turbo attribute merging

Signed-off-by: Lamont Granquist <lamont@scriptkiddie.org>

1 files changed, 16 insertions, 1 deletions

diff --git a/lib/chef/node/immutable_collections.rb b/lib/chef/node/immutable_collections.rb
index 13cb321890..3378bee2b5 100644
--- a/lib/chef/node/immutable_collections.rb
+++ b/lib/chef/node/immutable_collections.rb
@@ -198,6 +198,7 @@ class Chef
     class ImmutableMash < Mash
       alias_method :internal_clear, :clear
       alias_method :internal_key?, :key? # FIXME: could bypass convert_key in Mash for perf
+      alias_method :internal_each, :each
 
       include Immutablize
       include CommonAPI
@@ -264,6 +265,7 @@ class Chef
 
       def reset
         @generated_cache = false
+        @short_circuit_attr_level = nil
         internal_clear # redundant?
       end
 
@@ -273,13 +275,20 @@ class Chef
         @generated_cache = true
       end
 
+      # @api private
+      attr_accessor :short_circuit_attr_levels
+
       private
 
       def generate_cache
         internal_clear
-        Attribute::COMPONENTS.reverse.each do |component|
+        components = short_circuit_attr_levels ? short_circuit_attr_levels : Attribute::COMPONENTS.reverse
+        # merged_components is not entirely accurate due to the short-circuit
+        merged_components = []
+        components.each do |component|
           subhash = __node__.attributes.instance_variable_get(component).read(*__path__)
           unless subhash.nil? # FIXME: nil is used for not present
+            merged_components << component
             if subhash.kind_of?(Hash)
               subhash.keys.each do |key|
                 next if internal_key?(key)
@@ -290,6 +299,12 @@ class Chef
             end
           end
         end
+        if merged_components.size == 1
+          # merged_components is accurate enough to tell us if we're not really merging
+          internal_each do |key, value|
+            value.short_circuit_attr_levels = merged_components if value.respond_to?(:short_circuit_attr_levels)
+          end
+        end
       end
 
       prepend Chef::Node::Mixin::StateTracking