improve error handling, avoid code-duplication

MagneticField/MagFieldConfig/python/BFieldConfigFlags.py

 # Copyright (C) 2002-2024 CERN for the benefit of the ATLAS collaboration
 
 from AthenaConfiguration.AthConfigFlags import AthConfigFlags
+from AthenaCommon.Logging import logging
 
+msg = logging.getLogger('BFieldConfigFlags')
 
 
 #So far no attempt to auto-config field for MC or online-running
 #
 #The old-style config did auto-config the field for online based on IS
-#(see https://gitlab.cern.ch/atlas/athena/-/blame/1802605a4ab69cab7ee3e53d75f162c7da99a944/Reconstruction/RecExample/RecExOnline/python/OnlineISConfiguration.py#L52)
+#(see https://gitlab.cern.ch/atlas/athena/-/blob/1802605a4ab69cab7ee3e53d75f162c7da99a944/Reconstruction/RecExample/RecExOnline/python/OnlineISConfiguration.py#L52)
 #
 #The old-sytle config tried to auto-config the field based on in-file metadata, falling back to Geometry and Conditions tags. See  
-#(see https://gitlab.cern.ch/atlas/athena/-/blame/1802605a4ab69cab7ee3e53d75f162c7da99a944/Reconstruction/RecExample/RecExConfig/python/AutoConfiguration.py#L181
+#(see https://gitlab.cern.ch/atlas/athena/-/blob/1802605a4ab69cab7ee3e53d75f162c7da99a944/Reconstruction/RecExample/RecExConfig/python/AutoConfiguration.py#L181
 
-def _toroidFieldAutoCfg(prevFlags):
+def _fieldAutoCfg(prevFlags):
     if prevFlags.Input.isMC or prevFlags.Common.isOnline:
-        return True
+        return [True,True]
     
     from CoolConvUtilities.MagFieldUtils import getFieldForRun
     lbs=prevFlags.Input.LumiBlockNumbers
     fieldStat=getFieldForRun(run=prevFlags.Input.RunNumbers[0],lumiblock=0 if len(lbs)==0 else lbs[0],quiet=True)
-    return (fieldStat.toroidCurrent()>1)
+    if fieldStat is None:
+        msg.error("Unable to get field status from DCS, assume both magnets ON")
+        return [True,True]
+    return [fieldStat.solenoidCurrent()>1, fieldStat.toroidCurrent()>1]
 
-def _solenoidFieldAutoCfg(prevFlags):
-    if prevFlags.Input.isMC or prevFlags.Common.isOnline:
-        return True
-
-    from CoolConvUtilities.MagFieldUtils import getFieldForRun
-    lbs=prevFlags.Input.LumiBlockNumbers
-    fieldStat=getFieldForRun(run=prevFlags.Input.RunNumbers[0],lumiblock=0 if len(lbs)==0 else lbs[0],quiet=True)
-    return (fieldStat.solenoidCurrent()>1)
     
                               
 def createBFieldConfigFlags(): 
     bcf=AthConfigFlags()
     # True when solenoid is on
-    bcf.addFlag("BField.solenoidOn", _solenoidFieldAutoCfg)
+    bcf.addFlag("BField.solenoidOn", lambda prevFlags : _fieldAutoCfg(prevFlags)[0])
     # True when barrel toroid is on
-    bcf.addFlag("BField.barrelToroidOn", _toroidFieldAutoCfg)
+    bcf.addFlag("BField.barrelToroidOn", lambda prevFlags : _fieldAutoCfg(prevFlags)[1])
     # True when endcap toroid is on
-    bcf.addFlag("BField.endcapToroidOn", _toroidFieldAutoCfg)
+    bcf.addFlag("BField.endcapToroidOn", lambda prevFlags : _fieldAutoCfg(prevFlags)[1])
     return bcf