cet-is » art

This might not be a bug but I am not sure how else to file it.

Mu2e has an output module Analyses/src/DataProductDump_module.cc

This module predates the file dumper output module and does similar work; we are keeping it around as an example.

This module is created from an output module template:

namespace mu2e {
  class DataProductDumpDetail;
  typedef art::ProvenanceDumper<DataProductDumpDetail> DataProductDump;
}

class mu2e::DataProductDumpDetail {
  // contents deleted.
};

DEFINE_ART_MODULE(mu2e::DataProductDump);

We jumped from art v1_15_00 to art v1_17_02. In art v1_15_00 the module compiled. In art v1_17_02 we had to add an empty definition of the struct Config in order for the module to compile:

class mu2e::DataProductDumpDetail {
public:
   struct Config {};
   // contents deleted.
};

I think that the reason is that the module template now does checking of its parameter set. I think that this forces the detail class to check it's parameter set. Our detail class does not use any parameters providing a correct Config class is trivial.

This should be better documented. We should also have a discussion among the stakeholders about the desired behaviour in this situation: if a module template uses the parameter set validation do we want to require that the detail class does too? What options are there? In the long run I think that forced validation is good. The question is if we need a different policy for the transition period ( it is also possible that for this very narrow question the transition period is now over ).