Inserting interior subgraphs fails

[jl-wynen]

Given a base graph with a hole, I would like to insert a component subgraph to fill that hole. Eor example, below, component fits into the hole between B and N in the base graph.

flowchart LR
    subgraph component
        direction LR
        nB[B] -->|fn| nN[N]
    end
    subgraph base
        direction LR
        A -->|f1| B
        B ~~~ N
        N -->|f2| C
    end

Loading

I would like to use base[N] = component to construct a complete graph. But Sciline complains with

ValueError: Node inputs differ for node '__main__.B':
  {__main__.A: {'key': __main__.A}}
  {}

The reason is that in base, there is a dependency of B on A. But in component, B does not have a dependency.

Is it possible to support this use case? Here, this should be fine because component does not have a way to provide B, i.e., B is missing. So basically, can we allow merging nodes where in one graph, the node is missing?

For more context: I encountered this in the monitor normalisation in ESSdiffraction where I want to insert either one of the monitor normalisation providers or the proton charge normalisation provider. I can implement this particular case by inserting a provider into base instead of a subgraph. But in general, it would be useful to insert subgraphs when a single provider is not enough.

[SimonHeybrock]

Are you saying that B has neither a value nor a provider? I think this may indeed be a special "unintialized" case that should be accepted by Cyclebane?

[jl-wynen]

Are you saying that B has neither a value nor a provider?

Yes. component only contains fn.

[SimonHeybrock]

I think the key question to figure out is how to distinguish this from true graph-structure mismatches. See https://github.com/scipp/cyclebane/blob/ee09d242d4bfd14471cfffa067d0101e620de00d/tests/graph_test.py#L605-L616.