feat: attrs integration (#503)

Adds `attrs` support into the `ResultConverter` mixin.  This enables `to_schema` and `schema_dump` to natively understand `attrs`.

Author: cofin

advanced_alchemy/service/__init__.py

@@ -22,11 +22,18 @@
 from advanced_alchemy.service._util import ResultConverter, find_filter
 from advanced_alchemy.service.pagination import OffsetPagination
 from advanced_alchemy.service.typing import (
+    ATTRS_INSTALLED,
+    AttrsInstance,
     FilterTypeT,
     ModelDictListT,
     ModelDictT,
     ModelDTOT,
     SupportedSchemaModel,
+    fields,
+    is_attrs_instance,
+    is_attrs_instance_with_field,
+    is_attrs_instance_without_field,
+    is_attrs_schema,
     is_dict,
     is_dict_with_field,
     is_dict_without_field,
@@ -47,7 +54,9 @@
 )
 
 __all__ = (
+    "ATTRS_INSTALLED",
     "DEFAULT_ERROR_MESSAGE_TEMPLATES",
+    "AttrsInstance",
     "Empty",
     "EmptyType",
     "ErrorMessages",
@@ -68,7 +77,12 @@
     "SQLAlchemySyncRepositoryReadService",
     "SQLAlchemySyncRepositoryService",
     "SupportedSchemaModel",
+    "fields",
     "find_filter",
+    "is_attrs_instance",
+    "is_attrs_instance_with_field",
+    "is_attrs_instance_without_field",
+    "is_attrs_schema",
     "is_dict",
     "is_dict_with_field",
     "is_dict_without_field",

advanced_alchemy/service/_async.py

@@ -30,6 +30,8 @@
     BulkModelDictT,
     ModelDictListT,
     ModelDictT,
+    asdict,
+    is_attrs_instance,
     is_dict,
     is_dto_data,
     is_msgspec_struct,
@@ -455,6 +457,20 @@ async def to_model(
 
         if is_dto_data(data):
             return cast("ModelT", data.create_instance())
+
+        if is_attrs_instance(data):
+            return model_from_dict(
+                model=self.model_type,
+                **asdict(data),
+            )
+
+        # Fallback for objects with __dict__ (e.g., regular classes)
+        if hasattr(data, "__dict__"):
+            return model_from_dict(
+                model=self.model_type,
+                **data.__dict__,
+            )
+
         return cast("ModelT", data)
 
     async def list_and_count(

advanced_alchemy/service/_sync.py

@@ -29,6 +29,8 @@
     BulkModelDictT,
     ModelDictListT,
     ModelDictT,
+    asdict,
+    is_attrs_instance,
     is_dict,
     is_dto_data,
     is_msgspec_struct,
@@ -454,6 +456,20 @@ def to_model(
 
         if is_dto_data(data):
             return cast("ModelT", data.create_instance())
+
+        if is_attrs_instance(data):
+            return model_from_dict(
+                model=self.model_type,
+                **asdict(data),
+            )
+
+        # Fallback for objects with __dict__ (e.g., regular classes)
+        if hasattr(data, "__dict__"):
+            return model_from_dict(
+                model=self.model_type,
+                **data.__dict__,
+            )
+
         return cast("ModelT", data)
 
     def list_and_count(

advanced_alchemy/service/_typing.py

@@ -126,16 +126,74 @@ def as_builtins(self) -> Any:
 
     LITESTAR_INSTALLED = False  # pyright: ignore[reportConstantRedefinition]
 
+try:
+    from attrs import AttrsInstance, asdict, define, field, fields, has  # pyright: ignore
+
+    ATTRS_INSTALLED = True
+except ImportError:
+
+    @runtime_checkable
+    class AttrsInstance(Protocol):  # type: ignore[no-redef]
+        """Placeholder Implementation for attrs classes"""
+
+    def asdict(*args: Any, **kwargs: Any) -> "dict[str, Any]":  # type: ignore[misc] # noqa: ARG001
+        """Placeholder implementation"""
+        return {}
+
+    def define(*args: Any, **kwargs: Any) -> Any:  # type: ignore[no-redef] # noqa: ARG001
+        """Placeholder implementation"""
+        return lambda cls: cls  # pyright: ignore[reportUnknownVariableType,reportUnknownLambdaType]
+
+    def field(*args: Any, **kwargs: Any) -> Any:  # type: ignore[no-redef] # noqa: ARG001
+        """Placeholder implementation"""
+        return None
+
+    def fields(*args: Any, **kwargs: Any) -> "tuple[Any, ...]":  # type: ignore[misc] # noqa: ARG001
+        """Placeholder implementation"""
+        return ()
+
+    def has(*args: Any, **kwargs: Any) -> bool:  # type: ignore[misc] # noqa: ARG001
+        """Placeholder implementation"""
+        return False
+
+    ATTRS_INSTALLED = False  # pyright: ignore[reportConstantRedefinition]
+
+try:
+    from cattrs import structure, unstructure  # pyright: ignore # type: ignore[import-not-found]
+
+    CATTRS_INSTALLED = True
+except ImportError:
+
+    def unstructure(*args: Any, **kwargs: Any) -> Any:  # noqa: ARG001
+        """Placeholder implementation"""
+        return {}
+
+    def structure(*args: Any, **kwargs: Any) -> Any:  # noqa: ARG001
+        """Placeholder implementation"""
+        return {}
+
+    CATTRS_INSTALLED = False  # pyright: ignore[reportConstantRedefinition]
+
 __all__ = (
+    "ATTRS_INSTALLED",
+    "CATTRS_INSTALLED",
     "LITESTAR_INSTALLED",
     "MSGSPEC_INSTALLED",
     "PYDANTIC_INSTALLED",
     "UNSET",
+    "AttrsInstance",
     "BaseModel",
     "DTOData",
     "FailFast",
     "Struct",
     "TypeAdapter",
     "UnsetType",
+    "asdict",
     "convert",
+    "define",
+    "field",
+    "fields",
+    "has",
+    "structure",
+    "unstructure",
 )