De-abstract Savable by making it a protocol

docs/source/nitpick-exceptions

@@ -18,7 +18,7 @@ py:class kiwipy.communications.Communicator
 
 # unavailable forward references
 py:class plumpy.process_states.Command
-py:class plumpy.process_states.State
+py:class plumpy.state_machine.State
 py:class plumpy.base.state_machine.State
 py:class State
 py:class Process

docs/source/tutorial.ipynb

@@ -281,7 +281,7 @@
     "    def continue_fn(self):\n",
     "        print('continuing')\n",
     "        # message is stored in the process status\n",
-    "        return plumpy.Kill('I was killed')\n",
+    "        return plumpy.Kill(plumpy.KillMessage.build('I was killed'))\n",
     "\n",
     "\n",
     "process = ContinueProcess()\n",
@@ -1118,7 +1118,7 @@
     "\n",
     "process = SimpleProcess(communicator=communicator)\n",
     "\n",
-    "pprint(communicator.rpc_send(str(process.pid), plumpy.STATUS_MSG).result())"
+    "pprint(communicator.rpc_send(str(process.pid), plumpy.StatusMessage.build()).result())"
    ]
   },
   {

src/plumpy/__init__.py

@@ -9,7 +9,6 @@
 from .exceptions import *
 from .futures import *
 from .loaders import *
-from .mixins import *
 from .persistence import *
 from .ports import *
 from .process_comms import *
@@ -25,7 +24,6 @@
     + processes.__all__
     + utils.__all__
     + futures.__all__
-    + mixins.__all__
     + persistence.__all__
     + communications.__all__
     + process_comms.__all__

src/plumpy/base/state_machine.py

@@ -1,14 +1,30 @@
 # -*- coding: utf-8 -*-
 """The state machine for processes"""
 
+from __future__ import annotations
+
 import enum
 import functools
 import inspect
 import logging
 import os
 import sys
 from types import TracebackType
-from typing import Any, Callable, Dict, Hashable, Iterable, List, Optional, Sequence, Set, Type, Union, cast
+from typing import (
+    Any,
+    Callable,
+    ClassVar,
+    Dict,
+    Hashable,
+    Iterable,
+    List,
+    Optional,
+    Protocol,
+    Sequence,
+    Type,
+    Union,
+    runtime_checkable,
+)
 
 from plumpy.futures import Future
 
@@ -18,7 +34,6 @@
 
 _LOGGER = logging.getLogger(__name__)
 
-LABEL_TYPE = Union[None, enum.Enum, str]
 EVENT_CALLBACK_TYPE = Callable[['StateMachine', Hashable, Optional['State']], None]
 
 
@@ -31,7 +46,7 @@ class StateEntryFailed(Exception):  # noqa: N818
     Failed to enter a state, can provide the next state to go to via this exception
     """
 
-    def __init__(self, state: Hashable = None, *args: Any, **kwargs: Any) -> None:
+    def __init__(self, state: State, *args: Any, **kwargs: Any) -> None:
         super().__init__('failed to enter state')
         self.state = state
         self.args = args
@@ -74,12 +89,12 @@ def event(
     if from_states != '*':
         if inspect.isclass(from_states):
             from_states = (from_states,)
-        if not all(issubclass(state, State) for state in from_states):  # type: ignore
+        if not all(isinstance(state, State) for state in from_states):  # type: ignore
             raise TypeError(f'from_states: {from_states}')
     if to_states != '*':
         if inspect.isclass(to_states):
             to_states = (to_states,)
-        if not all(issubclass(state, State) for state in to_states):  # type: ignore
+        if not all(isinstance(state, State) for state in to_states):  # type: ignore
             raise TypeError(f'to_states: {to_states}')
 
     def wrapper(wrapped: Callable[..., Any]) -> Callable[..., Any]:
@@ -113,57 +128,40 @@ def transition(self: Any, *a: Any, **kw: Any) -> Any:
     return wrapper
 
 
-class State:
-    LABEL: LABEL_TYPE = None
-    # A set containing the labels of states that can be entered
-    # from this one
-    ALLOWED: Set[LABEL_TYPE] = set()
+@runtime_checkable
+class State(Protocol):
+    LABEL: ClassVar[Any]
+    ALLOWED: ClassVar[set[Any]]
+    is_terminal: ClassVar[bool]
 
-    @classmethod
-    def is_terminal(cls) -> bool:
-        return not cls.ALLOWED
+    def __init__(self, *args: Any, **kwargs: Any): ...
 
