The isolated/is_isolated() property does not work as intended

[stur86]

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

Describe the bug

The documentation here suggests that controls designated as isolated should ignore their children when updated. This would be potentially useful when e.g. having components that are expensive to update and you want to schedule those updates manually explicitly.

https://flet.dev/docs/getting-started/custom-controls/#isolated-controls

Unfortunately it seems like this is not how it actually works. Here we see how if the isolated argument was passed, it would skip updating the children:

flet/sdk/python/packages/flet/src/flet/core/control.py

Lines 398 to 407 in f8c7baa

	def build_update_commands(
	self, index, commands, added_controls, removed_controls, isolated: bool = False
	) -> None:
	update_cmd = self._build_command(update=True)
	if len(update_cmd.attrs) > 0:
	update_cmd.name = "set"
	commands.append(update_cmd)
	if isolated:
	return

And here we see how it's never set and thus always defaults to False:

flet/sdk/python/packages/flet/src/flet/core/page.py

Lines 813 to 816 in f8c7baa

	for control in controls:
	control.build_update_commands(
	self._index, commands, added_controls, removed_controls
	)

Also the control itself doesn't really make use of the isolated property:

flet/sdk/python/packages/flet/src/flet/core/control.py

Lines 83 to 84 in f8c7baa

	def is_isolated(self) -> bool:
	return False

It's an easy enough fix but I was wondering whether there was a reason for this. I've currently gone around it in my custom component by overriding build_update_commands, but that's obviously hackish.

Code sample

Code

import flet as ft

class UpdateCounter(ft.Text):

    def __init__(self):
        super().__init__()
        self.counter = 0
        self.value = f"Counter: {self.counter}"
        
    def before_update(self):
        self.counter += 1
        self.value = f"Counter: {self.counter}"
        return super().before_update()
    

class Widget(ft.AlertDialog):
    
    def __init__(self):
        super().__init__()
        self.title = ft.Text("Widget")
        close_btn = ft.IconButton(ft.icons.CLOSE, on_click=lambda e: self.hide())
        self.actions = [close_btn]        
        self.content = UpdateCounter()
    
    def is_isolated(self):
        # This actually does nothing
        return True
        
    def show(self):
        self.open = True
        self.update()
    
    def hide(self):
        self.open = False
        self.update()
        
    def build_update_commands(self, index, commands, added_controls, removed_controls, isolated=False):
        # This achieves the desired effect
        return super().build_update_commands(index, commands, added_controls, removed_controls, isolated=True)

def main(page: ft.Page):
    page.title = "Flet App"
    
    widget = Widget()
    btn = ft.FilledButton(text="Open", on_click=lambda e: widget.show())
    page.add(btn)
    page.add(widget)

if __name__ == "__main__":
    ft.app(target=main)

To reproduce

See the above code sample; try commenting out the override of the build_update_commands and note how the content of the widget keeps updating on each open/close.

Expected behavior

Components on which the .isolated property is set to True, or the .is_isolated() method returns True, should not update their children automatically.

Screenshots / Videos

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Operating System

Linux

Operating system details

Ubuntu 22.04, on WSL2

Flet version

Observed in 0.22.1, persists as of 0.26.0

Regression

I'm not sure / I don't know

Suggestions

Simply change the code in page.py to:

        for control in controls:
            control.build_update_commands(
                self._index, commands, added_controls, removed_controls, isolated=control.is_isolated()
            )

Logs

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Additional details

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