remove_state can deal with nested states, incoming transitions, compo…

…und's initial value and history's memory value.

CHANGELOG.rst

@@ -24,19 +24,18 @@ The YAML format of a statechart also changed, look carefully at the changelog an
 - (Changed) Statechart: ``register_state`` is now ``add_state``.
 - (Changed) Statechart: ``register_transition`` is now ``add_transition``.
 - (Changed) Statechart: now defines a root state.
+- (Changed) Statechart: checks done in ``validate``.
 - (Changed) Transition: ``.event`` is a string instead of an ``Event`` instance.
 - (Changed) Transition: attributes ``from_state`` and ``to_state`` are renamed into ``source`` and ``target``.
 - (Changed) Event: ``__eq__`` takes ``data`` attribute into account.
 - (Changed) Event: ``event.foo`` raises an ``AttributeError`` instead of a ``KeyError`` if ``foo`` is not defined.
 - (Changed) State: ``StateMixin.name`` is now read-only (use ``Statechart.rename_state``).
 - (Changed) State: split ``HistoryState`` into a mixin ``HistoryStateMixin`` and two concrete subclasses,
   namely ``ShallowHistoryState`` and ``DeepHistoryState``.
-- (Changed) IO: Complete rewrite of ``io.import_from_yaml`` to load states before transitions. This function does not anymore
-  accept a ``validate_statechart`` parameter. Its ``validate_schema`` parameter is now ``not ignore_schema``.
+- (Changed) IO: Complete rewrite of ``io.import_from_yaml`` to load states before transitions. Parameter names have changed.
 - (Changed) Module: adapt module hierarchy (no visible API change).
 - (Changed) Module: expose module content through ``__all__``.
 - (Removed) IO: ``io.export_to_yaml``.
-- (Removed) Statechart: ``validate`` method.
 - (Removed) Transition: ``transitions`` attribute on ``TransitionStateMixin``, use ``Statechart.transitions_for`` instead.
 - (Removed) State: ``CompositeStateMixin.children``, use ``Statechart.children_for`` instead.
 

sismic/model.py

@@ -372,39 +372,47 @@ def add_state(self, state: StateMixin, parent):
 
     def remove_state(self, name: str):
         """
-        Remove given state. The state can only be removed if it has no more children and no more
-        incoming transitions. Outgoing transitions are removed in the process.
+        Remove given state.
+
+        The transitions that involve this state will be removed too.
+        If the state is the target of an *initial* or *memory* property, their value will be set to None.
+        If the state has children, they will be removed too.
 
         :param name: name of a state
         :raise StatechartError:
         """
         state = self.state_for(name)
 
-        if len(self.children_for(name)) == 0:
-            # Transitions?
-            incoming_transitions = self.transitions_to(name)
-            all_internal = all([t.internal for t in incoming_transitions])
-
-            if not all_internal:
-                raise StatechartError('Cannot remove {} while it has incoming transitions'.format(state))
+        # Remove children
+        for child in self.children_for(state.name):
+            self.remove_state(child)
 
-            # Remove incoming transitions (they are internal ones!)
-            for transition in incoming_transitions:
+        # Remove transitions
+        for transition in list(self.transitions):  # Make a copy!
+            if transition.source == state.name or transition.target == state.name:
                 self.remove_transition(transition)
 
-            # Remove outgoing transitions
-            for transition in self.transitions_from(name):
-                self.remove_transition(transition)
+        # Remove compoundstate's initial and historystate's memory
+        for other_name, other_state in self._states.items():
+            if isinstance(other_state, CompoundState):
+                other_state.initial = None
+            elif isinstance(other_state, HistoryStateMixin):
+                other_state.memory = None
 
-            # Unregister state
-            try:
-                self._children.pop(name)
-            except KeyError:
-                pass
+        # Remove state
+        try:
+            self._children.pop(name)
+        except KeyError:
+            pass
+        try:
             self._parent.pop(name)
-            self._states.pop(name)
-        else:
-            raise StatechartError('Cannot remove {} while it has nested states'.format(state))
+        except KeyError:
+            pass
+
+        self._states.pop(name)
+
+        if self.root == state.name:
+            self._root = None
 
     def rename_state(self, old_name: str, new_name: str):
         """

tests/test_model.py

@@ -280,9 +280,10 @@ def test_remove_unexisting_state(self):
         with self.assertRaises(exceptions.StatechartError):
             self.sc.remove_state('unknown')
 
-    def test_remove_inappropriate_state(self):
-        with self.assertRaises(exceptions.StatechartError):
-            self.sc.remove_state('s2')
+    def test_remove_root_state(self):
+        self.sc.remove_state('root')
+        self.assertEqual(len(self.sc.transitions), 0)
+        self.assertEqual(len(self.sc.states), 0)
 
     def test_remove_appropriate_state(self):
         self.sc.remove_state('active')