add_vertex! API

[filchristou]

Some discussions (JuliaGraphs/Graphs.jl#122, JuliaGraphs/Graphs.jl#146, JuliaGraphs/Graphs.jl#165) argue that add_vertex! should return the index of the newly added vertex. Currently, the compromise is that add_vertex! returns Bool.

Would you consider entering a transient phase and support both ?

For example, this would mean appropriately modifying the following line:

MetaGraphsNext.jl/src/graphs.jl

Line 117 in 71cf31d

if added

A valid alternative would be to check nv(meta_graph.graph) before and after the add_vertex! operation.

Motivation

As mentioned in #40 and QuantumBFS/Multigraphs.jl#17 I would like to generalize the use cases for MetaGraphsNext and more specifically have it work with Multigraphs.
Multigraphs.jl's add_vertex! already return an index.

[bramtayl]

I'm indifferent here. If I had designed it, I'd have it return nothing, because users can also just use nv to find the new number of vertices, and error if the vertex wasn't added. But if others find it useful, sure, we can return the new index.

[filchristou]

MetaGraphsNext.jl is actually a wrapper, so I wouldn't try to impose a new style. add_vertex!(mg::MetaGraphsNext.MetaGraph) should return whatever add_vertex!(mg.graph) returns. The best we can do, is at least handle the API internally in a neutral fashion. Instead of doing the check if add_vertex!(mg.graph) do the check

nvnum = nv(mg.graph)
add_vertex!(mg.graph)
if nv(mg.graph) != nvnum ...

If you agree with this changes, let me know and I can start working on a PR to substitute such checks.

[bramtayl]

Sure that sounds good thanks!

[gdalle]

If you agree with this changes, let me know and I can start working on a PR to substitute such checks.

I also agree with this :)

[filchristou]

can you please assign this issue on me, so that I don't forget this ?

[gdalle]

Fixed by #47