Deepcopy

README.md

@@ -124,6 +124,46 @@ print(vars(public_user_info))
 # {'full_name': 'John Cusack', 'profession': 'engineer'}
 ```
 
+## Use of Deepcopy
+By default, automapper performs a recursive deepcopy() on all attributes. This makes sure that changes in the attributes of the source
+do not affect the target and vice-versa:
+
+```python
+from dataclasses import dataclass
+from automapper import mapper
+
+@dataclass
+class Address:
+  street: str
+  number: int
+  zip_code: int
+  city: str
+
+class PersonInfo:
+    def __init__(self, name: str, age: int, address: Address):
+        self.name = name
+        self.age = age
+        self.address = address
+
+class PublicPersonInfo:
+    def __init__(self, name: str, address: Address):
+        self.name = name
+        self.address = address
+
+address = Address(street="Main Street", number=1, zip_code=100001, city='Test City')
+info = PersonInfo('John Doe', age=35, address=address)
+
+public_info = mapper.to(PublicPersonInfo).map(info)
+assert address is not public_info.address
+```
+
+To disable this behavior, you may pass `deepcopy=False` to either `mapper.map()` or to `mapper.add()`. If both are passed,
+the argument of the `.map()` call has priority. E.g.
+
+```python
+public_info = mapper.to(PublicPersonInfo).map(info, deepcopy=False)
+assert address is public_info.address
+```
 
 ## Extensions
 `py-automapper` has few predefined extensions for mapping support to classes for frameworks:

automapper/exceptions.py

@@ -8,6 +8,4 @@ class MappingError(Exception):
 
 class CircularReferenceError(Exception):
     def __init__(self, *args: object) -> None:
-        super().__init__(
-            "Mapper does not support objects with circular references yet", *args
-        )
+        super().__init__("Mapper does not support objects with circular references yet", *args)

automapper/extensions/default.py

@@ -11,9 +11,7 @@ def __init_method_classifier__(target_cls: Type[T]) -> bool:
     return (
         hasattr(target_cls, "__init__")
         and hasattr(getattr(target_cls, "__init__"), "__annotations__")
-        and isinstance(
-            getattr(getattr(target_cls, "__init__"), "__annotations__"), dict
-        )
+        and isinstance(getattr(getattr(target_cls, "__init__"), "__annotations__"), dict)
         and getattr(getattr(target_cls, "__init__"), "__annotations__")
     )
 

automapper/mapper.py

@@ -65,26 +65,29 @@ def map(
         *,
         skip_none_values: bool = False,
         fields_mapping: FieldsMap = None,
+        deepcopy: bool = True,
     ) -> T:
         """Produces output object mapped from source object and custom arguments
 
         Parameters:
             skip_none_values - do not map fields that has None value
             fields_mapping - mapping for fields with different names
+            deepcopy - should we deepcopy all attributes? [default: True]
         """
         return self.__mapper._map_common(
             obj,
             self.__target_cls,
             set(),
             skip_none_values=skip_none_values,
             fields_mapping=fields_mapping,
+            deepcopy=deepcopy,
         )
 
 
 class Mapper:
     def __init__(self) -> None:
         """Initializes internal containers"""
-        self._mappings: Dict[Type[S], Tuple[T, FieldsMap]] = {}  # type: ignore [valid-type]
+        self._mappings: Dict[Type[S], Tuple[T, FieldsMap, bool]] = {}  # type: ignore [valid-type]
         self._class_specs: Dict[Type[T], SpecFunction[T]] = {}  # type: ignore [valid-type]
         self._classifier_specs: Dict[  # type: ignore [valid-type]
             ClassifierFunction[T], SpecFunction[T]
@@ -102,9 +105,7 @@ def add_spec(self, classifier: Type[T], spec_func: SpecFunction[T]) -> None:
         ...
 
     @overload
-    def add_spec(
-        self, classifier: ClassifierFunction[T], spec_func: SpecFunction[T]
-    ) -> None:
+    def add_spec(self, classifier: ClassifierFunction[T], spec_func: SpecFunction[T]) -> None:
         """Add a spec function for all classes identified by classifier function.
 
         Parameters:
@@ -141,6 +142,7 @@ def add(
         target_cls: Type[T],
         override: bool = False,
         fields_mapping: FieldsMap = None,
+        deepcopy: bool = True,
     ) -> None:
         """Adds mapping between object of `source class` to an object of `target class`.
 
@@ -152,35 +154,37 @@ def add(
             Target class to map to
         override : bool, optional
             Override existing `source class` mapping to use new `target class`
+        deepcopy : bool, optional
+            Should we deepcopy all attributes? [default: True]
         """
         if source_cls in self._mappings and not override:
             raise DuplicatedRegistrationError(
                 f"source_cls {source_cls} was already added for mapping"
             )
-        self._mappings[source_cls] = (target_cls, fields_mapping)
+        self._mappings[source_cls] = (target_cls, fields_mapping, deepcopy)
 
     def map(
         self,
         obj: object,
         *,
         skip_none_values: bool = False,
         fields_mapping: FieldsMap = None,
+        deepcopy: bool = None,
     ) -> T:  # type: ignore [type-var]
         """Produces output object mapped from source object and custom arguments"""
         obj_type = type(obj)
         if obj_type not in self._mappings:
             raise MappingError(f"Missing mapping type for input type {obj_type}")
         obj_type_preffix = f"{obj_type.__name__}."
