Remove separator vertices and associated edges from serialized output

The separator vertices are an implementation detail of the serialized
output of the LIR, and are not meaningful to the pipeline viewer.

This commit removes the separator vertices, and reworks the edges to
account for this.

Fixes #11779

logstash-core/lib/logstash/config/lir_serializer.rb

@@ -44,11 +44,11 @@ module LogStash;
     end
     
     def vertices
-      graph.getVertices.map {|v| vertex(v) }
+      graph.getVertices.map {|v| vertex(v) }.compact
     end
     
     def edges
-      graph.getEdges.map {|e| edge(e) }
+      remove_separators_from_edges(graph.getEdges)
     end
     
     def graph
@@ -64,10 +64,10 @@ module LogStash;
                          when :queue
                            queue_vertex(v)
                          when :separator
-                           separator_vertex(v)
+                           nil
                          end
 
-      decorate_vertex(v, hashified_vertex)
+      decorate_vertex(v, hashified_vertex) unless hashified_vertex.nil?
     end
     
     def vertex_type(v)
@@ -114,6 +114,24 @@ module LogStash;
       {}
     end
 
+    # For separators, create new edges going between the incoming and all of the outgoing edges, and remove
+    # the separator vertices from the serialized output.
+    def remove_separators_from_edges(edges)
+      edges_with_separators_removed = []
+      edges.each do |e|
+        if vertex_type(e.to) == :separator
+          e.to.getOutgoingEdges.each do |outgoing|
+            edges_with_separators_removed << edge(org.logstash.config.ir.graph.PlainEdge.new(e.from, outgoing.to))
+          end
+        elsif vertex_type(e.from) == :separator
+          # Skip the edges coming from the 'from' separator
+        else
+          edges_with_separators_removed << edge(e)
+        end
+      end
+      edges_with_separators_removed
+    end
+
     def edge(e)
       e_json = {
         "from" => e.from.id,