Only serialize used rx.Base fields

[abulvenz]

If you check the payloads when running the example below, you might notice that value is only serialized when you comment in line 43 where the value is displayed.
Fields are checked on class level, so always the union of all used fields will be serialized (Not per usage, which would be cool, but more sophisticated.)

from __future__ import annotations
import reflex as rx
from reflex.base import SlimBase


def on_frontend_exception(exception: Exception) -> None:
    pass

app: rx.App = rx.App(frontend_exception_handler=on_frontend_exception)


class SmartObjectChild(SlimBase):
    name: str = "Smart Object Child"
    value: int = 0

class SmartObject(SlimBase):
    name: str = "Smart Object"
    value: int = 0
    child: SmartObjectChild = SmartObjectChild()
    children: list[SmartObjectChild] = [SmartObjectChild(), SmartObjectChild()]

    def increment(self):
        self.value += 1

    def decrement(self):
        self.value -= 1


class LSpace(rx.State):
    computed_var: str = "Computed var"
    some_list: list[SmartObject] = [SmartObject(), SmartObject()]

    smartie: SmartObject = SmartObject()

    def set_smartie_name(self, name: str) -> None:
        self.smartie.name = name


def index() -> rx.Component:
    return rx.box(
        rx.heading("Test smart object!"),
        rx.foreach(LSpace.some_list, lambda x: rx.box(rx.text(x.name))),
       # rx.text(LSpace.smartie.value),
        rx.text(LSpace.smartie.child.name),        #rx.text(LState.smartie.child.value),

        rx.foreach(LSpace.smartie.children, lambda x: rx.box(rx.text(x.name))),


        rx.button("Decrement", on_click=LSpace.set_smartie_name("Decremented")),
        rx.button("Increment", on_click=LSpace.set_smartie_name("Incremented")),
    )

app.add_page(index)