Update choices setter for categorical widget to ensure _default_choices are updated when a callable choices is passed

src/magicgui/widgets/bases/_categorical_widget.py

@@ -137,7 +137,9 @@ def choices(self, choices: ChoicesType) -> None:
             str_func = choices["key"]
         elif not isinstance(choices, EnumMeta) and callable(choices):
             _choices = choices(self)
-
+            # ensure that when setting choices with a callable,
+            # the default choices are also updated with that callable
+            self._default_choices = choices
         else:
             _choices = choices
 

tests/test_widgets.py

@@ -721,6 +721,23 @@ def test_categorical_change_choices(Cls):
     assert wdg.choices == c
 
 
+@pytest.mark.parametrize("Cls", [widgets.ComboBox, widgets.RadioButtons])
+def test_categorical_change_choices_callable(Cls):
+    first_choices = ("a", "b")
+
+    def get_choices(wdg):
+        return ("c", "d")
+
+    wdg = Cls(choices=first_choices)
+    assert wdg.choices == first_choices
+    assert wdg._default_choices == first_choices
+
+    wdg.choices = get_choices
+
+    assert wdg.choices == ("c", "d")
+    assert wdg._default_choices == get_choices
+
+
 @pytest.mark.skipif(use_app().backend_name != "qt", reason="only on qt")
 def test_radiobutton_reset_choices():
     """Test that reset_choices doesn't change the number of buttons."""