`OptionList` not fully updating on options being cleared (since v2.0.0)

[davep]

Given this code:

from textual.app import App, ComposeResult
from textual.widgets import OptionList

class BadScrollBarApp(App[None]):

    BINDINGS = [
        ("space", "nuke")
    ]

    def compose(self) -> ComposeResult:
        yield OptionList(*[f"Option {n}" for n in range(500)])

    def action_nuke(self) -> None:
        self.query_one(OptionList).clear_options()

if __name__ == "__main__":
    BadScrollBarApp().run()

With textual v3.x, on startup, it looks as you'd expect:

but then after pressing space it looks like this:

note how the widget itself is still the full height of the screen despite OptionList being height: auto; and also note how the scrollbar still seems to think there is the full range of options.

Going back through Textual releases, the last time I see the expected behaviour is with Textual v1.0.0; where after pressing space we see this:

Installing Textual v2.0.0 introduces the problem.

[davep]

Testing further, this seems to be an issue with (m)any changes to an OptionList that change the vertical height of the contents. For example, taking this variation on the above example code:

from textual.app import App, ComposeResult
from textual.widgets import OptionList

class BadScrollBarApp(App[None]):

    BINDINGS = [
        ("space", "nuke")
    ]

    def compose(self) -> ComposeResult:
        yield OptionList(*[f"Option {n}" for n in range(500)])

    def action_nuke(self) -> None:
        for _ in range(50):
            self.query_one(OptionList).remove_option_at_index(0)

if __name__ == "__main__":
    BadScrollBarApp().run()

if you slap space a few times (yes, it will eventually crash, "this ain't that kind of movie kid") you'll see the options get remove but the scrollbar never reflects the change in vertical height of the options.

Again, testing the same code with textual v1.0.0, OptionList works as expected.

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