clarified source of an error message #1086
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in the put method to the EpicsSignal class, there is a check to be sure that the signal can be written to, i.e. that self.write_access is true. that error message results in an unhelpful traceback in that it provides no information identifying the PV triggering the message. in the case of a deeply nested signal, this error message is unilluminating. this commit adds self.name to the error message.
prjemian
reviewed
Jan 3, 2023
| @@ -2056,7 +2056,7 @@ def put( | |||
| use_complete = self._put_complete | |||
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| if not self.write_access: | |||
| raise ReadOnlyError("No write access to underlying EPICS PV") | |||
| raise ReadOnlyError(f"No write access to underlying EPICS PV : {self.name}") | |||
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Since this is an EPICS signal, can you also add the write_pvname to the message? It's one of the diagnostics our instrument teams want to see in such a message.
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Also, the message would be helped by putting the write PV name first as stated.
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in the put method to the EpicsSignal class, there is a check to be sure that the signal can be written to, i.e. that self.write_access is true. that error message results in an unhelpful traceback in that it provides no information identifying the PV triggering the message. in the case of a deeply nested signal, this error message is unilluminating. this commit adds self.name to the error message.
This is, in my opinion, an example of a common anti-pattern in ophyd. There are many error messages that do a poor job identifying the prima causa of the error, simply resulting in a lengthy traceback that is hard to parse for someone not well versed in ophyd's internals.
In my case, I was, with a lot of poking and prodding, able to identify the source of the error. Had the error message included the name (as in
self.name) of the ophyd object, it would have been a much shorter path to identifying the problem.My solution was to simply append
self.nameto the error message. Not a perfect solution, but it would at least point the human doing the debugging in the right direction.I have a hard time believing this is simply a problem for someone like me, who is writing beamline code without also having a deep understanding of Ophyd. I cannot believe that a context-free error message could be helpful even to Ophyd's main developers.
Were I king of the world (or at least of DSSI), I would call for a full audit of ophyd to find all examples of context-free messages like this one. I would then call for agreement on a convention for making better, more helpful, better contextualized error messages.
All right! Rant is finished. Thanks for humoring me 😁