[subgraph.hpp] add_vertex(u_global, g) on a subgraph does not recursively add to parent subgraphs

[s.hammer@…]

Hello,

One of the invariants of an induced subgraph is:

• If vertex u is in subgraph g, then u must be in g.parent().

This is true if you call add_vertex(g) on a subgraph to create a new vertex. If you however choose to add a already existing global vertex to the subgraph, this addition is not propagated to the parents of this subgraph.

I assume this is a bug and fixed it. The patch is on github: ​https://github.com/j-4/graph/tree/fix-add_vertex-subgraph

I also created a pull request! Thanks, Stefan

PS: Attached is a unit test which fails due to this issue and runs through with the patched version!

[s.hammer@…]

Boost unit test for the issue

[Stefan Hammer <s.hammer@…>]

UPDATE: Boost unit test for the issue

[Stefan Hammer <s.hammer@…>]

UPDATE: Boost unit test for the issue

[Murray Cumming <murrayc@…>]

See ​https://github.com/boostorg/graph/pull/45