add setter support (#11)

* add setter support

* some more tests

* add some random chatgpt tests

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* add type hints

* test against python 3.13

* test non-dataclass behaviour

* test setter only

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

.github/workflows/pytest.yaml

@@ -15,6 +15,7 @@ jobs:
       fail-fast: false
       matrix:
         python-version:
+          - "3.13"
           - "3.12"
           - "3.11"
           - "3.10"

README.md

@@ -4,7 +4,8 @@
 
 # znfields
 
-Provide a `getter` for `dataclasses.fields` to allow e.g. for lazy evaluation.
+Provide a `getter` and `setter` for `dataclasses.fields` to allow e.g. for lazy
+evaluation or field content validation.
 
 ```bash
 pip install znfields
@@ -19,10 +20,15 @@ additional `getter` argument.
 import dataclasses
 import znfields
 
-def parameter_getter(self, name):
+def getter(self, name) -> str:
     return f"{name}:{self.__dict__[name]}"
 
+def setter(self, name, value) -> None:
+    if not isinstance(value, float):
+        raise ValueError(f"Value {value} is not a float")
+    self.__dict__[name] = value
+
 @dataclasses.dataclass
-class ClassWithParameter(znfields.Base):
-    parameter: float = znfields.field(getter=parameter_getter)
+class MyModel(znfields.Base):
+    parameter: float = znfields.field(getter=getter, setter=setter)
 ```

tests/test_readme.py

@@ -0,0 +1,27 @@
+import dataclasses
+
+import pytest
+
+import znfields
+
+
+def getter(self, name):
+    return f"{name}:{self.__dict__[name]}"
+
+
+def setter(self, name, value):
+    if not isinstance(value, float):
+        raise ValueError(f"Value {value} is not a float")
+    self.__dict__[name] = value
+
+
+@dataclasses.dataclass
+class MyModel(znfields.Base):
+    parameter: float = znfields.field(getter=getter, setter=setter)
+
+
+def test_readme():
+    model = MyModel(parameter=3.14)
+    assert model.parameter == "parameter:3.14"
+    with pytest.raises(ValueError):
+        model.parameter = 42

tests/test_znfields.py

@@ -5,32 +5,52 @@
 import znfields
 
 
-def example1_parameter_getter(self, name):
+def getter_01(self, name):
     return f"{name}:{self.__dict__[name]}"
 
 
+def setter_01(self, name, value):
+    if not isinstance(value, float):
+        raise ValueError(f"Value {value} is not a float")
+    self.__dict__[name] = value
+
+
 def stringify_list(self, name):
     content = self.__dict__[name]
     self.__dict__[name] = [str(x) for x in content]
     # Can not return a copy to append to, but must be the same object
     return self.__dict__[name]
 
 
+@dataclasses.dataclass
+class SetterGetterNoInit(znfields.Base):
+    parameter: float = znfields.field(getter=getter_01, setter=setter_01, init=False)
+
+
+@dataclasses.dataclass
+class SetterOnly(znfields.Base):
+    parameter: float = znfields.field(setter=setter_01)
+
+
 @dataclasses.dataclass
 class Example1(znfields.Base):
-    parameter: float = znfields.field(getter=example1_parameter_getter)
+    parameter: float = znfields.field(getter=getter_01)
 
 
 @dataclasses.dataclass
 class Example1WithDefault(znfields.Base):
-    parameter: float = znfields.field(getter=example1_parameter_getter, default=1)
+    parameter: float = znfields.field(getter=getter_01, default=1)
 
 
 @dataclasses.dataclass
 class Example1WithDefaultFactory(znfields.Base):
     parameter: list = znfields.field(getter=stringify_list, default_factory=list)
 
 
+class NoDataClass(znfields.Base):
+    parameter: float = znfields.field(getter=getter_01, setter=setter_01)
+
+
 def test_example1():
     example = Example1(parameter=1)
     assert example.parameter == "parameter:1"
@@ -58,14 +78,15 @@ def test_example2():
 
 def test_wrong_metadata():
     with pytest.raises(TypeError):
-        znfields.field(getter=example1_parameter_getter, metadata="Hello")
+        znfields.field(getter=getter_01, metadata="Hello")
+
+    with pytest.raises(TypeError):
+        znfields.field(setter=setter_01, metadata="Hello")
 
