perf(descriptor): use weakref

refuse weak reference to a value in WeakRefDict instead of polluting instance namespace

aiogram/utils/helper.py

@@ -15,6 +15,7 @@ Example:
 """
 import inspect
 from typing import Any, Callable, Generic, Iterable, List, Optional, TypeVar, Union, cast
+from weakref import WeakKeyDictionary
 
 T = TypeVar("T")
 
@@ -239,56 +240,37 @@ class OrderedHelper(Helper, metaclass=OrderedHelperMeta):
 
 class DefaultProperty(Generic[T]):
     """
-    Implements descriptor. Intended to be used as a class attribute and only internally.
+    Descriptor that holds default value and for a class and
+
+    Intended to be used as a class attribute and only internally.
     """
 
-    __slots__ = (
-        "name_resolver",
-        "name",
-        "fget",
-    )
+    __slots__ = "fget", "_descriptor_instances"
 
     def __init__(
-        self,
-        default: Optional[T] = None,
-        *,
-        name_resolver: Callable[[str], str] = lambda s: "_" + s,
-        fget: Optional[Callable[[Any], T]] = None,
+        self, default: Optional[T] = None, *, fget: Optional[Callable[[Any], T]] = None,
     ) -> None:
-        if fget is None is default:
-            raise ValueError("Either default or fget should be passed.")
-
         self.fget = fget or (lambda _: cast(T, default))
-        self.name_resolver = name_resolver
-        self.name: Optional[str] = None
-
-    def __set_name__(self, owner: Any, name: str) -> None:
-        self.name = self.name_resolver(name)
-
-    def _raise_if_name_never_set(self, instance: Any) -> None:
-        if self.name is None:
-            raise AttributeError(f"Name for descriptor was never set in {instance}")
+        self._descriptor_instances = WeakKeyDictionary()  # type: ignore
 
     def __get__(self, instance: Any, owner: Any) -> T:
         if instance is None:
             return self.fget(instance)
 
-        self._raise_if_name_never_set(instance)
-
-        return cast(T, getattr(instance, self.name, self.fget(instance)))  # type: ignore
+        return self._descriptor_instances.get(instance, self.fget(instance))
 
     def __set__(self, instance: Any, value: T) -> None:
         if instance is None or isinstance(instance, type):
             raise AttributeError(
                 "Instance cannot be class or None. Setter must be called from a class."
             )
-        self._raise_if_name_never_set(instance)
-        setattr(instance, self.name, value)  # type: ignore
+
+        self._descriptor_instances[instance] = value
 
     def __delete__(self, instance: Any) -> None:
         if instance is None or isinstance(instance, type):
             raise AttributeError(
                 "Instance cannot be class or None. Deleter must be called from a class."
             )
-        self._raise_if_name_never_set(instance)
-        delattr(instance, self.name)  # type: ignore
+
+        self._descriptor_instances.pop(instance, None)

tests/test_api/test_client/test_session/test_base_session.py

@@ -49,14 +49,9 @@ class TestBaseSession:
             return json.dumps
 
         session.json_dumps = custom_dumps
-        assert session.json_dumps == custom_dumps == session._json_dumps
+        assert session.json_dumps == custom_dumps
         session.json_loads = custom_loads
-        assert session.json_loads == custom_loads == session._json_loads
-
-        different_session = CustomSession()
-        assert all(
-            not hasattr(different_session, attr) for attr in ("_json_loads", "_json_dumps", "_api")
-        )
+        assert session.json_loads == custom_loads
 
     def test_timeout(self):
         session = CustomSession()

tests/test_utils/test_helper.py

@@ -139,7 +139,6 @@ class TestDefaultDescriptor:
         obj = type("ClassA", (), {})()
         default_x_val = "some_x"
         x = DefaultProperty(default_x_val)
-        x.__set_name__(owner=obj.__class__, name="x")
 
         # we can omit owner, usually it's just obj.__class__
         assert x.__get__(instance=obj, owner=None) == default_x_val
@@ -161,45 +160,12 @@ class TestDefaultDescriptor:
         x.__delete__(instance=obj)
         assert x.__get__(instance=obj, owner=obj.__class__) == default_x_val
 
-    def test_set_name(self):
-        class A:
-            x = DefaultProperty("default")
-
-        a = A()
-        assert "_x" not in vars(a)
-
-        a.x = "new value"
-        assert "_x" in vars(a)
-
-        del a.x
-        assert "_x" not in vars(a)
-
-        assert a.x == "default"
-
-        class B:
-            x = DefaultProperty("default", name_resolver=lambda name: f"_{name}_4_{name}_")
-
-        b = B()
-        b.x = ">>"
-        assert "_x_4_x_" in vars(b)
-
-        C = type("C", (), {"x": DefaultProperty("default")})
-        c = C()
-        assert c.x == "default"
-        c.x = "new value"
-        assert "_x" in vars(c)
-
-        d = type("D", (), {})()
-        x = DefaultProperty("default")
-
-        with pytest.raises(AttributeError) as exc:
-            x.__set__(d, "new_value")
-        assert f"Name for descriptor was never set in {d}" in str(exc.value)
-
     def test_init(self):
         class A:
             x = DefaultProperty(fget=lambda a_inst: "nothing")
 
+        assert isinstance(A.__dict__["x"], DefaultProperty)
+
         a = A()
         assert a.x == "nothing"
 
@@ -207,9 +173,9 @@ class TestDefaultDescriptor:
         assert x.__get__(None, None) == "x"
         assert x.fget(None) == x.__get__(None, None)
 
-        with pytest.raises(ValueError) as exc:
+    def test_nullability(self):
+        class A:
+            x = DefaultProperty(default=None, fget=None)
 
-            class _:
-                x = DefaultProperty(default=None, fget=None)
-
-        assert "Either default or fget should be passed." in str(exc.value)
+        assert A.x is None
+        assert A().x is None