Bugfix Select.selection with no value selected

Based on the docs Select.selection should return None if no value is
selected, i.e. the value is Select.Blank. It just raised an assertion
error though. Fixed the issue and added a test

Author: Zaloog

CHANGELOG.md

@@ -12,6 +12,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - Static and Label now accept Content objects, satisfying type checkers https://github.com/Textualize/textual/pull/5618
 - Fixed click selection not being disabled when allow_select was set to false https://github.com/Textualize/textual/issues/5627
 - Fixed crash on clicking line API border https://github.com/Textualize/textual/pull/5641
+- Fixed Select.selection now correctly returns None if Select.BLANK is selected instead of an AssertionError
 
 ### Added
 

src/textual/widgets/_select.py

@@ -477,7 +477,8 @@ def selection(self) -> SelectType | None:
 
         """
         value = self.value
-        assert not isinstance(value, NoSelection)
+        if isinstance(value, NoSelection):
+            return None
         return value
 
     def _setup_variables_for_options(

tests/select/test_blank_and_clear.py

@@ -63,3 +63,13 @@ def compose(self):
         assert not select.is_blank()
         with pytest.raises(InvalidSelectValueError):
             select.clear()
+
+async def test_selection_is_none_with_blank():
+    class SelectApp(App[None]):
+        def compose(self):
+            yield Select(SELECT_OPTIONS)
+
+    app = SelectApp()
+    async with app.run_test():
+        select = app.query_one(Select)
+        assert select.selection is None