Describe the bug

graph_from_literal() does not preserve the edge order, which makes it inconvenient (and confusing) to set edge attributes on a graph right after creation. There is an instance of this going wrong here: https://stackoverflow.com/q/76345800/695132

graph <- graph.formula(
  A -+ B,
  B -+ C,
  C -+ D,
  D -+ E,
  A -+ D,
  B -+ D,
  B -+ E
)

E(graph)$weight <- c(3, 2, 4, 5, 5, 1, 4)

The user assumed that A -> B will have weight 3, B->C weight 2, and so on. But this is not the case.

To reproduce

Notice that the edge order of the graph does not correspond to the edge order used in the creation formula.

> g <- graph_from_literal(A -+ B, B -+ C, C -+ D, D -+ E, A -+ D, B -+ D, B -+ E)
> E(g)
+ 7/7 edges from e733585 (vertex names):
[1] A->B A->D B->C B->D B->E C->D D->E

Both the Python and Mathematica interfaces preserve the edge order. It was surprising to me to discover that the R interface does not.

Version information

1.4.3 and igraph_1.4.99.9014