Make auto_load symmetry with auto_save and state/state_label distinguish

src/plumpy/base/state_machine.py

@@ -266,7 +266,13 @@ 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) -> Any:
+    def state(self) -> State | None:
+        if self._state is None:
+            return None
+        return self._state
+
+    @property
+    def state_label(self) -> Any:
         if self._state is None:
             return None
         return self._state.LABEL
@@ -312,7 +318,7 @@ def transition_to(self, new_state: State | None, **kwargs: Any) -> None:
         if new_state is None:
             return None
 
-        initial_state_label = self._state.LABEL if self._state is not None else None
+        initial_state_label = self.state_label
         label = None
         try:
             self._transitioning = True

src/plumpy/event_helper.py

@@ -45,8 +45,7 @@ def recreate_from(cls, saved_state: SAVED_STATE_TYPE, load_context: Optional[Loa
 
         """
         load_context = ensure_object_loader(load_context, saved_state)
-        obj = cls.__new__(cls)
-        auto_load(obj, saved_state, load_context)
+        obj = auto_load(cls, saved_state, load_context)
         return obj
 
     def save(self, save_context: Optional[LoadSaveContext] = None) -> SAVED_STATE_TYPE:

src/plumpy/persistence.py

@@ -20,6 +20,7 @@
     List,
     Optional,
     Protocol,
+    TypeVar,
     cast,
     runtime_checkable,
 )
@@ -535,6 +536,8 @@ def auto_save(obj: Savable, save_context: Optional[LoadSaveContext] = None) -> S
                 value = value.__name__
             elif isinstance(value, Savable) and not isinstance(value, type):
                 # persist for a savable obj, call `save` method of obj.
+                # the rhs branch is for when value is a Savable class, it is true runtime check
+                # of lhs condition.
                 SaveUtil.set_meta_type(out_state, member, META__TYPE__SAVABLE)
                 value = value.save()
             else:
@@ -544,11 +547,25 @@ def auto_save(obj: Savable, save_context: Optional[LoadSaveContext] = None) -> S
     return out_state
 
 
-def auto_load(obj: SavableWithAutoPersist, saved_state: SAVED_STATE_TYPE, load_context: LoadSaveContext) -> None:
+def load_auto_persist_params(
+    obj: SavableWithAutoPersist, saved_state: SAVED_STATE_TYPE, load_context: LoadSaveContext | None
+) -> None:
     for member in obj._auto_persist:
         setattr(obj, member, _get_value(obj, saved_state, member, load_context))
 
 
+T = TypeVar('T', bound=Savable)
+
+
+def auto_load(cls: type[T], saved_state: SAVED_STATE_TYPE, load_context: LoadSaveContext | None) -> T:
+    obj = cls.__new__(cls)
+
+    if isinstance(obj, SavableWithAutoPersist):
+        load_auto_persist_params(obj, saved_state, load_context)
+
+    return obj
+
+
 def _get_value(
     obj: Any, saved_state: SAVED_STATE_TYPE, name: str, load_context: LoadSaveContext | None
 ) -> MethodType | Savable:

src/plumpy/process_states.py

@@ -22,7 +22,6 @@
 import yaml
 from yaml.loader import Loader
 
-from plumpy.persistence import ensure_object_loader
 from plumpy.process_comms import KillMessage, MessageType
 
 try:
@@ -41,6 +40,7 @@
     auto_load,
     auto_persist,
     auto_save,
+    ensure_object_loader,
 )
 from .utils import SAVED_STATE_TYPE
 
@@ -98,8 +98,8 @@ def recreate_from(cls, saved_state: SAVED_STATE_TYPE, load_context: Optional[Loa
         :return: The recreated instance
 
         """
-        obj = cls.__new__(cls)
-        auto_load(obj, saved_state, load_context)
+        load_context = ensure_object_loader(load_context, saved_state)
+        obj = auto_load(cls, saved_state, load_context)
         return obj
 
     def save(self, save_context: Optional[LoadSaveContext] = None) -> SAVED_STATE_TYPE:
@@ -171,15 +171,15 @@ def recreate_from(cls, saved_state: SAVED_STATE_TYPE, load_context: Optional[Loa
 
