Support overridden dataclass defaults in control encoding

[FeodorFitsner]

This is how we can define custom control and their default property values:

from dataclasses import dataclass, field
from typing import Any

import flet as ft


def main(page: ft.Page):
    @ft.control
    class MyButton(ft.Button):
        expand: int = field(default_factory=lambda: 1)
        style: ft.ButtonStyle = field(
            default_factory=lambda: ft.ButtonStyle(
                shape=ft.RoundedRectangleBorder(radius=10)
            )
        )
        bgcolor: ft.Colors = ft.Colors.BLUE_ACCENT
        icon: Any = ft.Icons.HEADPHONES

    @dataclass
    class MyButton2(ft.Button):
        expand: Any = 1
        bgcolor: ft.Colors = ft.Colors.GREEN_ACCENT
        style: ft.ButtonStyle = field(
            default_factory=lambda: ft.ButtonStyle(
                shape=ft.RoundedRectangleBorder(radius=20)
            )
        )
        icon: ft.IconDataOrControl = ft.Icons.HEADPHONES

    @ft.control
    class MyButton3(ft.Button):
        def init(self):
            self.expand = 1
            self.bgcolor = ft.Colors.RED_ACCENT
            self.style = ft.ButtonStyle(shape=ft.RoundedRectangleBorder(radius=30))
            self.icon = ft.Icons.HEADPHONES

    page.add(
        ft.Row([MyButton(content="1")]),
        ft.Row([MyButton2(content="2")]),
        ft.Row([MyButton3(content="3")]),
    )


ft.run(main)

Rules:

1. You should define either @dataclass or @ft.control decorator on the inherited class - both methods works the same.
2. A field, to be a class field, must have a type annotation, so expand: int = 1 will override inherited property, but expand = 1 won't. Not sure which type to use? Just Any will work, for example expand: Any = 1.
3. Use literal default value for simple data types, such as int, bool, str and field(default_factory=lambda: <new_value>) for immutable types such as class, list, dict.
4. You can set property values in init() method, but you won't be able to override if write MyButton3(expand=False).

Summary by Sourcery

Support correct encoding of dataclass-based controls with overridden default values and document custom control default configuration through examples.

New Features:

• Add support for emitting overridden default values when encoding dataclass-based controls that inherit from other controls.
• Provide an example app demonstrating different ways to define custom controls and their default property values using dataclasses and control decorators.

Bug Fixes:

• Fix control encoding so that defaults defined on base dataclass controls are respected while still emitting overridden defaults from subclasses.

Tests:

• Add a regression test ensuring that encoded output includes subclass-overridden defaults for dataclass control fields.

[sourcery-ai]

We've reviewed this pull request using the Sourcery rules engine

[cloudflare-workers-and-pages]

Deploying flet-docs with    Cloudflare Pages

Latest commit:	464cafc
Status:	✅  Deploy successful!
Preview URL:	https://30a8a486.flet-docs.pages.dev
Branch Preview URL:	https://override-control-props-fix.flet-docs.pages.dev

View logs

[ndonkoHenri]

Nice feature!

Can you please update docs too: https://docs.flet.dev/cookbook/custom-controls/ ?

[ndonkoHenri]

nit;

Me going through this function: 😵‍💫
Little comments here and there will be awesome.

[FeodorFitsner]

😈