Change in behavior of scala-graph 2.0 for multiple edges between same two nodes

[Allan Brighton]

I updated to scala-graph 2.0 and noticed a change when two nodes have multiple directed edges with only different labels. In scala-graph 1.x both edges were shown (when converting to Dot), but in 2.0 only one of the edges is shown. Is this expected behavior?

The models I am using look like this:

```

  // Type of an edge label
  private case class EdgeLabel(labels: List[String], edgeType: EdgeType, missing: Option[MissingType] = None) {
    lazy val label: String = labels.sorted.mkString("\\n")
  }

  // Holds both components of an edge
  private case class ComponentPair(from: String, to: String)

  // Describes an Edge from one component to another
  private case class EdgeModel(components: ComponentPair, label: EdgeLabel)

  // Labeled directed edges
  private case class MyLDiEdge(model: EdgeModel)
      extends AbstractDiEdge(source = model.components.from, target = model.components.to)
  private object MyGraph extends TypedGraphFactory[String, MyLDiEdge]

// ...

    val allEdgeModels: List[EdgeModel] = ...
    val g = MyGraph.from(
      allEdgeModels.map(MyLDiEdge)
    )

    // Convert to dot
    val dot = g.toDot(
      dotRoot = root,
      edgeTransformer = edgeTransformer,
      cNodeTransformer = Some(nodeTransformer)
    )

```

[Allan Brighton]

Here is a small example that demonstrates the problem: There should be two edges from "A" to "B", but only one is shown.

(See attached Test.scala)

[empen...@gmail.com]

Did you also try to mix in MultiEdge? The easiest way to define a multigraph is also described in Core User Guide: Plan Your Graph.

Does this help?

[Allan Brighton]

Yes, that was it (MultiEdge). 

Thanks,

Allan