add tests

reflex/utils/serializers.py

@@ -78,7 +78,7 @@ def serializer(
         )
 
     # Apply type transformation if requested
-    if to is not None:
+    if to is not None or ((to := type_hints.get("return")) is not None):
         SERIALIZER_TYPES[type_] = to
         get_serializer_type.cache_clear()
 

reflex/vars/base.py

@@ -654,8 +654,13 @@ class Var(Generic[VAR_TYPE]):
         if inspect.isclass(output):
             for var_subclass in _var_subclasses[::-1]:
                 if issubclass(output, var_subclass.var_subclass):
+                    current_var_type = self._var_type
+                    if current_var_type is Any:
+                        new_var_type = var_type
+                    else:
+                        new_var_type = var_type or current_var_type
                     to_operation_return = var_subclass.to_var_subclass.create(
-                        value=self, _var_type=var_type
+                        value=self, _var_type=new_var_type
                     )
                     return to_operation_return  # type: ignore
 

tests/units/vars/test_object.py

@@ -0,0 +1,113 @@
+from typing import assert_type, reveal_type
+
+import pytest
+
+import reflex as rx
+from reflex.utils.types import GenericType
+from reflex.vars.base import Var
+from reflex.vars.object import LiteralObjectVar, ObjectVar
+
+
+class Bare:
+    """A bare class with a single attribute."""
+
+    quantity: int = 0
+
+
+@rx.serializer
+def serialize_bare(obj: Bare) -> dict:
+    """A serializer for the bare class.
+
+    Args:
+        obj: The object to serialize.
+
+    Returns:
+        A dictionary with the quantity attribute.
+    """
+    return {"quantity": obj.quantity}
+
+
+class Base(rx.Base):
+    """A reflex base class with a single attribute."""
+
+    quantity: int = 0
+
+
+class ObjectState(rx.State):
+    """A reflex state with bare and base objects."""
+
+    bare: rx.Field[Bare] = rx.field(Bare())
+    base: rx.Field[Base] = rx.field(Base())
+
+
+@pytest.mark.parametrize("type_", [Base, Bare])
+def test_var_create(type_: GenericType) -> None:
+    my_object = type_()
+    var = Var.create(my_object)
+    assert var._var_type is type_
+
+    quantity = var.quantity
+    assert quantity._var_type is int
+
+
+@pytest.mark.parametrize("type_", [Base, Bare])
+def test_literal_create(type_: GenericType) -> None:
+    my_object = type_()
+    var = LiteralObjectVar.create(my_object)
+    assert var._var_type is type_
+
+    quantity = var.quantity
+    assert quantity._var_type is int
+
+
+@pytest.mark.parametrize("type_", [Base, Bare])
+def test_guess(type_: GenericType) -> None:
+    my_object = type_()
+    var = Var.create(my_object)
+    var = var.guess_type()
+    assert var._var_type is type_
+
+    quantity = var.quantity
+    assert quantity._var_type is int
+
+
+@pytest.mark.parametrize("type_", [Base, Bare])
+def test_state(type_: GenericType) -> None:
+    attr_name = type_.__name__.lower()
+    var = getattr(ObjectState, attr_name)
+    assert var._var_type is type_
+
+    quantity = var.quantity
+    assert quantity._var_type is int
+
+
+@pytest.mark.parametrize("type_", [Base, Bare])
+def test_state_to_operation(type_: GenericType) -> None:
+    attr_name = type_.__name__.lower()
+    original_var = getattr(ObjectState, attr_name)
+
+    var = original_var.to(ObjectVar, type_)
+    assert var._var_type is type_
+
+    var = original_var.to(ObjectVar)
+    assert var._var_type is type_
+
+
+def test_typing() -> None:
+    # Bare
+    var = ObjectState.bare.to(ObjectVar)
+    reveal_type(var)
+    _ = assert_type(var, ObjectVar[Bare])
+
+    var = ObjectState.base.to(ObjectVar, Base)
+    reveal_type(var)
+    _ = assert_type(var, ObjectVar[Base])
+
+    # Base
+    var = ObjectState.base.to(ObjectVar)
+    reveal_type(var)
+    _ = assert_type(var, ObjectVar[Base])
+
+    var = ObjectState.base.to(LiteralObjectVar, Base)
+    reveal_type(var)
+    _ = assert_type(var, LiteralObjectVar[Base])