Connected components for immutable digraphs does not work

[tscrim]

sage: G = DiGraph([[1,2]])
sage: G.connected_components()
[[1, 2]]
sage: G.copy(immutable=True).connected_components()
...
AttributeError: 'NoneType' object has no attribute 'out_neighbors'

CC: @nathanncohen

Component: graph theory

Author: Nathann Cohen

Branch/Commit: 7635a24

Reviewer: Travis Scrimshaw

Issue created by migration from https://trac.sagemath.org/ticket/16019

[nathanncohen]

Commit: 7635a24

[nathanncohen]

Branch: u/ncohen/16019

[nathanncohen]

Author: Nathann Cohen

[nathanncohen]

comment:3

sigh

That's the best I can do, and I am not proud of it ^^;

Nathann

P.S. : You are the one at fault, actually. Who the hell computes connected components on digraphs ? It does not make any sense ! :-P

---

New commits:

7635a24

trac #16019: Broken Connected Components for immutable digraphs

[tscrim]

comment:4

LGTM. Thanks Nathann.

It came up with Dynkin diagrams (which slightly abuses DiGraph) and connected components correspond to irreducible types.

[tscrim]

Reviewer: Travis Scrimshaw

[vbraun]

Changed branch from u/ncohen/16019 to 7635a24