-    def __init__(self, state_machine: 'StateMachine', *args: Any, **kwargs: Any):
-        """
-        :param state_machine: The process this state belongs to
-        """
-        self.state_machine = state_machine
-        self.in_state: bool = False
+    def enter(self) -> None: ...
 
-    def __str__(self) -> str:
-        return str(self.LABEL)
+    def exit(self) -> None: ...
 
-    @property
-    def label(self) -> LABEL_TYPE:
-        """Convenience property to get the state label"""
-        return self.LABEL
 
-    @super_check
-    def enter(self) -> None:
-        """Entering the state"""
+@runtime_checkable
+class Interruptable(Protocol):
+    def interrupt(self, reason: Exception) -> None: ...
 
-    def execute(self) -> Optional['State']:
+
+@runtime_checkable
+class Proceedable(Protocol):
+    def execute(self) -> State | None:
         """
         Execute the state, performing the actions that this state is responsible for.
         :returns: a state to transition to or None if finished.
         """
+        ...
 
-    @super_check
-    def exit(self) -> None:
-        """Exiting the state"""
-        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':
-        return self.state_machine.create_state(state_label, *args, **kwargs)
 
-    def do_enter(self) -> None:
-        call_with_super_check(self.enter)
-        self.in_state = True
+def create_state(st: StateMachine, state_label: Hashable, *args: Any, **kwargs: Any) -> State:
+    if state_label not in st.get_states_map():
+        raise ValueError(f'{state_label} is not a valid state')
 
-    def do_exit(self) -> None:
-        call_with_super_check(self.exit)
-        self.in_state = False
+    state_cls = st.get_states_map()[state_label]
+    return state_cls(*args, **kwargs)
 
 
 class StateEventHook(enum.Enum):
@@ -187,7 +185,7 @@ def __call__(cls, *args: Any, **kwargs: Any) -> 'StateMachine':
         :param kwargs: Any keyword arguments to be passed to the constructor
         :return: An instance of the state machine
         """
-        inst = super().__call__(*args, **kwargs)
+        inst: StateMachine = super().__call__(*args, **kwargs)
         inst.transition_to(inst.create_initial_state())
         call_with_super_check(inst.init)
         return inst
@@ -214,13 +212,13 @@ def get_states(cls) -> Sequence[Type[State]]:
         raise RuntimeError('States not defined')
 
     @classmethod
-    def initial_state_label(cls) -> LABEL_TYPE:
+    def initial_state_label(cls) -> Any:
         cls.__ensure_built()
         assert cls.STATES is not None
         return cls.STATES[0].LABEL
 
     @classmethod
-    def get_state_class(cls, label: LABEL_TYPE) -> Type[State]:
+    def get_state_class(cls, label: Any) -> Type[State]:
         cls.__ensure_built()
         assert cls._STATES_MAP is not None
         return cls._STATES_MAP[label]
@@ -240,7 +238,7 @@ def __ensure_built(cls) -> None:
         # Build the states map
         cls._STATES_MAP = {}
         for state_cls in cls.STATES:
-            assert issubclass(state_cls, State)
+            assert isinstance(state_cls, State)
             label = state_cls.LABEL
             assert label not in cls._STATES_MAP, f"Duplicate label '{label}'"
             cls._STATES_MAP[label] = state_cls
@@ -264,11 +262,17 @@ def init(self) -> None:
     def __str__(self) -> str:
         return f'<{self.__class__.__name__}> ({self.state})'
 
-    def create_initial_state(self) -> State:
-        return self.get_state_class(self.initial_state_label())(self)
+    def create_initial_state(self, *args: Any, **kwargs: Any) -> State:
+        return self.get_state_class(self.initial_state_label())(self, *args, **kwargs)
+
+    @property
+    def state(self) -> State | None:
+        if self._state is None:
+            return None
+        return self._state
 
     @property
-    def state(self) -> Optional[LABEL_TYPE]:
+    def state_label(self) -> Any:
         if self._state is None:
             return None
         return self._state.LABEL
@@ -300,16 +304,24 @@ def _fire_state_event(self, hook: Hashable, state: Optional[State]) -> None:
     def on_terminated(self) -> None:
         """Called when a terminal state is entered"""
 
