Fix the broken mask selection widget.

app/cara.ipynb

@@ -52,4 +52,4 @@
  },
  "nbformat": 4,
  "nbformat_minor": 4
-}
+}

cara/apps.py

@@ -214,8 +214,7 @@ class WidgetView:
         mask_choice = widgets.Select(options=list(models.Mask.types.keys()), value=name)
 
         def on_mask_change(change):
-            mask = models.Mask.types[change['new']]
-            node.dcs_update_from(mask)
+            node.dcs_select(change['new'])
         mask_choice.observe(on_mask_change, names=['value'])
 
         return widget_group(
@@ -322,6 +321,10 @@ class ExpertApplication:
             state_builder=CARAStateBuilder(),
         )
         self.model_state.dcs_update_from(baseline_model)
+        # For the time-being, we have to initialise the select states. Careful
+        # as values might not correspond to what the baseline model says.
+        self.model_state.infected.mask.dcs_select('No mask')
+
         self.view = WidgetView(self.model_state)
 
     @property

cara/state.py

@@ -294,6 +294,7 @@ class DataclassStatePredefined(DataclassInstanceState):
             raise ValueError(f'The choice {name} is not valid. Possible options are {", ".join(self._choices)}')
         self._selected = name
         self._instance = self._choices[name]
+        self._fire_observers()
 
     def dcs_instance(self):
         return self._choices[self._selected]
@@ -351,7 +352,7 @@ class DataclassStateNamed(DataclassState):
         if name not in self._states:
             raise ValueError(f'The choice {name} is not valid. Possible options are {", ".join(self._states)}')
         self._selected = name
-        self._selected_state()._fire_observers()
+        self._fire_observers()
 
     def _selected_state(self):
         return self._states[self._selected]

cara/tests/test_state.py

@@ -158,6 +158,11 @@ def test_DCS_predefined():
     s.dcs_update_from(opt1)
     assert s.dcs_instance() == opt2
 
+    observer = Mock()
+    s.dcs_observe(observer)
+    s.dcs_select('option 1')
+    observer.assert_called_once_with()
+
 
 def test_DCS_named():
     opt1 = DCSimpleSubclass('a', 1, 3.14)
@@ -201,7 +206,6 @@ def test_DCS_named():
     s.dcs_select('option 1')
     opt1_observer.reset_mock()
 
-    # ASDA
     with s.dcs_state_transaction():
         s.dcs_select('option 2')
         s.dcs_update_from(opt2)