1 files changed, 71 insertions, 4 deletions

diff --git a/lib/chef/node/attribute.rb b/lib/chef/node/attribute.rb
index 6130925aea..3c48f653eb 100644
--- a/lib/chef/node/attribute.rb
+++ b/lib/chef/node/attribute.rb
@@ -175,6 +175,19 @@ class Chef
        # return the automatic level attribute component
        attr_reader :automatic
 
+       # This is used to track the top level key as we descend through method chaining into
+       # a precedence level (e.g. node.default['foo']['bar']['baz']= results in 'foo' here).  We
+       # need this so that when we hit the end of a method chain which results in a mutator method
+       # that we can invalidate the whole top-level deep merge cache for the top-level key.  It is
+       # the responsibility of the accessor on the Chef::Node object to reset this to nil, and then
+       # the first VividMash#[] call can ||= and set this to the first key we encounter.
+       attr_accessor :top_level_breadcrumb
+
+       # Cache of deep merged values by top-level key.  This is a simple hash which has keys that are the
+       # top-level keys of the node object, and we save the computed deep-merge for that key here.  There is
+       # no cache of subtrees.
+       attr_accessor :deep_merge_cache
+
        def initialize(normal, default, override, automatic)
          @set_unless_present = false
 
@@ -195,6 +208,8 @@ class Chef
          @merged_attributes = nil
          @combined_override = nil
          @combined_default = nil
+         @top_level_breadcrumb = nil
+         @deep_merge_cache = {}
        end
 
        # Debug what's going on with an attribute. +args+ is a path spec to the
@@ -230,51 +245,75 @@ class Chef
          @set_unless_present = setting
        end
 
+       # Invalidate a key in the deep_merge_cache.  If called with nil, or no arg, this will invalidate
+       # the entire deep_merge cache.  In the case of the user doing node.default['foo']['bar']['baz']=
+       # that eventually results in a call to reset_cache('foo') here.  A node.default=hash_thing call
+       # must invalidate the entire cache and re-deep-merge the entire node object.
+       def reset_cache(path = nil)
+         if path.nil?
+           @deep_merge_cache = {}
+         else
+           deep_merge_cache.delete(path)
+         end
+       end
+
+       alias :reset :reset_cache
+
        # Set the cookbook level default attribute component to +new_data+.
        def default=(new_data)
+         reset
          @default = VividMash.new(self, new_data)
        end
 
        # Set the role level default attribute component to +new_data+
        def role_default=(new_data)
+         reset
          @role_default = VividMash.new(self, new_data)
        end
 
        # Set the environment level default attribute component to +new_data+
        def env_default=(new_data)
+         reset
          @env_default = VividMash.new(self, new_data)
        end
 
        # Set the force_default (+default!+) level attributes to +new_data+
        def force_default=(new_data)
+         reset
          @force_default = VividMash.new(self, new_data)
        end
 
        # Set the normal level attribute component to +new_data+
        def normal=(new_data)
+         reset
          @normal = VividMash.new(self, new_data)
        end
 
        # Set the cookbook level override attribute component to +new_data+
        def override=(new_data)
+         reset
          @override = VividMash.new(self, new_data)
        end
 
        # Set the role level override attribute component to +new_data+
        def role_override=(new_data)
+         reset
          @role_override = VividMash.new(self, new_data)
        end
 
        # Set the environment level override attribute component to +new_data+
        def env_override=(new_data)
+         reset
          @env_override = VividMash.new(self, new_data)
        end
 
        def force_override=(new_data)
+         reset
          @force_override = VividMash.new(self, new_data)
        end
 
        def automatic=(new_data)
+         reset
          @automatic = VividMash.new(self, new_data)
        end
 
@@ -284,6 +323,7 @@ class Chef
 
        # clears attributes from all precedence levels
        def rm(*args)
+         reset(args[0])
          # just easier to compute our retval, rather than collect+merge sub-retvals
          ret = args.inject(merged_attributes) do |attr, arg|
            if attr.nil? || !attr.respond_to?(:[])
@@ -314,6 +354,7 @@ class Chef
        #
        # equivalent to: force_default!['foo']['bar'].delete('baz')
        def rm_default(*args)
+         reset(args[0])
          remove_from_precedence_level(force_default!(autovivify: false), *args)
        end
 
@@ -321,6 +362,7 @@ class Chef
        #
        # equivalent to: normal!['foo']['bar'].delete('baz')
        def rm_normal(*args)
+         reset(args[0])
          remove_from_precedence_level(normal!(autovivify: false), *args)
        end
 
@@ -328,6 +370,7 @@ class Chef
        #
        # equivalent to: force_override!['foo']['bar'].delete('baz')
        def rm_override(*args)
+         reset(args[0])
          remove_from_precedence_level(force_override!(autovivify: false), *args)
        end
 
@@ -337,35 +380,51 @@ class Chef
 
        # sets default attributes without merging
        def default!(opts={})
+         # FIXME: do not flush whole cache
+         reset
          MultiMash.new(self, @default, [], opts)
        end
 
        # sets normal attributes without merging
        def normal!(opts={})
+         # FIXME: do not flush whole cache
+         reset
          MultiMash.new(self, @normal, [], opts)
        end
 
        # sets override attributes without merging
        def override!(opts={})
+         # FIXME: do not flush whole cache
+         reset
          MultiMash.new(self, @override, [], opts)
        end
 
        # clears from all default precedence levels and then sets force_default
        def force_default!(opts={})
+         # FIXME: do not flush whole cache
+         reset
          MultiMash.new(self, @force_default, [@default, @env_default, @role_default], opts)
        end
 
        # clears from all override precedence levels and then sets force_override
        def force_override!(opts={})
+         # FIXME: do not flush whole cache
+         reset
          MultiMash.new(self, @force_override, [@override, @env_override, @role_override], opts)
        end
 
        #
-       # Accessing merged attributes
+       # Accessing merged attributes.
+       #
+       # Note that merged_attributes('foo', 'bar', 'baz') can be called to compute only the
+       # deep merge of node['foo']['bar']['baz'], but in practice we currently always compute
+       # all of node['foo'] even if the user only requires node['foo']['bar']['baz'].
        #
 
        def merged_attributes(*path)
-         immutablize(merge_all(path))
+        # immutablize(
+           merge_all(path)
+        # )
        end
 
        def combined_override(*path)
@@ -377,7 +436,13 @@ class Chef
        end
 
        def [](key)
-         merged_attributes(key)
+         if deep_merge_cache.has_key?(key)
+           # return the cache of the deep merged values by top-level key
+           deep_merge_cache[key]
+         else
+           # save all the work of computing node[key]
+           deep_merge_cache[key] = merged_attributes(key)
+         end
        end
 
        def []=(key, value)
@@ -480,7 +545,9 @@ class Chef
            safe_dup(component)
          end
 
-         components.inject(nil) do |merged, component|
+         return nil if components.compact.empty?
+
+         components.inject(ImmutableMash.new({})) do |merged, component|
            Chef::Mixin::DeepMerge.hash_only_merge!(merged, component)
          end
        end