Bug with `validate_highlighted` after empty OptionList?

[TomJGooding]

This follows on from discussion #3559 about confusing errors when trying to remove options from a SelectionList.

It looks like parent OptionList widget was designed to always have a highlighted option based on the validation?

textual/src/textual/widgets/_option_list.py

Lines 987 to 992 in e68e6e3

	def validate_highlighted(self, highlighted: int | None) -> int | None:
	"""Validate the `highlighted` property value on access."""
	if not self._options:
	return None
	if highlighted is None or highlighted < 0:
	return 0

But if you start with an empty OptionList and then add options later, the highlighted reactive is still None which suggests this validation must not be called.

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[TomJGooding]

If I'm right that OptionList is designed to always have a highlighted option, this might actually cause issues with the CommandPalette?

[davep]

My recollection is that the intended design is that it retains a highlight once there is a highlight

[TomJGooding]

My memory is a little hazy on this issue but I think this is now fixed, likely as part of #3912. Closing.

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