Error when creating CheckBox with border_side.stroke_align provided as Enum

[InesaFitsner]

Duplicate Check

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

Describe the bug

It works when border_side.stroke_align is a number but returns error when it is Enum. Also, it works with Enum for Chip.

The error:

Unhandled error processing page session : Traceback (most recent call last):
  File "/Users/inesa/projects/flet-dev/flet/sdk/python/packages/flet/src/flet/app.py", line 247, in on_session_created
    await asyncio.get_running_loop().run_in_executor(
  File "/Users/inesa/.pyenv/versions/3.12.6/lib/python3.12/concurrent/futures/thread.py", line 58, in run
    result = self.fn(*self.args, **self.kwargs)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/inesa/projects/flet-dev/flet/sdk/python/playground/border_side_test.py", line 35, in main
    page.add(checkbox)
  File "/Users/inesa/projects/flet-dev/flet/sdk/python/packages/flet/src/flet/core/page.py", line 740, in add
    r = self.__update(self)
        ^^^^^^^^^^^^^^^^^^^
  File "/Users/inesa/projects/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/inesa/projects/flet-dev/flet/sdk/python/packages/flet/src/flet/core/page.py", line 814, in __prepare_update
    control.build_update_commands(
  File "/Users/inesa/projects/flet-dev/flet/sdk/python/packages/flet/src/flet/core/control.py", line 492, in build_update_commands
    innerCmds = ctrl._build_add_commands(
                ^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/inesa/projects/flet-dev/flet/sdk/python/packages/flet/src/flet/core/control.py", line 557, in _build_add_commands
    childCmd = control._build_add_commands(
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/inesa/projects/flet-dev/flet/sdk/python/packages/flet/src/flet/core/control.py", line 546, in _build_add_commands
    command = self._build_command(False)
              ^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/inesa/projects/flet-dev/flet/sdk/python/packages/flet/src/flet/core/control.py", line 573, in _build_command
    self.before_update()
  File "/Users/inesa/projects/flet-dev/flet/sdk/python/packages/flet/src/flet/core/checkbox.py", line 184, in before_update
    self._set_attr_json("borderSide", self.__border_side, wrap_attr_dict=True)
  File "/Users/inesa/projects/flet-dev/flet/sdk/python/packages/flet/src/flet/core/control.py", line 190, in _set_attr_json
    nv = self._convert_attr_json(
         ^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/inesa/projects/flet-dev/flet/sdk/python/packages/flet/src/flet/core/control.py", line 198, in _convert_attr_json
    json.dumps(value, cls=EmbedJsonEncoder, separators=(",", ":"))
  File "/Users/inesa/.pyenv/versions/3.12.6/lib/python3.12/json/__init__.py", line 238, in dumps
    **kw).encode(obj)
          ^^^^^^^^^^^
  File "/Users/inesa/projects/flet-dev/flet/sdk/python/packages/flet/src/flet/core/embed_json_encoder.py", line 59, in encode
    return super().encode(self._convert_enums(o))
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/inesa/.pyenv/versions/3.12.6/lib/python3.12/json/encoder.py", line 200, in encode
    chunks = self.iterencode(o, _one_shot=True)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/inesa/.pyenv/versions/3.12.6/lib/python3.12/json/encoder.py", line 258, in iterencode
    return _iterencode(o, 0)
           ^^^^^^^^^^^^^^^^^
  File "/Users/inesa/projects/flet-dev/flet/sdk/python/packages/flet/src/flet/core/embed_json_encoder.py", line 49, in default
    obj_as_dict = self._convert_enums(obj.__dict__)
                                      ^^^^^^^^^^^^
AttributeError: 'mappingproxy' object has no attribute '__dict__'. Did you mean: '__dir__'?

Code sample

Code

import flet as ft


def main(page: ft.Page):

    checkbox = ft.Checkbox(
        label="Checkbox label",
        value=True,
        label_position=ft.LabelPosition.LEFT,
        label_style=ft.TextStyle(size=20),
        tristate=True,
        autofocus=True,
        fill_color={
            ft.ControlState.HOVERED: ft.Colors.GREEN,
            ft.ControlState.FOCUSED: ft.Colors.RED,
            ft.ControlState.DEFAULT: ft.Colors.BLACK,
        },
        overlay_color={
            ft.ControlState.HOVERED: ft.Colors.GREEN,
            ft.ControlState.FOCUSED: ft.Colors.RED,
            ft.ControlState.DEFAULT: ft.Colors.BLACK,
        },
        check_color=ft.Colors.GREEN_800,
        active_color=ft.Colors.GREEN_200,
        hover_color=ft.Colors.AMBER_300,
        focus_color=ft.Colors.RED_200,
        semantics_label="semantics label",
        shape=ft.RoundedRectangleBorder(10),
        splash_radius=5,
        border_side=ft.BorderSide(
            width=5, color=ft.Colors.RED, stroke_align=ft.BorderSideStrokeAlign.CENTER
        ),
    )

    page.add(checkbox)


ft.app(main)

To reproduce

1. Run the repro code -> see the error in output

Expected behavior

No response

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Operating System

macOS

Operating system details

macOS

Flet version

0.25.1

Regression

No, it isn't

Suggestions

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Additional details

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