cet-is » art

There are now many tests in art that verify the expected behavior for various input-concatenation scenarios. Consider the following scenario, however.

Suppose input files a.root and b.root were created by the same set of processes and therefore have the same products and event shape. To save disk space, a user decides to drop products in b.root so that the unneeded products are no longer present, and only the desired products are persisted to b_trimmed.root. Because a.root and b_trimmed.root still have the same event shape, it is possible for both to serve as inputs:

art -c onlyAnalyze.fcl a.root b_trimmed.root

where no filtering or extra product creation is done. This works fine in current art. However, suppose I want to write all the products to an aggregated output (out.root). In this case, the nonexistent products in b_trimmed.root should be replaced with dummies in out.root. However, the following error is emitted:

---- FatalRootError BEGIN
  Fatal Root Error: @SUB=TBranchElement::Fill
  attempt to fill branch art::TriggerResults_TriggerResults__p2. while addresss is not set
  cet::exception going through module RootOutput/out run: 1 subRun: 0 event: 1
---- FatalRootError END

Interestingly, the error is not triggered if b_trimmed.root precedes a.root in the input-file list. This should be remedied so that the behavior is symmetric wrt. the order of the above-specified inputs.