✨ feat: enable copy.replace for py3.13+

pyproject.toml

@@ -145,7 +145,9 @@ messages_control.disable = [
   "line-too-long",
   "missing-module-docstring",
   "missing-function-docstring",
+  "no-member",  # handled by mypy
   "no-value-for-parameter",  # for plum-dispatch
+  "too-many-function-args",  # handled by testing
   "unused-argument",  # handled by ruff
   "unused-wildcard-import",  # handled by ruff
   "wildcard-import",  # handled by ruff

src/dataclassish/__init__.py

@@ -19,6 +19,7 @@
     "field_items",
     # Classes
     "DataclassInstance",
+    "CanCopyReplace",
     "F",
 ]
 
@@ -33,11 +34,16 @@
     get_field,
     replace,
 )
-from ._src.types import DataclassInstance, F
+from ._src.types import CanCopyReplace, DataclassInstance, F
 from ._version import version as __version__
 
 # Register dispatches by importing the submodules
 # isort: split
-from ._src import register_base, register_dataclass, register_mapping
+from ._src import (
+    register_base,
+    register_copyreplace,
+    register_dataclass,
+    register_mapping,
+)
 
-del register_base, register_dataclass, register_mapping
+del register_base, register_dataclass, register_mapping, register_copyreplace

src/dataclassish/_src/register_base.py

@@ -2,11 +2,13 @@
 
 __all__: list[str] = []
 
+from collections.abc import Mapping
 from typing import Any, TypeVar
 
 from plum import dispatch
 
-from .api import fields
+from .api import fields, replace
+from .types import F
 
 K = TypeVar("K")
 V = TypeVar("V")
@@ -37,6 +39,20 @@ def get_field(obj: Any, k: str, /) -> Any:
     return getattr(obj, k)
 
 
+# ===================================================================
+# Replace
+
+
+def _recursive_replace_helper(obj: object, k: str, v: Any, /) -> Any:
+    if isinstance(v, F):
+        out = v.value
+    elif isinstance(v, Mapping):
+        out = replace(get_field(obj, k), v)
+    else:
+        out = v
+    return out
+
+
 # ===================================================================
 # Field keys
 