 
 @dataclasses.dataclass
 class Example3(znfields.Base):
-    parameter: float = znfields.field(
-        getter=example1_parameter_getter, metadata={"category": "test"}
-    )
+    parameter: float = znfields.field(getter=getter_01, metadata={"category": "test"})
 
 
 def test_example3():
@@ -75,7 +96,7 @@ def test_example3():
     field = dataclasses.fields(example)[0]
     assert field.metadata == {
         "category": "test",
-        znfields.ZNFIELDS_GETTER_TYPE: example1_parameter_getter,
+        znfields.ZNFIELDS_GETTER_TYPE: getter_01,
     }
 
 
@@ -154,3 +175,104 @@ def test_default_factory():
     assert example.parameter == []
     example.parameter.append(1)
     assert example.parameter == ["1"]
+
+
+def test_getter_setter_no_init():
+    example = SetterGetterNoInit()
+    with pytest.raises(ValueError):
+        example.parameter = "text"
+
+    example.parameter = 3.14
+    assert example.parameter == "parameter:3.14"
+
+    # test non-field attributes
+    example.some_attribute = 42
+    assert example.some_attribute == 42
+
+
+@dataclasses.dataclass
+class ParentClass(znfields.Base):
+    parent_field: str = znfields.field(getter=getter_01)
+
+
+@dataclasses.dataclass
+class ChildClass(ParentClass):
+    child_field: str = znfields.field(getter=getter_01)
+
+
+def test_inherited_getter():
+    instance = ChildClass(parent_field="parent", child_field="child")
+    assert instance.parent_field == "parent_field:parent"
+    assert instance.child_field == "child_field:child"
+
+
+def test_setter_validation():
+    example = SetterGetterNoInit()
+
+    with pytest.raises(ValueError):
+        example.parameter = "invalid value"
+
+    with pytest.raises(KeyError):
+        # dict is not set, getter raises KeyError instead of AttributeError
+        assert example.parameter is None
+
+    example.parameter = 2.71
+    assert example.parameter == "parameter:2.71"
+
+
+@dataclasses.dataclass
+class NoDefaultField(znfields.Base):
+    parameter: float = znfields.field(getter=getter_01, setter=setter_01)
+
+
+def test_no_default_field():
+    with pytest.raises(TypeError):
+        NoDefaultField()  # should raise because no default is provided
+    obj = NoDefaultField(parameter=1.23)
+    assert obj.parameter == "parameter:1.23"
+
+
+@dataclasses.dataclass
+class CombinedGetterSetter(znfields.Base):
+    parameter: float = znfields.field(getter=getter_01, setter=setter_01)
+
+
+def test_combined_getter_setter():
+    obj = CombinedGetterSetter(parameter=2.5)
+    assert obj.parameter == "parameter:2.5"
+    obj.parameter = 3.5
+    assert obj.parameter == "parameter:3.5"
+
+    with pytest.raises(ValueError):
+        obj.parameter = "invalid value"
+
+
+@dataclasses.dataclass
+class Nested(znfields.Base):
+    inner_field: float = znfields.field(getter=getter_01)
+
+
+@dataclasses.dataclass
+class Outer(znfields.Base):
+    outer_field: Nested = dataclasses.field(default_factory=lambda: Nested(1.0))
+
+
+def test_nested_dataclass():
+    obj = Outer()
+    assert obj.outer_field.inner_field == "inner_field:1.0"
+
+
+def test_no_dataclass():
+    x = NoDataClass()
+    with pytest.raises(TypeError, match="is not a dataclass"):
+        x.parameter = 5
+
+    with pytest.raises(TypeError, match="is not a dataclass"):
+        assert x.parameter is None
+
+
+def test_setter_only():
+    x = SetterOnly(parameter=5.5)
+    with pytest.raises(ValueError):
+        x.parameter = "5"
+    assert x.parameter == 5.5

znfields/__init__.py

@@ -4,14 +4,45 @@
 
 
 class _ZNFIELDS_GETTER_TYPE:
+    """Sentinel class to identify the getter type."""
+
+    pass
+
+
+class _ZNFIELDS_SETTER_TYPE:
+    """Sentinel class used to identify the setter type."""
+
     pass
 