 
-        target_cls, target_cls_field_mappings = self._mappings[obj_type]
+        target_cls, target_cls_field_mappings, target_deepcopy = self._mappings[obj_type]
 
         common_fields_mapping = fields_mapping
         if target_cls_field_mappings:
             # transform mapping if it's from source class field
             common_fields_mapping = {
                 target_obj_field: getattr(obj, source_field[len(obj_type_preffix) :])
-                if isinstance(source_field, str)
-                and source_field.startswith(obj_type_preffix)
+                if isinstance(source_field, str) and source_field.startswith(obj_type_preffix)
                 else source_field
                 for target_obj_field, source_field in target_cls_field_mappings.items()
             }
@@ -190,12 +194,17 @@ def map(
                     **fields_mapping,
                 }  # merge two dict into one, fields_mapping has priority
 
+        # If deepcopy is not explicitly given, we use target_deepcopy
+        if deepcopy is None:
+            deepcopy = target_deepcopy
+
         return self._map_common(
             obj,
             target_cls,
             set(),
             skip_none_values=skip_none_values,
             fields_mapping=common_fields_mapping,
+            deepcopy=deepcopy,
         )
 
     def _get_fields(self, target_cls: Type[T]) -> Iterable[str]:
@@ -208,9 +217,7 @@ def _get_fields(self, target_cls: Type[T]) -> Iterable[str]:
             if classifier(target_cls):
                 return self._classifier_specs[classifier](target_cls)
 
-        raise MappingError(
-            f"No spec function is added for base class of {type(target_cls)}"
-        )
+        raise MappingError(f"No spec function is added for base class of {type(target_cls)}")
 
     def _map_subobject(
         self, obj: S, _visited_stack: Set[int], skip_none_values: bool = False
@@ -224,7 +231,7 @@ def _map_subobject(
             raise CircularReferenceError()
 
         if type(obj) in self._mappings:
-            target_cls, _ = self._mappings[type(obj)]
+            target_cls, _, _ = self._mappings[type(obj)]
             result: Any = self._map_common(
                 obj, target_cls, _visited_stack, skip_none_values=skip_none_values
             )
@@ -234,9 +241,7 @@ def _map_subobject(
             if is_sequence(obj):
                 if isinstance(obj, dict):
                     result = {
-                        k: self._map_subobject(
-                            v, _visited_stack, skip_none_values=skip_none_values
-                        )
+                        k: self._map_subobject(v, _visited_stack, skip_none_values=skip_none_values)
                         for k, v in obj.items()
                     }
                 else:
@@ -262,12 +267,14 @@ def _map_common(
         _visited_stack: Set[int],
         skip_none_values: bool = False,
         fields_mapping: FieldsMap = None,
+        deepcopy: bool = True,
     ) -> T:
         """Produces output object mapped from source object and custom arguments
 
         Parameters:
             skip_none_values - do not map fields that has None value
             fields_mapping - fields mappings for fields with different names
+            deepcopy - Should we deepcopy all attributes? [default: True]
         """
         obj_id = id(obj)
 
@@ -293,9 +300,14 @@ def _map_common(
                     value = obj[field_name]  # type: ignore [index]
 
                 if value is not None:
-                    mapped_values[field_name] = self._map_subobject(
-                        value, _visited_stack, skip_none_values
-                    )
+                    if deepcopy:
+                        mapped_values[field_name] = self._map_subobject(
+                            value, _visited_stack, skip_none_values
+                        )
+                    else:
+                        # if deepcopy is disabled, we can act as if value was a primitive type and
+                        # avoid the ._map_subobject() call entirely.
