bug: `AssertionError: assert self.__uid is not None`

[ndonkoHenri]

Duplicate Check

• I have searched the opened issues and there are no duplicates

Describe the bug

An assertion error is raised when running the attached code.

Code sample

Code

import time
import flet as ft


class ChatMessage(ft.Row):
    def __init__(self, message: str):
        super().__init__()
        self.controls = [ft.CircleAvatar(content=ft.Text("U")), ft.Text(message)]


def main(page: ft.Page):
    def on_message(message: str):
        chat.controls.append(ChatMessage(message))
        page.update()

    page.pubsub.subscribe(on_message)

    chat = ft.ListView(
        expand=True,
        auto_scroll=True,
    )

    page.add(chat)
    for i in range(300):
        page.pubsub.send_all(f"message {i}")
        time.sleep(0.2)


ft.app(target=main)

To reproduce

Run the code, then wait for some time while observing the terminal.

Expected behavior

No response

Screenshots / Videos

Captures

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Operating System

macOS

Operating system details

15.0

Flet version

0.26.0

Regression

I'm not sure / I don't know

Suggestions

No response

Logs

Logs

Traceback (most recent call last):
  File "/Library/Frameworks/Python.framework/Versions/3.12/lib/python3.12/concurrent/futures/thread.py", line 58, in run
    result = self.fn(*self.args, **self.kwargs)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/ndonkohenri/PycharmProjects/flet-dev/flet/sdk/python/playground/test-b.py", line 15, in on_message
  File "/Users/ndonkohenri/PycharmProjects/flet-dev/flet/sdk/python/packages/flet/src/flet/core/page.py", line 732, in update
    r = self.__update(self)
        ^^^^^^^^^^^^^^^^^^^
  File "/Users/ndonkohenri/PycharmProjects/flet-dev/flet/sdk/python/packages/flet/src/flet/core/page.py", line 798, in __update
    commands, added_controls, removed_controls = self.__prepare_update(*controls)
                                                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/ndonkohenri/PycharmProjects/flet-dev/flet/sdk/python/packages/flet/src/flet/core/page.py", line 814, in __prepare_update
    control.build_update_commands(
  File "/Users/ndonkohenri/PycharmProjects/flet-dev/flet/sdk/python/packages/flet/src/flet/core/control.py", line 483, in build_update_commands
    ctrl.build_update_commands(
  File "/Users/ndonkohenri/PycharmProjects/flet-dev/flet/sdk/python/packages/flet/src/flet/core/control.py", line 483, in build_update_commands
    ctrl.build_update_commands(
  File "/Users/ndonkohenri/PycharmProjects/flet-dev/flet/sdk/python/packages/flet/src/flet/core/control.py", line 483, in build_update_commands
    ctrl.build_update_commands(
  File "/Users/ndonkohenri/PycharmProjects/flet-dev/flet/sdk/python/packages/flet/src/flet/core/control.py", line 502, in build_update_commands
    assert self.__uid is not None
           ^^^^^^^^^^^^^^^^^^^^^^
AssertionError
Future exception was never retrieved
future: <Future finished exception=AssertionError()>
Traceback (most recent call last):
  File "/Library/Frameworks/Python.framework/Versions/3.12/lib/python3.12/concurrent/futures/thread.py", line 58, in run
    result = self.fn(*self.args, **self.kwargs)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/ndonkohenri/PycharmProjects/flet-dev/flet/sdk/python/playground/test-b.py", line 15, in on_message
  File "/Users/ndonkohenri/PycharmProjects/flet-dev/flet/sdk/python/packages/flet/src/flet/core/page.py", line 732, in update
    r = self.__update(self)
        ^^^^^^^^^^^^^^^^^^^
  File "/Users/ndonkohenri/PycharmProjects/flet-dev/flet/sdk/python/packages/flet/src/flet/core/page.py", line 798, in __update
    commands, added_controls, removed_controls = self.__prepare_update(*controls)
                                                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/ndonkohenri/PycharmProjects/flet-dev/flet/sdk/python/packages/flet/src/flet/core/page.py", line 814, in __prepare_update
    control.build_update_commands(
  File "/Users/ndonkohenri/PycharmProjects/flet-dev/flet/sdk/python/packages/flet/src/flet/core/control.py", line 483, in build_update_commands
    ctrl.build_update_commands(
  File "/Users/ndonkohenri/PycharmProjects/flet-dev/flet/sdk/python/packages/flet/src/flet/core/control.py", line 483, in build_update_commands
    ctrl.build_update_commands(
  File "/Users/ndonkohenri/PycharmProjects/flet-dev/flet/sdk/python/packages/flet/src/flet/core/control.py", line 483, in build_update_commands
    ctrl.build_update_commands(
  File "/Users/ndonkohenri/PycharmProjects/flet-dev/flet/sdk/python/packages/flet/src/flet/core/control.py", line 502, in build_update_commands
    assert self.__uid is not None

Additional details

Issue happens occasionally but very often.

[HappyCoder256]

I used to get this error and as am talking right now, I still run into it but the only temporary fix I discovered for it is to decrease on the consistent rates where your app's ui is updated or reduce on calling page.update consistently.

[omamkaz]

try to remove page.update() from on_message method!

[ndonkoHenri]

try to remove page.update() from on_message method!

The UI won't get updated in that case. 😅

[HappyCoder256]

Try increasing the sleep value to something like 0.6. U'll not run into that error. The only reason why ure getting assertion is because you're trying to update the app's ui At the fastest rate in the way that the app is requesting a ui update even before completing the previous ui update request.