 
+# Sentinels to identify the getter and setter types
 ZNFIELDS_GETTER_TYPE = _ZNFIELDS_GETTER_TYPE()
+ZNFIELDS_SETTER_TYPE = _ZNFIELDS_SETTER_TYPE()
 
 
 class Base:
+    """Base class to extend dataclasses with custom getter and setter behavior
+    through field metadata.
+
+    Methods
+    -------
+    __getattribute__(name: str) -> Any
+        Overrides the default behavior of attribute access to allow for
+        custom getter functionality defined via field metadata.
+    __setattr__(name: str, value: Any) -> None
+        Overrides the default behavior of attribute assignment to allow for
+        custom setter functionality defined via field metadata.
+    """
+
     def __getattribute__(self, name: str) -> Any:
+        """Overrides the default behavior of attribute access.
+
+        Allow for custom getter functionality defined via field metadata.
+
+        Raises
+        ------
+        TypeError: If the class is not a dataclass.
+        """
         if name.startswith("__") and name.endswith("__"):
             return super().__getattribute__(name)
         if not dataclasses.is_dataclass(self):
@@ -27,11 +58,59 @@ def __getattribute__(self, name: str) -> Any:
             return lazy(self, name)
         return super().__getattribute__(name)
 
+    def __setattr__(self, name: str, value: Any) -> None:
+        """Overrides the default behavior of attribute assignment.
+
+        Allow for custom setter functionality defined via field metadata.
+
+        Raises
+        ------
+        TypeError: If the class is not a dataclass.
+        """
+        if not dataclasses.is_dataclass(self):
+            raise TypeError(f"{self} is not a dataclass")
+        try:
+            field = next(
+                field for field in dataclasses.fields(self) if field.name == name
+            )
+        except StopIteration:
+            return super().__setattr__(name, value)
+        setter = field.metadata.get(ZNFIELDS_SETTER_TYPE)
+        if setter:
+            setter(self, name, value)
+        else:
+            super().__setattr__(name, value)
+
 
 @functools.wraps(dataclasses.field)
 def field(
-    *, getter: Optional[Callable[[Any, str], Any]] = None, **kwargs
+    *,
+    getter: Optional[Callable[[Any, str], Any]] = None,
+    setter: Optional[Callable[[Any, str, Any], None]] = None,
+    **kwargs,
 ) -> dataclasses.Field:
+    """Wrapper around `dataclasses.field` to allow for defining custom
+    getter and setter functions via metadata.
+
+    Attributes
+    ----------
+    getter : Optional[Callable[[Any, str], Any]]
+        A function that takes the instance and attribute name as arguments
+        and returns the value of the attribute.
+    setter : Optional[Callable[[Any, str, Any], None]]
+        A function that takes the instance, attribute name, and value as
+        arguments and sets the value of the attribute.
+
+    Returns
+    -------
+    dataclasses.Field
+        A field object with custom getter and setter functionality defined
+        via metadata.
+
+    Raises
+    ------
+    TypeError: If the metadata is not a dictionary.
+    """
     if getter is not None:
         if "metadata" in kwargs:
             if not isinstance(kwargs["metadata"], dict):
@@ -41,4 +120,13 @@ def field(
             kwargs["metadata"][ZNFIELDS_GETTER_TYPE] = getter
         else:
             kwargs["metadata"] = {ZNFIELDS_GETTER_TYPE: getter}
+    if setter is not None:
+        if "metadata" in kwargs:
+            if not isinstance(kwargs["metadata"], dict):
+                raise TypeError(
+                    f"metadata must be a dict, not {type(kwargs['metadata'])}"
+                )
+            kwargs["metadata"][ZNFIELDS_SETTER_TYPE] = setter
+        else:
+            kwargs["metadata"] = {ZNFIELDS_SETTER_TYPE: setter}
     return dataclasses.field(**kwargs)