From 0feff6c97003ad7f5b1e240b96308b47d1ae8041 Mon Sep 17 00:00:00 2001
From: Robert Machmer <robert.machmer@gmail.com>
Date: Tue, 12 Jan 2016 01:57:23 +0100
Subject: [PATCH] Check if target nodes exist when an edge is added

---
 fd/Graph.lua | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fd/Graph.lua b/fd/Graph.lua
index 6ac7fa6..7e5b46c 100644
--- a/fd/Graph.lua
+++ b/fd/Graph.lua
@@ -96,6 +96,8 @@ function Graph.new()
     -- @param target - The node id to which the edge is pointing to.
     --
     function self:connectIDs( originID, targetID )
+        assert( nodes[originID], string.format( "Tried to add an Edge to the nonexistent Node \"%s\".", originID ));
+        assert( nodes[targetID], string.format( "Tried to add an Edge to the nonexistent Node \"%s\".", targetID ));
         addEdge( nodes[originID], nodes[targetID] );
     end