added the new function to the const_class decorator

Author: SpectraL519

src/constclasses/const_class.py

@@ -5,6 +5,8 @@
     ConstClassBase,
 )
 
+from copy import deepcopy
+
 
 def const_class_impl(
     cls,
@@ -58,6 +60,17 @@ def __setattr__(self, attr_name: str, attr_value) -> None:
                 attr_name, cls.__annotations__.get(attr_name), attr_value
             )
 
+        def new(self, **kwargs):
+            def _get_value(key: str):
+                return kwargs.get(key, deepcopy(getattr(self, key)))
+
+            if with_kwargs:
+                init_params = {key: _get_value(key) for key in self.__annotations__}
+                return ConstClass(**init_params)
+            else:
+                init_params = [_get_value(key) for key in self.__annotations__]
+                return ConstClass(*init_params)
+
     ConstClass.__name__ = cls.__name__
     ConstClass.__module__ = cls.__module__
 

test/test_const_class.py

@@ -198,3 +198,45 @@ def _initialize():
     util.assert_does_not_throw(_initialize)
     assert const_instance.x == x_value
     assert const_instance.s == str(x_value)
+
+
+def test_new_with_kwargs():
+    @const_class(with_kwargs=True)
+    class ConstClassWithKwargs:
+        x: int
+        s: str
+
+        def __eq__(self, other: object) -> bool:
+            return isinstance(other, self.__class__) and other.x == self.x and other.s == self.s
+
+    const_instance = ConstClassWithKwargs(**ATTR_VALS_1)
+
+    # should create an exact copy by default
+    const_instance_new_default = const_instance.new()
+    assert const_instance_new_default == const_instance
+
+    const_instance_new = const_instance.new(x=ATTR_VALS_2[X_ATTR_NAME])
+    assert isinstance(const_instance_new, ConstClassWithKwargs)
+    assert const_instance_new.s == const_instance.s
+    assert const_instance_new.x == ATTR_VALS_2[X_ATTR_NAME]
+
+
+def test_new_with_args():
+    @const_class(with_kwargs=False)
+    class ConstClassWithKwargs:
+        x: int
+        s: str
+
+        def __eq__(self, other: object) -> bool:
+            return isinstance(other, self.__class__) and other.x == self.x and other.s == self.s
+
+    const_instance = ConstClassWithKwargs(*(ATTR_VALS_1.values()))
+
+    # should create an exact copy by default
+    const_instance_new_default = const_instance.new()
+    assert const_instance_new_default == const_instance
+
+    const_instance_new = const_instance.new(x=ATTR_VALS_2[X_ATTR_NAME])
+    assert isinstance(const_instance_new, ConstClassWithKwargs)
+    assert const_instance_new.s == const_instance.s
+    assert const_instance_new.x == ATTR_VALS_2[X_ATTR_NAME]