guiclass throws type error with Optional argument set to None

[neili02]

Describe the bug

None not accepted as Optional type but should be.

To Reproduce
Steps to reproduce the behavior:

from magicgui.experimental import guiclass
from typing import Optional

@guiclass
class Person:
name:str
age: Optional[int] = None

person = Person('Jane')
person.gui.show()

Expected behavior

Works fine as a normal dataclass since Optional type is Union of None. magicgui tries to cast values to float only
Same error with Union[ int, None]

Screenshots

TypeError Traceback (most recent call last)

File ~\anaconda3\envs\magicgu\lib\site-packages\magicgui\schema_guiclass.py:249, in GuiBuilder.get(self, instance, owner)
247 if instance is None:
248 return self
--> 249 wdg = build_widget(instance)
251 # look for @button-decorated methods
252 # TODO: move inside build_widget?
253 for k, v in vars(owner).items():

File ~\anaconda3\envs\magicgu\lib\site-packages\magicgui\schema_ui_field.py:856, in build_widget(cls_or_instance)
854 values = None if isinstance(cls_or_instance, type) else _get_values(cls_or_instance)
855 fields = get_ui_fields(cls_or_instance)
--> 856 return _uifields_to_container(fields, values=values)

File ~\anaconda3\envs\magicgu\lib\site-packages\magicgui\schema_ui_field.py:817, in _uifields_to_container(ui_fields, values, container_kwargs)
812 container = widgets.Container(
813 widgets=[field.create_widget() for field in ui_fields],
814 **(container_kwargs or {}),
815 )
816 if values is not None:
--> 817 container.update(values)
818 return container

File ~\anaconda3\envs\magicgu\lib\site-packages\magicgui\widgets\bases_container_widget.py:445, in ContainerWidget.update(self, mapping, **kwargs)
443 for key, value in chain(items, kwargs.items()):
444 if isinstance(wdg := self._list.get_by_name(key), BaseValueWidget):
--> 445 wdg.value = value
446 self.changed.emit(self)

File ~\anaconda3\envs\magicgu\lib\site-packages\magicgui\widgets\bases_value_widget.py:103, in BaseValueWidget.value(self, value)
101 @value.setter
102 def value(self, value: T) -> None:
--> 103 return self.set_value(value)

File ~\anaconda3\envs\magicgu\lib\site-packages\magicgui\widgets\bases_ranged_widget.py:124, in RangedWidget.set_value(self, value)
122 """Set widget value, will raise Value error if not within min/max."""
123 val: tuple[float, ...] = value if isinstance(value, tuple) else (value,)
--> 124 if any(float(v) < self.min or float(v) > self.max for v in val):
125 raise ValueError(
126 f"value {value} is outside of the allowed range: "
127 f"({self.min}, {self.max})"
128 )
129 super().set_value(value)

File ~\anaconda3\envs\magicgu\lib\site-packages\magicgui\widgets\bases_ranged_widget.py:124, in (.0)
122 """Set widget value, will raise Value error if not within min/max."""
123 val: tuple[float, ...] = value if isinstance(value, tuple) else (value,)
--> 124 if any(float(v) < self.min or float(v) > self.max for v in val):
125 raise ValueError(
126 f"value {value} is outside of the allowed range: "
127 f"({self.min}, {self.max})"
128 )
129 super().set_value(value)

TypeError: float() argument must be a string or a number, not 'NoneType'

Environment (please complete the following information):

• OS: [Windows]
• backend: [pyqt 5.15.2]
• magicgui version [0.10.1]

[tlambert03]

hi @neili02, this is essentially the same as #145

basically, it will require some magic, or at the very least the concept of a nullable widget (for every type) that can fallback gracefully to None. And there hasn't been a good PR/proposal for how to deal with this in a general way. Sorry we don't have a better ready-to-go widget solution for optional types