-    def transition_to(self, new_state: Union[Hashable, State, Type[State]], *args: Any, **kwargs: Any) -> None:
+    def transition_to(self, new_state: State | None, **kwargs: Any) -> None:
+        """Transite to the new state.
+
+        The new target state will be create lazily when the state is not yet instantiated,
+        which will happened for states not in the expect path such as pause and kill.
+        The arguments are passed to the state class to create state instance.
+        (process arg does not need to pass since it will always call with 'self' as process)
+        """
+        print(f'try: {self._state} -> {new_state}')
         assert not self._transitioning, 'Cannot call transition_to when already transitioning state'
 
-        initial_state_label = self._state.LABEL if self._state is not None else None
+        if new_state is None:
+            return None
+
+        initial_state_label = self.state_label
         label = None
         try:
             self._transitioning = True
-
-            # Make sure we have a state instance
-            new_state = self._create_state_instance(new_state, *args, **kwargs)
             label = new_state.LABEL
 
             # If the previous transition failed, do not try to exit it but go straight to next state
@@ -319,13 +331,12 @@ def transition_to(self, new_state: Union[Hashable, State, Type[State]], *args: A
             try:
                 self._enter_next_state(new_state)
             except StateEntryFailed as exception:
-                # Make sure we have a state instance
-                new_state = self._create_state_instance(exception.state, *exception.args, **exception.kwargs)
+                new_state = exception.state
                 label = new_state.LABEL
                 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
@@ -338,7 +349,11 @@ def transition_to(self, new_state: Union[Hashable, State, Type[State]], *args: A
             self._transitioning = False
 
     def transition_failed(
-        self, initial_state: Hashable, final_state: Hashable, exception: Exception, trace: TracebackType
+        self,
+        initial_state: Hashable,
+        final_state: Hashable,
+        exception: Exception,
+        trace: TracebackType,
     ) -> None:
         """Called when a state transitions fails.
 
@@ -354,49 +369,25 @@ def get_debug(self) -> bool:
     def set_debug(self, enabled: bool) -> None:
         self._debug: bool = enabled
 
-    def create_state(self, state_label: Hashable, *args: Any, **kwargs: Any) -> State:
-        try:
-            return self.get_states_map()[state_label](self, *args, **kwargs)
-        except KeyError:
-            raise ValueError(f'{state_label} is not a valid state')
-
     def _exit_current_state(self, next_state: State) -> None:
         """Exit the given state"""
 
         # If we're just being constructed we may not have a state yet to exit,
         # in which case check the new state is the initial state
         if self._state is None:
-            if next_state.label != self.initial_state_label():
+            if next_state.LABEL != self.initial_state_label():
                 raise RuntimeError(f"Cannot enter state '{next_state}' as the initial state")
             return  # Nothing to exit
 
         if next_state.LABEL not in self._state.ALLOWED:
-            raise RuntimeError(f'Cannot transition from {self._state.LABEL} to {next_state.label}')
+            raise RuntimeError(f'Cannot transition from {self._state.LABEL} to {next_state.LABEL}')
         self._fire_state_event(StateEventHook.EXITING_STATE, next_state)
-        self._state.do_exit()
+        self._state.exit()
 
     def _enter_next_state(self, next_state: State) -> None:
         last_state = self._state
         self._fire_state_event(StateEventHook.ENTERING_STATE, next_state)
         # Enter the new state
-        next_state.do_enter()
+        next_state.enter()
         self._state = next_state
         self._fire_state_event(StateEventHook.ENTERED_STATE, last_state)
-
-    def _create_state_instance(self, state: Union[Hashable, State, Type[State]], *args: Any, **kwargs: Any) -> State:
-        if isinstance(state, State):
-            # It's already a state instance
-            return state
-
-        # OK, have to create it
-        state_cls = self._ensure_state_class(state)
-        return state_cls(self, *args, **kwargs)
-
-    def _ensure_state_class(self, state: Union[Hashable, Type[State]]) -> Type[State]:
-        if inspect.isclass(state) and issubclass(state, State):
-            return state
-
-        try:
-            return self.get_states_map()[cast(Hashable, state)]
-        except KeyError:
-            raise ValueError(f'{state} is not a valid state')