Move is_terminal as class attribute required

src/plumpy/base/state_machine.py

@@ -133,10 +133,6 @@ class State:
     # from this one
     ALLOWED: Set[LABEL_TYPE] = set()
 
-    @classmethod
-    def is_terminal(cls) -> bool:
-        return not cls.ALLOWED
-
     def __init__(self, state_machine: 'StateMachine', *args: Any, **kwargs: Any):
         """
         :param state_machine: The process this state belongs to
@@ -165,7 +161,7 @@ def execute(self) -> Optional['State']:
     @super_check
     def exit(self) -> None:
         """Exiting the state"""
-        if self.is_terminal():
+        if self.is_terminal:
             raise InvalidStateError(f'Cannot exit a terminal state {self.LABEL}')
 
     def create_state(self, state_label: Hashable, *args: Any, **kwargs: Any) -> 'State':
@@ -352,7 +348,7 @@ def transition_to(self, new_state: State | type[State] | None, **kwargs: Any) ->
                 self._exit_current_state(new_state)
                 self._enter_next_state(new_state)
 
-            if self._state is not None and self._state.is_terminal():
+            if self._state is not None and self._state.is_terminal:
                 call_with_super_check(self.on_terminated)
         except Exception:
             self._transitioning = False

src/plumpy/process_states.py

@@ -152,6 +152,7 @@ class Created(state_machine.State, persistence.Savable):
     ALLOWED = {ProcessState.RUNNING, ProcessState.KILLED, ProcessState.EXCEPTED}
 
     RUN_FN = 'run_fn'
+    is_terminal = False
 
     def __init__(self, process: 'Process', run_fn: Callable[..., Any], *args: Any, **kwargs: Any) -> None:
         super().__init__(process)
@@ -200,6 +201,8 @@ class Running(state_machine.State, persistence.Savable):
     _running: bool = False
     _run_handle = None
 
+    is_terminal = False
+
     def __init__(self, process: 'Process', run_fn: Callable[..., Any], *args: Any, **kwargs: Any) -> None:
         super().__init__(process)
         assert run_fn is not None
@@ -293,6 +296,8 @@ class Waiting(state_machine.State, persistence.Savable):
 
     _interruption = None
 
+    is_terminal = False
+
     def __str__(self) -> str:
         state_info = super().__str__()
         if self.msg is not None:
@@ -379,6 +384,8 @@ class Excepted(state_machine.State, persistence.Savable):
     EXC_VALUE = 'ex_value'
     TRACEBACK = 'traceback'
 
+    is_terminal = True
+
     def __init__(
         self,
         process: 'Process',
@@ -447,6 +454,8 @@ class Finished(state_machine.State, persistence.Savable):
 
     LABEL = ProcessState.FINISHED
 
+    is_terminal = True
+
     def __init__(self, process: 'Process', result: Any, successful: bool) -> None:
         super().__init__(process)
         self.result = result
@@ -477,6 +486,8 @@ class Killed(state_machine.State, persistence.Savable):
 
     LABEL = ProcessState.KILLED
 
+    is_terminal = True
+
     def __init__(self, process: 'Process', msg: Optional[MessageType]):
         """
         :param process: The associated process

src/plumpy/processes.py

@@ -467,7 +467,7 @@ def launch(
 
     def has_terminated(self) -> bool:
         """Return whether the process was terminated."""
-        return self._state.is_terminal()
+        return self._state.is_terminal
 
     def result(self) -> Any:
         """
@@ -540,7 +540,7 @@ def done(self) -> bool:
             Use the `has_terminated` method instead
         """
         warnings.warn('method is deprecated, use `has_terminated` instead', DeprecationWarning)
-        return self._state.is_terminal()
+        return self._state.is_terminal
 
     # endregion
 

tests/base/test_statemachine.py

@@ -20,6 +20,8 @@ class Playing(state_machine.State):
     ALLOWED = {PAUSED, STOPPED}
     TRANSITIONS = {STOP: STOPPED}
 
+    is_terminal = False
+
     def __init__(self, player, track):
         assert track is not None, 'Must provide a track name'
         super().__init__(player)
@@ -54,6 +56,8 @@ class Paused(state_machine.State):
     ALLOWED = {PLAYING, STOPPED}
     TRANSITIONS = {STOP: STOPPED}
 
+    is_terminal = False
+
     def __init__(self, player, playing_state):
         assert isinstance(playing_state, Playing), 'Must provide the playing state to pause'
         super().__init__(player)
@@ -76,6 +80,8 @@ class Stopped(state_machine.State):
     }
     TRANSITIONS = {PLAY: PLAYING}
 
+    is_terminal = False
+
     def __str__(self):
         return '[]'