fix(option list): fix crash on empty option list with auto width

CHANGELOG.md

@@ -40,6 +40,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - Fixed special case with calculating the height of a container where all children have dynamic heights https://github.com/Textualize/textual/pull/5463
 - Fixed scrollbars ignoring background opacity https://github.com/Textualize/textual/issues/5458
 - Fixed `Header` icon showing command palette tooltip when disabled https://github.com/Textualize/textual/pull/5427
+- Fixed crash on empty `OptionList` with auto width https://github.com/Textualize/textual/issues/5489
 
 
 ## [1.0.0] - 2024-12-12

src/textual/widgets/_option_list.py

@@ -391,6 +391,8 @@ def _populate(self) -> None:
 
     def get_content_width(self, container: Size, viewport: Size) -> int:
         """Get maximum width of options."""
+        if not self._options:
+            return 0
         console = self.app.console
         options = console.options
         padding = self.get_component_styles("option-list--option").padding

tests/option_list/test_option_list_create.py

@@ -161,3 +161,21 @@ async def test_options_are_available_soon() -> None:
     option = Option("", id="some_id")
     option_list = OptionList(option)
     assert option_list.get_option("some_id") is option
+
+
+async def test_empty_option_list_with_auto_width_doesnt_crash() -> None:
+    """Regression test for https://github.com/Textualize/textual/issues/5489"""
+
+    class EmptyOptionListApp(App):
+        CSS = """
+        OptionList {
+            width: auto;
+        }
+        """
+
+        def compose(self) -> ComposeResult:
+            yield OptionList()
+
+    async with EmptyOptionListApp().run_test() as pilot:
+        # If no exception is raised, this test will pass.
+        option_list = pilot.app.query_one(OptionList)