src/dataclassish/_src/register_copyreplace.py

@@ -0,0 +1,179 @@
+"""Register dispatches for CanCopyReplace objects."""
+
+__all__: list[str] = []
+
+import copy
+import sys
+from collections.abc import Mapping
+from typing import Any
+
+from plum import dispatch
+
+from .register_base import _recursive_replace_helper
+from .types import CanCopyReplace
+
+# ===================================================================
+# Get field
+
+
+@dispatch  # type: ignore[misc]
+def get_field(obj: CanCopyReplace, k: str, /) -> Any:
+    """Get a field of a dataclass instance by name.
+
+    Examples
+    --------
+    >>> from dataclasses import dataclass
+    >>> from dataclassish import get_field
+
+    % invisible-code-block: python
+    %
+    % import sys
+
+    % skip: start if(sys.version_info < (3, 13), reason="py3.13+")
+
+    >>> @dataclass
+    ... class Point:
+    ...     x: float
+    ...     y: float
+
+    >>> p = Point(1.0, 2.0)
+    >>> get_field(p, "x")
+    1.0
+
+    % skip: end
+
+    This works for any object that implements the ``__replace__`` method.
+
+    >>> class Point:
+    ...     def __init__(self, x, y):
+    ...         self.x = x
+    ...         self.y = y
+    ...     def __replace__(self, **changes):
+    ...         return Point(**(self.__dict__ | changes))
+    ...     def __repr__(self):
+    ...         return f"Point(x={self.x}, y={self.y})"
+
+    >>> p = Point(1.0, 2.0)
+    >>> get_field(p, "x")
+    1.0
+
+    """
+    return getattr(obj, k)
+
+
+# ===================================================================
+# Replace
+
+
+@dispatch
+def replace(obj: CanCopyReplace, /, **kwargs: Any) -> CanCopyReplace:
+    """Replace the fields of an object.
+
+    Examples
+    --------
+    >>> from dataclassish import replace
+
+    % invisible-code-block: python
+    %
+    % import sys
+
+    % skip: start if(sys.version_info < (3, 13), reason="py3.13+")
+
+    As of Python 3.13, dataclasses implement the ``__replace__`` method.
+
+    >>> from dataclasses import dataclass
+
+    >>> @dataclass
+    ... class Point:
+    ...     x: float
+    ...     y: float
+
+    >>> p = Point(1.0, 2.0)
+    >>> p
+    Point(x=1.0, y=2.0)
+
+    >>> replace(p, x=3.0)
+    Point(x=3.0, y=2.0)
+
+    % skip: end
+
+    >>> class Point:
+    ...     def __init__(self, x, y):
+    ...         self.x = x
+    ...         self.y = y
+    ...     def __replace__(self, **changes):
+    ...         return Point(**(self.__dict__ | changes))
+    ...     def __repr__(self):
+    ...         return f"Point(x={self.x}, y={self.y})"
+
+    >>> p = Point(1.0, 2.0)
+    >>> replace(p, x=2.0)
+    Point(x=2.0, y=2.0)
+
+    The ``__replace__`` method was introduced in Python 3.13 to bring
+    ``dataclasses.replace``-like functionality to any implementing object. The
+    method is publicly exposed via the ``copy.replace`` function.
+
+    % invisible-code-block: python
+    %
+    % import sys
+
+    % skip: start if(sys.version_info < (3, 13), reason="py3.13+")
+
+    >>> import copy
+    >>> copy.replace(p, x=3.0)
+    Point(x=3.0, y=2.0)
+
+    % skip: end
+
+    """
+    return (
+        obj.__replace__(**kwargs)
+        if sys.version_info < (3, 13)
+        else copy.replace(obj, **kwargs)
+    )
+
+
+@dispatch  # type: ignore[no-redef]
+def replace(obj: CanCopyReplace, fs: Mapping[str, Any], /) -> CanCopyReplace:
+    """Replace the fields of a dataclass instance.
+
+    Examples
+    --------
+    >>> from dataclasses import dataclass
+    >>> from dataclassish import replace, F
+
+    >>> class Point:
+    ...     def __init__(self, x, y):
+    ...         self.x = x
+    ...         self.y = y
+    ...     def __replace__(self, **changes):
+    ...         return Point(**(self.__dict__ | changes))
+    ...     def __repr__(self):
+    ...         return f"Point(x={self.x}, y={self.y})"
+
+    >>> @dataclass
+    ... class TwoPoint:
+    ...     a: Point
+    ...     b: Point
+
+    >>> p = TwoPoint(Point(1.0, 2.0), Point(3.0, 4.0))
+    >>> p
+    TwoPoint(a=Point(x=1.0, y=2.0), b=Point(x=3.0, y=4.0))
+
+    >>> replace(p, {"a": {"x": 5.0}, "b": {"y": 6.0}})
+    TwoPoint(a=Point(x=5.0, y=2.0), b=Point(x=3.0, y=6.0))
+
+    >>> replace(p, {"a": {"x": F({"thing": 5.0})}})
+    TwoPoint(a=Point(x={'thing': 5.0}, y=2.0),
+                b=Point(x=3.0, y=4.0))
+
+    This also works on mixed-type structures, e.g. a dictionary of objects.
+
+    >>> p = {"a": Point(1.0, 2.0), "b": Point(3.0, 4.0)}
+    >>> replace(p, {"a": {"x": 5.0}, "b": {"y": 6.0}})
+    {'a': Point(x=5.0, y=2.0), 'b': Point(x=3.0, y=6.0)}
+
+    """
+    kwargs = {k: _recursive_replace_helper(obj, k, v) for k, v in fs.items()}
+    return replace(obj, **kwargs)