Support non string labels

lib/inspect.ex

@@ -21,7 +21,7 @@ defimpl Inspect, for: DG do
                 [inspect_node(dg, v), "-->", inspect_node(dg, n)]
 
               {_e, ^v, n, label} ->
-                [inspect_node(dg, v), "--", label, "-->", inspect_node(dg, n)]
+                [inspect_node(dg, v), "--", inspect_term(label), "-->", inspect_node(dg, n)]
             end)
             |> Enum.intersperse([line()])
         end
@@ -49,8 +49,11 @@ defimpl Inspect, for: DG do
   defp label(dg, v, prefix) do
     case :digraph.vertex(dg, v) do
       {^v, []} -> [prefix]
-      {^v, l} -> [prefix, "[", l, "]"]
+      {^v, l} -> [prefix, "[", inspect_term(l), "]"]
     end
     |> concat
   end
+
+  defp inspect_term(term) when is_binary(term), do: term
+  defp inspect_term(term), do: inspect(term)
 end

test/dg_test.exs

@@ -74,6 +74,18 @@ defmodule DG.Test do
                    1--one to two-->2[two]
                """)
     end
+
+    test "fancy labels", %{dg: dg} do
+      DG.add_vertex(dg, 1)
+      DG.add_vertex(dg, 2, :c.pid(0, 42, 42))
+      DG.add_edge(dg, 1, 2, :"one to two")
+
+      assert inspect(dg) ==
+               String.trim("""
+               graph LR
+                   1--:\"one to two\"-->2[#PID<0.42.42>]
+               """)
+    end
   end
 
   describe "collectable" do