OptionList duplicate ID detection not working as expected

[davep]

Consider the following code:

from textual.app import App, ComposeResult
from textual.widgets import OptionList, Log, Footer
from textual.widgets.option_list import Option

class OptionListAddBug(App[None]):

    BINDINGS = [
        (str(n), f"add({n})", f"Add {n}") for n in range(10)
    ]

    CSS = """
    OptionList, Log {
        height: 1fr;
        border: round cornflowerblue;
    }
    """

    def compose(self) -> ComposeResult:
        yield OptionList()
        yield Log()
        yield Footer()

    def action_add(self, value: int) -> None:
        try:
            self.query_one(OptionList).add_option(
                Option(f"Added {value} just fine", id=f"id-{value}")
            )
        except Exception as error:
            self.query_one(Log).write_line(f"{error!r}")


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

If you run it and press keys 0-9, you'll find that corresponding options are added to the OptionList.

However, if you start the app afresh, then press (for example) 2 twice, resulting in a logged DuplicateID exception (expected and desired), after than you can't add any more options to the list, and the attempted added option is always reported as having the original duplicate ID:

In the above I pressed 2 twice and then a number of other number keys.

It would appear that OptionList is getting every confused in its id tracking and/or duplicate detection.

[TomJGooding]

I found a quick workaround would be:

        except Exception as error:
            self.query_one(Log).write_line(f"{error!r}")

            self.query_one(OptionList)._contents.pop()

The exception is raised by _refresh_content_tracking which loops through _contents.

textual/src/textual/widgets/_option_list.py

Lines 543 to 546 in 6d79e77

	if content.id in option_ids:
	raise DuplicateID(
	f"The option list already has an option with id '{content.id}'"
	)

[davep]

Yeah, pretty sure the duplicate check needs to go waaaaaaay before anything gets added.

[davep]

Smoking gun.

diff --git a/tests/option_list/test_option_list_create.py b/tests/option_list/test_option_list_create.py
index 7e0bbc49..98130d75 100644
--- a/tests/option_list/test_option_list_create.py
+++ b/tests/option_list/test_option_list_create.py
@@ -119,5 +119,8 @@ async def test_add_later() -> None:
 async def test_create_with_duplicate_id() -> None:
     """Adding an option with a duplicate ID should be an error."""
     async with OptionListApp().run_test() as pilot:
+        option_list = pilot.app.query_one(OptionList)
+        assert option_list.option_count == 5
         with pytest.raises(DuplicateID):
-            pilot.app.query_one(OptionList).add_option(Option("dupe", id="3"))
+            option_list.add_option(Option("dupe", id="3"))
+        assert option_list.option_count == 5```

with that change the tests it fails.

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