         """
         load_context = ensure_object_loader(load_context, saved_state)
-        obj = cls.__new__(cls)
-        auto_load(obj, saved_state, load_context)
+        obj = auto_load(cls, saved_state, load_context)
 
-        obj.state_machine = load_context.process
         try:
             obj.continue_fn = utils.load_function(saved_state[obj.CONTINUE_FN])
         except ValueError:
-            process = load_context.process
-            obj.continue_fn = getattr(process, saved_state[obj.CONTINUE_FN])
+            if load_context is not None:
+                obj.continue_fn = getattr(load_context.proc, saved_state[obj.CONTINUE_FN])
+            else:
+                raise
         return obj
 
 
@@ -235,12 +235,8 @@ def recreate_from(cls, saved_state: SAVED_STATE_TYPE, load_context: Optional[Loa
 
         """
         load_context = ensure_object_loader(load_context, saved_state)
-        obj = cls.__new__(cls)
-
-        auto_load(obj, saved_state, load_context)
-
+        obj = auto_load(cls, saved_state, load_context)
         obj.process = load_context.process
-
         obj.run_fn = getattr(obj.process, saved_state[obj.RUN_FN])
 
         return obj
@@ -306,15 +302,12 @@ def recreate_from(cls, saved_state: SAVED_STATE_TYPE, load_context: Optional[Loa
 
         """
         load_context = ensure_object_loader(load_context, saved_state)
-        obj = cls.__new__(cls)
-        auto_load(obj, saved_state, load_context)
-
+        obj = auto_load(cls, saved_state, load_context)
         obj.process = load_context.process
-
         obj.run_fn = getattr(obj.process, saved_state[obj.RUN_FN])
         if obj.COMMAND in saved_state:
-            # FIXME: typing
             obj._command = persistence.load(saved_state[obj.COMMAND], load_context)  # type: ignore
+
         return obj
 
     def interrupt(self, reason: Any) -> None:
@@ -444,9 +437,7 @@ def recreate_from(cls, saved_state: SAVED_STATE_TYPE, load_context: Optional[Loa
 
         """
         load_context = ensure_object_loader(load_context, saved_state)
-        obj = cls.__new__(cls)
-        auto_load(obj, saved_state, load_context)
-
+        obj = auto_load(cls, saved_state, load_context)
         obj.process = load_context.process
 
         callback_name = saved_state.get(obj.DONE_CALLBACK, None)
@@ -550,8 +541,7 @@ def recreate_from(cls, saved_state: SAVED_STATE_TYPE, load_context: Optional[Loa
 
         """
         load_context = ensure_object_loader(load_context, saved_state)
-        obj = cls.__new__(cls)
-        auto_load(obj, saved_state, load_context)
+        obj = auto_load(cls, saved_state, load_context)
 
         obj.exception = yaml.load(saved_state[obj.EXC_VALUE], Loader=Loader)
         if _HAS_TBLIB:
@@ -610,8 +600,7 @@ def recreate_from(cls, saved_state: SAVED_STATE_TYPE, load_context: Optional[Loa
 
         """
         load_context = ensure_object_loader(load_context, saved_state)
-        obj = cls.__new__(cls)
-        auto_load(obj, saved_state, load_context)
+        obj = auto_load(cls, saved_state, load_context)
         return obj
 
     def save(self, save_context: Optional[LoadSaveContext] = None) -> SAVED_STATE_TYPE:
@@ -659,8 +648,7 @@ def recreate_from(cls, saved_state: SAVED_STATE_TYPE, load_context: Optional[Loa
 
         """
         load_context = ensure_object_loader(load_context, saved_state)
-        obj = cls.__new__(cls)
-        auto_load(obj, saved_state, load_context)
+        obj = auto_load(cls, saved_state, load_context)
         return obj
 
     def save(self, save_context: Optional[LoadSaveContext] = None) -> SAVED_STATE_TYPE: