Multiple input feature problem

Question

[Sl.aleksandr28]

I've encountered a problem using MultipleInputFeatureRequirement. It works with required inputs but not with optional inputs. Is this an expected behaviour and if so why?

All code to reproduce the problem and other information are here - https://github.com/AleksandrSl/cwl-problem-samples/tree/master/multiple_input_feature

[Sl.aleksandr28]

I've found workaround for optional parameters using expressions,

source:
  - input_1
  - input_2
valueFrom: $([self[0], self[1]])

Nevertheless this behaviour looks like a bug