+                        mapped_values[field_name] = value
                 elif not skip_none_values:
                     mapped_values[field_name] = None
 

tests/test_automapper.py

@@ -20,9 +20,7 @@ def __init__(self, num: int, text: str, flag: bool) -> None:
 
     @classmethod
     def fields(cls) -> Iterable[str]:
-        return (
-            field for field in cls.__init__.__annotations__.keys() if field != "return"
-        )
+        return (field for field in cls.__init__.__annotations__.keys() if field != "return")
 
 
 class AnotherClass:
@@ -68,16 +66,12 @@ def setUp(self):
     def test_add_spec__adds_to_internal_collection(self):
         self.mapper.add_spec(ParentClass, custom_spec_func)
         assert ParentClass in self.mapper._class_specs
-        assert ["num", "text", "flag"] == self.mapper._class_specs[ParentClass](
-            ChildClass
-        )
+        assert ["num", "text", "flag"] == self.mapper._class_specs[ParentClass](ChildClass)
 
     def test_add_spec__error_on_adding_same_class_spec(self):
         self.mapper.add_spec(ParentClass, custom_spec_func)
         with pytest.raises(DuplicatedRegistrationError):
-            self.mapper.add_spec(
-                ParentClass, lambda concrete_type: ["field1", "field2"]
-            )
+            self.mapper.add_spec(ParentClass, lambda concrete_type: ["field1", "field2"])
 
     def test_add_spec__adds_to_internal_collection_for_classifier(self):
         self.mapper.add_spec(classifier_func, spec_func)

tests/test_automapper_dict_field.py

@@ -1,7 +1,7 @@
-from copy import deepcopy
 from typing import Any, Dict
+from unittest import TestCase
 
-from automapper import mapper
+from automapper import mapper, create_mapper
 
 
 class Candy:
@@ -12,36 +12,64 @@ def __init__(self, name: str, brand: str):
 
 class Shop:
     def __init__(self, products: Dict[str, Any], annual_income: int):
-        self.products: Dict[str, Any] = deepcopy(products)
+        self.products: Dict[str, Any] = products
         self.annual_income = annual_income
 
 
 class ShopPublicInfo:
     def __init__(self, products: Dict[str, Any]):
-        self.products: Dict[str, Any] = deepcopy(products)
+        self.products: Dict[str, Any] = products
 
 
-def test_map__with_dict_field():
-    products = {
-        "magazines": ["Forbes", "Time", "The New Yorker"],
-        "candies": [
-            Candy("Reese's cups", "The Hershey Company"),
-            Candy("Snickers", "Mars, Incorporated"),
-        ],
-    }
-    shop = Shop(products=products, annual_income=10000000)
+class AutomapperTest(TestCase):
+    def setUp(self) -> None:
+        products = {
+            "magazines": ["Forbes", "Time", "The New Yorker"],
+            "candies": [
+                Candy("Reese's cups", "The Hershey Company"),
+                Candy("Snickers", "Mars, Incorporated"),
+            ],
+        }
+        self.shop = Shop(products=products, annual_income=10000000)
+        self.mapper = create_mapper()
 
-    public_info = mapper.to(ShopPublicInfo).map(shop)
+    def test_map__with_dict_field(self):
+        public_info = mapper.to(ShopPublicInfo).map(self.shop)
 
-    assert public_info.products["magazines"] == shop.products["magazines"]
-    assert id(public_info.products["magazines"]) != id(shop.products["magazines"])
+        self.assertEqual(public_info.products["magazines"], self.shop.products["magazines"])
+        self.assertNotEqual(
+            id(public_info.products["magazines"]), id(self.shop.products["magazines"])
+        )
 
-    assert public_info.products["candies"] != shop.products["candies"]
-    assert public_info.products["candies"][0] != shop.products["candies"][0]
-    assert public_info.products["candies"][1] != shop.products["candies"][1]
+        self.assertNotEqual(public_info.products["candies"], self.shop.products["candies"])
+        self.assertNotEqual(public_info.products["candies"][0], self.shop.products["candies"][0])
+        self.assertNotEqual(public_info.products["candies"][1], self.shop.products["candies"][1])
 
-    assert public_info.products["candies"][0].name == "Reese's cups"
-    assert public_info.products["candies"][0].brand == "The Hershey Company"
+        self.assertEqual(public_info.products["candies"][0].name, "Reese's cups")
+        self.assertEqual(public_info.products["candies"][0].brand, "The Hershey Company")
 
-    assert public_info.products["candies"][1].name == "Snickers"
-    assert public_info.products["candies"][1].brand == "Mars, Incorporated"
+        self.assertEqual(public_info.products["candies"][1].name, "Snickers")
+        self.assertEqual(public_info.products["candies"][1].brand, "Mars, Incorporated")
+
+    def test_deepcopy_disabled(self):
+        public_info_deep = mapper.to(ShopPublicInfo).map(self.shop, deepcopy=False)
+        public_info = mapper.to(ShopPublicInfo).map(self.shop)
+
+        self.assertIsNot(public_info.products, self.shop.products)
+        self.assertEqual(public_info.products["magazines"], self.shop.products["magazines"])
+        self.assertNotEqual(public_info.products["magazines"], id(self.shop.products["magazines"]))
+
+        self.assertIs(public_info_deep.products, self.shop.products)
+        self.assertEqual(
+            id(public_info_deep.products["magazines"]), id(self.shop.products["magazines"])
+        )
+
+    def test_deepcopy_disabled_in_add(self):
+        self.mapper.add(Shop, ShopPublicInfo, deepcopy=False)
+        public_info = self.mapper.map(self.shop)
+
+        self.assertIs(public_info.products, self.shop.products)
+
+        # Manually enable deepcopy on .map()
+        public_info = self.mapper.map(self.shop, deepcopy=True)
+        self.assertIsNot(public_info.products, self.shop.products)