Add property support for Box

AUTHORS.rst

@@ -28,6 +28,7 @@ Code contributions:
 - Dominic (Yobmod)
 - Ivan Pepelnjak (ipspace)
 - Michał Górny (mgorny)
+- Serge Lu (Serge45)
 
 Suggestions and bug reporting:
 

box/box.py

@@ -122,6 +122,20 @@ def _get_box_config():
         "__safe_keys": {},
     }
 
+def _get_property_func(obj, key):
+    """
+    Try to get property helper functions of given object and property name.
+
+    :param obj: object to be checked for property
+    :param key: property name
+    :return: a tuple for helper functions(fget, fset, fdel). If no such property, a (None, None, None) returns
+    """
+    obj_type = type(obj)
+
+    if not hasattr(obj_type, key):
+        return None, None, None
+    attr = getattr(obj_type, key)
+    return attr.fget, attr.fset, attr.fdel
 
 class Box(dict):
     """
@@ -580,7 +594,12 @@ def __setattr__(self, key, value):
         safe_key = self._safe_attr(key)
         if safe_key in self._box_config["__safe_keys"]:
             key = self._box_config["__safe_keys"][safe_key]
-        self.__setitem__(key, value)
+
+        # if user has customized property setter, fall back to default implementation
+        if _get_property_func(self, key)[1] is not None:
+            super().__setattr__(key, value)
+        else:
+            self.__setitem__(key, value)
 
     def __delitem__(self, key):
         if self._box_config["frozen_box"]:
@@ -615,6 +634,13 @@ def __delattr__(self, item):
             raise BoxError('"_box_config" is protected')
         if item in self._protected_keys:
             raise BoxKeyError(f'Key name "{item}" is protected')
+
+        property_fdel = _get_property_func(self, item)[2]
+
+        # if user has customized property deleter, route to it
+        if property_fdel is not None:
+            property_fdel(self)
+            return
         try:
             self.__delitem__(item)
         except KeyError as err:

test/test_box.py

@@ -1355,3 +1355,33 @@ def test_box_default_not_create_on_get(self):
         assert "c" not in box2.a.b
 
         assert box2 == Box()
+
+    def test_box_property_support(self):
+        class BoxWithProperty(Box):
+            def __init__(self, *args, **kwargs):
+                super().__init__(*args, **kwargs)
+
+            @property
+            def field(self):
+                return self._field
+
+            @field.setter
+            def field(self, value):
+                self._field = value
+
+            @field.deleter
+            def field(self):
+                """
+                This is required to make `del box.field` work properly otherwise a `BoxKeyError` would be thrown.
+                """
+                del self._field
+
+        box = BoxWithProperty()
+        box.field = 5
+
+        assert 'field' not in box
+        assert '_field' in box
+        assert box.field == 5
+        assert box._field == 5
+        del box.field
+        assert not '_field' in box