4 files changed, 33 insertions, 7 deletions

diff --git a/src/mailman/app/subscriptions.py b/src/mailman/app/subscriptions.py
index 507f8bf28..375fe159d 100644
--- a/src/mailman/app/subscriptions.py
+++ b/src/mailman/app/subscriptions.py
@@ -93,19 +93,30 @@ class Workflow:
         # Note: only the next step is saved, not the whole stack. Not an issue
         # since there's never more than a single step in the queue anyway.
         # If we want to support more than a single step in the queue AND want
-        # to support state saving/restoring, change this method and
-        # restore_state().
+        # to support state saving/restoring, change this method and the
+        # restore_state() method.
+        if len(self._next) == 0:
+            step = None
+        elif len(self._next) == 1:
+            step = self._next[0]
+        else:
+            raise AssertionError(
+                "Can't save a workflow state with more than one step "
+                "in the queue")
         state_manager.save(
             self.__class__.__name__,
             self._save_key,
-            self._next[0],
+            step,
             json.dumps(data))
 
     def restore_state(self):
         state_manager = getUtility(IWorkflowStateManager)
         state = state_manager.restore(self.__class__.__name__, self._save_key)
         if state is not None:
-            self._next[0] = state.step
+            if not state.step:
+                self._next.clear()
+            else:
+                self._next[0] = state.step
             if state.data is not None:
                 for attr, value in json.loads(state.data).items():
                     setattr(self, attr, value)
diff --git a/src/mailman/app/tests/test_subscriptions.py b/src/mailman/app/tests/test_subscriptions.py
index fde33b91e..05646c929 100644
--- a/src/mailman/app/tests/test_subscriptions.py
+++ b/src/mailman/app/tests/test_subscriptions.py
@@ -100,6 +100,21 @@ class TestSubscriptionWorkflow(unittest.TestCase):
         self.assertEqual(workflow.pre_confirmed, False)
         self.assertEqual(workflow.pre_approved, False)
 
+    def test_save_restore_no_next_step(self):
+        anne = self._user_manager.create_address(self._anne, 'Anne Person')
+        workflow = SubscriptionWorkflow(
+            self._mlist, anne,
+            pre_verified=True, pre_confirmed=False, pre_approved=False)
+        workflow._next.pop()
+        self.assertEqual(len(workflow._next), 0)
+        workflow.save_state()
+        # Now create a new instance and restore
+        workflow = SubscriptionWorkflow(
+            self._mlist, anne,
+            pre_verified=None, pre_confirmed=None, pre_approved=None)
+        workflow.restore_state()
+        self.assertEqual(len(workflow._next), 0)
+
     def test_preverified_address_joins_open_list(self):
         # The mailing list has an open subscription policy, so the subscriber
         # becomes a member with no human intervention.
diff --git a/src/mailman/database/alembic/versions/2bb9b382198_workflow_state_table.py b/src/mailman/database/alembic/versions/2bb9b382198_workflow_state_table.py
index 23b3adebb..e6608b6ce 100644
--- a/src/mailman/database/alembic/versions/2bb9b382198_workflow_state_table.py
+++ b/src/mailman/database/alembic/versions/2bb9b382198_workflow_state_table.py
@@ -18,7 +18,7 @@ def upgrade():
     op.create_table('workflowstate',
         sa.Column('name', sa.Unicode(), nullable=False),
         sa.Column('key', sa.Unicode(), nullable=False),
-        sa.Column('step', sa.Unicode(), nullable=False),
+        sa.Column('step', sa.Unicode(), nullable=True),
         sa.Column('data', sa.Unicode(), nullable=True),
         sa.PrimaryKeyConstraint('name', 'key')
     )
diff --git a/src/mailman/model/workflowstate.py b/src/mailman/model/workflowstate.py
index ee0226d61..229a2240b 100644
--- a/src/mailman/model/workflowstate.py
+++ b/src/mailman/model/workflowstate.py
@@ -40,7 +40,7 @@ class WorkflowState(Model):
 
     name = Column(Unicode, primary_key=True)
     key = Column(Unicode, primary_key=True)
-    step = Column(Unicode, nullable=False)
+    step = Column(Unicode)
     data = Column(Unicode)
 
 
@@ -50,7 +50,7 @@ class WorkflowStateManager:
     """See `IWorkflowStateManager`."""
 
     @dbconnection
-    def save(self, store, name, key, step, data=None):
+    def save(self, store, name, key, step=None, data=None):
         """See `IWorkflowStateManager`."""
         state = store.query(WorkflowState).get((name, key))
         if state is None: