add Chef/NodeSet cop with autocorrect

autocorrects to node.normal.

we need a Chef/NodeNormal to warn about that, but this is a tiny bit
of progress.

config/cookstyle.yml

@@ -24,6 +24,9 @@ AllCops:
   ChefResources:
     Patterns:
     - resources/.*\.rb
+  NodeSet:
+    Patterns:
+    - .*\.rb
 
 Chef/AttributeKeys:
   Description: Check which style of keys are used to access node attributes.
@@ -49,6 +52,10 @@ Chef/CommentFormat:
   Description: Use Chef's unique format for comment headers
   Enabled: true
 
+Chef/NodeSet:
+  Description: Do not use node.set
+  Enabled: true
+
 #### The base rubocop 0.37 enabled.yml file we started with ####
 
 Layout/AccessModifierIndentation:

lib/cookstyle.rb

@@ -34,9 +34,7 @@ def self.config
 require 'rubocop/chef/cookbook_only'
 
 # Chef specific cops
-require 'rubocop/cop/chef/attribute_keys'
-require 'rubocop/cop/chef/file_mode'
-require 'rubocop/cop/chef/service_resource'
-require 'rubocop/cop/chef/comments_format'
-require 'rubocop/cop/chef/comments_copyright_format'
-require 'rubocop/cop/chef/tmp_path'
+Dir.glob(File.dirname(__FILE__) + "/rubocop/cop/chef/**/*.rb") do |file|
+  next if File.directory?(file)
+  require_relative file # not actually relative but require_relative is faster
+end

lib/rubocop/cop/chef/node_set.rb

@@ -0,0 +1,53 @@
+#
+# Copyright:: Copyright 2001-2019, Chef Software Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+module RuboCop
+  module Cop
+    module Chef
+      # The node.set method has been removed in Chef-13 and must be replaced by node.normal.
+      #
+      # Note that node.normal keeps the semantics identical, but the use of node.normal is
+      # also discouraged.
+      #
+      # @example
+      #
+      #   # bad
+      #   node.set['foo'] = true
+      #
+      #   # good
+      #   node.normal['foo'] = true
+      #
+      class NodeSet < Cop
+        MSG = 'Do not use node.set'.freeze
+
+        def_node_matcher :node_set?, <<-PATTERN
+          (send (send _ :node) :set)
+        PATTERN
+
+        def on_send(node)
+          node_set?(node) do
+            add_offense(node, location: :expression, message: MSG, severity: :error)
+          end
+        end
+
+        def autocorrect(node)
+          lambda do |corrector|
+            corrector.replace(node.loc.expression, "node.normal")
+          end
+        end
+      end
+    end
+  end
+end