get_option in SelectionList not working about textual HOT 3 OPEN

This would seem to be down to the internals of the underlying OptionList not being fully-built until the widget itself is fully displayed (which it won't be in on_mount). Compare the above with:

from textual.app import App
from textual.widgets import SelectionList
from textual.widgets.selection_list import Selection

class QuickApp(App):

    BINDINGS = [
        ("f", "find"),
    ]

    def compose(self):
        yield SelectionList(
            Selection("a", 1, id="a")
        )

    def action_find(self):
        self.notify(f"{self.query_one(SelectionList).get_option('a')}")

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

Once the app is up and running, press f.

(aside: IIRC this isn't the only widget in Textual where this can be a gotcha).

from textual.

This should work. The Mount message is a guarantee that child widgets are ready to be used. We don't want to deviate from that.

from textual.

Given Dave's clarification, I'm not sure we can do a lot here...
Maybe in get_option raise a different exception saying it's too early to query options by ID?

from textual.