Future igraph will consider the null graph disconnected

[Szabolcs Horvát]

Hello nat team,

I am writing on behalf of the igraph project. R/igraph 1.3.0 is due to be released soon and it includes a change that causes the nat test suite to fail. Specifically, the null graph (graph with zero vertices) is now considered disconnected, for reasons of consistency. The failure is coming from cases like this:

as.seglist.igraph(igraph::graph.empty())

(Note: the new name for graph.empty() has been make_empty_graph() for a while.)

Could you please update nat so that it no longer relies on is_connected(make_empty_graph()) being TRUE? Going forward it will be FALSE. You could simply check if vcount(graph) is zero, and if so, accept the graph.

If you are curious for why this change was made for igraph, some of the discussion is here: igraph/igraph#1539

[Szabolcs Horvát]

I guess this is fixed now, closing.