Add defaults values to context dependent destinations

routemaster/config/loader.py

@@ -293,6 +293,7 @@ def _load_context_next_states(
             )
             for idx, yaml_option in enumerate(yaml_next_states['destinations'])
         ],
+        default=yaml_next_states['default'],
     )
 
 

routemaster/config/model.py

@@ -78,18 +78,19 @@ class ContextNextStates(NamedTuple):
     """Defined a choice based on a path in the given `label_context`."""
     path: str
     destinations: Iterable[ContextNextStatesOption]
+    default: str  # noqa: E704 misidentified "multiple statements on one line"
 
     def next_state_for_label(self, label_context: 'Context') -> str:
         """Returns next state based on context value at `self.path`."""
         val = label_context.lookup(self.path.split('.'))
         for destination in self.destinations:
             if destination.value == val:
                 return destination.state
-        raise RuntimeError("Handle this gracefully.")
+        return self.default
 
     def all_destinations(self) -> Iterable[str]:
         """Returns all possible destination states."""
-        return [x.state for x in self.destinations]
+        return [x.state for x in self.destinations] + [self.default]
 
 
 class NoNextStates(NamedTuple):

routemaster/config/schema.yaml

@@ -110,6 +110,8 @@ properties:
                           type:
                             const: 'metadata'
                           path: *dotted_path_definition
+                          default:
+                            type: string
                           destinations:
                             type: array
                             minItems: 1

routemaster/config/tests/test_loading.py

@@ -115,7 +115,8 @@ def test_realistic_config():
                                     state='stage3',
                                     value='2',
                                 ),
-                            ]
+                            ],
+                            default='end',
                         ),
                         exit_condition=ExitConditionProgram(
                             'foo.bar is defined',
@@ -271,7 +272,8 @@ def test_environment_variables_override_config_file_for_database_config():
                                     state='stage3',
                                     value='2',
                                 ),
-                            ]
+                            ],
+                            default='end',
                         ),
                         exit_condition=ExitConditionProgram(
                             'foo.bar is defined',

routemaster/config/tests/test_next_states.py

@@ -29,24 +29,25 @@ def test_context_next_states(make_context):
             ContextNextStatesOption(state='1', value=True),
             ContextNextStatesOption(state='2', value=False),
         ],
+        default='3',
     )
 
     context = make_context(label='label1', metadata={'foo': True})
 
-    assert next_states.all_destinations() == ['1', '2']
+    assert next_states.all_destinations() == ['1', '2', '3']
     assert next_states.next_state_for_label(context) == '1'
 
 
-def test_context_next_states_raises_for_no_valid_state(make_context):
+def test_context_next_states_returns_default_if_no_match(make_context):
     next_states = ContextNextStates(
         path='metadata.foo',
         destinations=[
             ContextNextStatesOption(state='1', value=True),
             ContextNextStatesOption(state='2', value=False),
         ],
+        default='3',
     )
 
     context = make_context(label='label1', metadata={'foo': 'bar'})
 
-    with pytest.raises(RuntimeError):
-        next_states.next_state_for_label(context)
+    assert next_states.next_state_for_label(context) == '3'

routemaster/conftest.py

@@ -70,10 +70,6 @@
                 next_states=ContextNextStates(
                     path='feeds.tests.should_do_alternate_action',
                     destinations=[
-                        ContextNextStatesOption(
-                            state='perform_action',
-                            value=None,
-                        ),
                         ContextNextStatesOption(
                             state='perform_action',
                             value=False,
@@ -83,6 +79,7 @@
                             value=True,
                         ),
                     ],
+                    default='perform_action',
                 ),
                 exit_condition=ExitConditionProgram(
                     'metadata.should_progress = true',
@@ -99,10 +96,6 @@
                 next_states=ContextNextStates(
                     path='feeds.tests.should_loop',
                     destinations=[
-                        ContextNextStatesOption(
-                            state='end',
-                            value=None,
-                        ),
                         ContextNextStatesOption(
                             state='end',
                             value=False,
@@ -112,6 +105,7 @@
                             value=True,
                         ),
                     ],
+                    default='end',
                 ),
             ),
             Gate(

routemaster/tests/test_validation.py

@@ -109,7 +109,8 @@ def test_nonexistent_node_destination_invalid(app_config):
                             state='end',
                             value='2',
                         ),
-                    ]
+                    ],
+                    default='end',
                 ),
                 exit_condition=ExitConditionProgram('false'),
             ),

test_data/realistic.yaml

@@ -26,6 +26,7 @@ state_machines:
         next:
           type: context
           path: foo.bar
+          default: end
           destinations:
             - state: stage3
               value: '1'