Merge pull request #1245 from DominicOram/do_not_stop_ro_signals

Do not stop devices that cannot be stopped on Status failure

Author: DominicOram

ophyd/status.py

@@ -705,7 +705,8 @@ def __init__(self, device, **kwargs):
     def _handle_failure(self):
         super()._handle_failure()
         self.log.debug("Trying to stop %s", repr(self.device))
-        self.device.stop()
+        if hasattr(self.device, "stop"):
+            self.device.stop()
 
     def __str__(self):
         device_name = self.device.name if self.device else "None"

ophyd/tests/test_status.py

@@ -1,9 +1,10 @@
 import time
-from unittest.mock import Mock
+from unittest.mock import MagicMock, Mock
 
 import pytest
 
 from ophyd import Device
+from ophyd.signal import EpicsSignalRO
 from ophyd.status import (
     MoveStatus,
     StableSubscriptionStatus,
@@ -142,6 +143,23 @@ def cb(*args, done=False, **kwargs):
     assert status.done and status.success
 
 
+def test_subscription_status_does_not_try_and_stop_ro_device():
+    # Arbitrary device
+    d = EpicsSignalRO("Tst:Prefix", name="test")
+
+    # Full fake callback signature
+    def cb(*args, **kwargs):
+        pass
+
+    status = SubscriptionStatus(d, cb, event_type=d.SUB_VALUE)
+    status._settled_event.set()
+    status.set_exception(Exception())
+    status.log.exception = MagicMock()
+
+    status._run_callbacks()
+    status.log.exception.assert_not_called()
+
+
 def test_given_stability_time_greater_than_timeout_then_exception_on_initialisation():
     # Arbitrary device
     d = Device("Tst:Prefix", name="test")