance.field_a
+    "test"
+    """
     if not _IS_PYDANTIC_V1:
         __forward_references__: ClassVar[dict[str, Any]] = {
             # Resolve to str to avoid recursive issues
@@ -379,6 +398,7 @@ class PaymentFactory(ModelFactory[Payment]):
     __config_keys__ = (
         *BaseFactory.__config_keys__,
         "__use_examples__",
+        "__by_name__",
     )
 
     @classmethod
@@ -505,6 +525,7 @@ def build(
             kwargs["_build_context"] = PydanticBuildContext(
                 seen_models=set(),
                 factory_use_construct=factory_use_construct,
+                by_name=cls.__by_name__,
             )
 
         processed_kwargs = cls.process_kwargs(**kwargs)
@@ -538,12 +559,19 @@ def _create_model(cls, _build_context: PydanticBuildContext, **kwargs: Any) -> T
             if _is_pydantic_v1_model(cls.__model__):
                 return cls.__model__.construct(**kwargs)  # type: ignore[return-value]
             return cls.__model__.model_construct(**kwargs)
+
+        # Use model_validate with by_name for Pydantic v2 models when requested
+        if _build_context.get("by_name") and _is_pydantic_v2_model(cls.__model__):
+            return cls.__model__.model_validate(kwargs, by_name=True)  # type: ignore[return-value]
+
         return cls.__model__(**kwargs)
 
     @classmethod
     def coverage(cls, factory_use_construct: bool = False, **kwargs: Any) -> abc.Iterator[T]:
         """Build a batch of the factory's Meta.model with full coverage of the sub-types of the model.
 
+        :param factory_use_construct: A boolean that determines whether validations will be made when instantiating the
+                model. This is supported only for pydantic models.
         :param kwargs: Any kwargs. If field_meta names are set in kwargs, their values will be used.
 
         :returns: A iterator of instances of type T.
@@ -552,7 +580,9 @@ def coverage(cls, factory_use_construct: bool = False, **kwargs: Any) -> abc.Ite
 
         if "_build_context" not in kwargs:
             kwargs["_build_context"] = PydanticBuildContext(
-                seen_models=set(), factory_use_construct=factory_use_construct
+                seen_models=set(),
+                factory_use_construct=factory_use_construct,
+                by_name=cls.__by_name__,
             )
 
         for data in cls.process_kwargs_coverage(**kwargs):

tests/test_pydantic_factory.py

@@ -494,6 +494,78 @@ class MyFactory(ModelFactory):
     assert instance.aliased_field == "some"
 
 
+@pytest.mark.skipif(IS_PYDANTIC_V1, reason="pydantic 2 only test")
+def test_build_instance_with_by_name_class_variable() -> None:
+    """Test that __by_name__ class variable enables by_name for model validation."""
+    from pydantic import AliasPath
+
+    class MyModel(BaseModel):
+        field_a: str = Field(..., validation_alias="special_field_a")
+        field_b: int = Field(..., validation_alias=AliasPath("nested", "field_b"))  # type: ignore[pydantic-alias]
+
+    class MyFactory(ModelFactory):
+        __model__ = MyModel
+        __by_name__ = True
+
+    # With __by_name__ = True, the factory uses model_validate with by_name
+    instance = MyFactory.build()
+    assert isinstance(instance.field_a, str)
+    assert isinstance(instance.field_b, int)
+
+    # Can pass field names directly when __by_name__ is True
+    instance2 = MyFactory.build(field_a="test", field_b=42)
+    assert instance2.field_a == "test"
+    assert instance2.field_b == 42
+
+
+@pytest.mark.skipif(IS_PYDANTIC_V1, reason="pydantic 2 only test")
+def test_build_instance_with_by_name_and_alias_path() -> None:
+    """Test that __by_name__ class variable works with AliasPath validation aliases."""
+    from pydantic import AliasPath
+
+    class NestedModel(BaseModel):
+        value: str = Field(..., validation_alias=AliasPath("b", "a"))  # type: ignore[pydantic-alias]
+
+    class MyFactory(ModelFactory):
+        __model__ = NestedModel
+        __by_name__ = True
+
+    # Build with __by_name__ = True to handle the validation alias correctly
+    instance = MyFactory.build()
+    assert isinstance(instance.value, str)
+
+
+@pytest.mark.skipif(IS_PYDANTIC_V1, reason="pydantic 2 only test")
+def test_build_instance_with_by_name_and_factory_field_values() -> None:
+    """Test that __by_name__ class variable works with factory field value overrides."""
+    from pydantic import AliasPath
+
+    class MyModel(BaseModel):
+        field_a: str = Field(..., validation_alias="special_field_a")
+        field_b: int = Field(..., validation_alias=AliasPath("nested", "field_b"))  # type: ignore[pydantic-alias]
+        field_c: str = Field(default="default_c")
+
+    class MyFactory(ModelFactory):
+        __model__ = MyModel
+        __by_name__ = True
+
+        # Set default values on the factory
+        field_a = "factory_default_a"
+        field_c = "factory_default_c"
+
+    # Build using factory defaults
+    instance = MyFactory.build()
+    assert instance.field_a == "factory_default_a"
+    assert isinstance(instance.field_b, int)
+    assert instance.field_c == "factory_default_c"
+
+    # Override factory defaults
+    instance2 = MyFactory.build(field_a="override_a", field_b=99)
+    assert instance2.field_a == "override_a"
+    assert instance2.field_b == 99
+    assert instance2.field_c == "factory_default_c"
+
+
 def test_build_instance_by_field_name_with_allow_population_by_field_name_flag() -> None:
     class MyModel(BaseModel):
         aliased_field: str = Field(..., alias="special_field")