fix(transition-status): improve transition status called with no transitions

ophyd_devices/utils/psi_device_base_utils.py

@@ -6,12 +6,11 @@ import threading
 import traceback
 import uuid
 from enum import Enum
-from typing import TYPE_CHECKING, Callable, Literal
+from typing import TYPE_CHECKING, Callable, Literal, Union
 
 from bec_lib.file_utils import get_full_path
 from bec_lib.logger import bec_logger
 from bec_lib.utils.import_utils import lazy_import_from
-from ophyd import Device, Signal
 from ophyd.status import DeviceStatus as _DeviceStatus
 from ophyd.status import MoveStatus as _MoveStatus
 from ophyd.status import Status as _Status
@@ -19,6 +18,7 @@ from ophyd.status import StatusBase as _StatusBase
 
 if TYPE_CHECKING:  # pragma: no cover
     from bec_lib.messages import ScanStatusMessage
+    from ophyd import Device, Signal
 else:
     # TODO: put back normal import when Pydantic gets faster
     ScanStatusMessage = lazy_import_from("bec_lib.messages", ("ScanStatusMessage",))
@@ -53,7 +53,13 @@ class StatusBase(_StatusBase):
     """Base class for all status objects."""
 
     def __init__(
-        self, obj: Device | None = None, *, timeout=None, settle_time=0, done=None, success=None
+        self,
+        obj: Union["Device", None] = None,
+        *,
+        timeout=None,
+        settle_time=0,
+        done=None,
+        success=None,
     ):
         self.obj = obj
         super().__init__(timeout=timeout, settle_time=settle_time, done=done, success=success)
@@ -129,7 +135,7 @@ class Status(_Status):
 
 
 class DeviceStatus(_DeviceStatus):
-    """Thin wrapper around DeviceStatus to add __and__ operator and add stop on failure option, defaults to False"""
+    """Thin wrapper around DeviceStatus to add __and__ operator."""
 
     def __and__(self, other):
         """Returns a new 'composite' status object, AndStatus"""
@@ -149,7 +155,7 @@ class SubscriptionStatus(StatusBase):
 
     def __init__(
         self,
-        obj: Device | Signal,
+        obj: Union["Device", "Signal"],
         callback: Callable,
         event_type=None,
         timeout=None,
@@ -328,6 +334,8 @@ class TransitionStatus(SubscriptionStatus):
     ):
         self._signal = signal
         self._transitions = tuple(transitions)
+        if not transitions:
+            raise ValueError("Transitions {transitions}must contain at least one value")
         self._index = 0
         self._strict = strict
         self._failure_states = failure_states if failure_states else []
@@ -397,7 +405,13 @@ class TaskStatus(StatusBase):
     """Thin wrapper around StatusBase to add information about tasks"""
 
     def __init__(
-        self, obj: Device | Signal, *, timeout=None, settle_time=0, done=None, success=None
+        self,
+        obj: Union["Device", "Signal"],
+        *,
+        timeout=None,
+        settle_time=0,
+        done=None,
+        success=None,
     ):
         super().__init__(
             obj=obj, timeout=timeout, settle_time=settle_time, done=done, success=success
@@ -423,7 +437,7 @@ class TaskStatus(StatusBase):
 class TaskHandler:
     """Handler to manage asynchronous tasks"""
 
-    def __init__(self, parent: Device):
+    def __init__(self, parent: "Device"):
         """Initialize the handler"""
         self._tasks = {}
         self._parent = parent