Fix for #3382 -- Empty classes as graph placeholders

As Brice discovered, the problem was that we simply ignored empty classes in
the graph when determining application order.  This patch instead replaces them
with a resource of a new type which we've frequently noted the (internal) need
for: a whit, the smallest possible resource, which has no properties or other
semantics apart from its existence and its name.

This resource then ensures application order through the normal mechanisms.

2 files changed, 11 insertions, 5 deletions

diff --git a/lib/puppet/simple_graph.rb b/lib/puppet/simple_graph.rb
index 945b1beb3..55b39fadf 100644
--- a/lib/puppet/simple_graph.rb
+++ b/lib/puppet/simple_graph.rb
@@ -318,16 +318,15 @@ class Puppet::SimpleGraph
     # to container leaves, but that would result in many more
     # relationships.
     stage_class = Puppet::Type.type(:stage)
+    whit_class  = Puppet::Type.type(:whit)
     containers = other.topsort.find_all { |v| (v.is_a?(type) or v.is_a?(stage_class)) and vertex?(v) }
     containers.each do |container|
       # Get the list of children from the other graph.
       children = other.adjacent(container, :direction => :out)
 
-      # Just remove the container if it's empty.
-      if children.empty?
-        remove_vertex!(container)
-        next
-      end
+      # MQR TODO: Luke suggests that it should be possible to refactor the system so that
+      #           container nodes are retained, thus obviating the need for the whit. 
+      children = [whit_class.new(:name => container.name, :catalog => other)] if children.empty?
 
       # First create new edges for each of the :in edges
       [:in, :out].each do |dir|
diff --git a/lib/puppet/type/whit.rb b/lib/puppet/type/whit.rb
new file mode 100644
index 000000000..6e5ba9eab
--- /dev/null
+++ b/lib/puppet/type/whit.rb
@@ -0,0 +1,7 @@
+Puppet::Type.newtype(:whit) do
+  desc "The smallest possible resource type, for when you need a resource and naught else."
+
+  newparam :name do
+    desc "The name of the whit, because it must have one."
+  end
+end