lazy module inclusion into DSL moduleslcg/use-and-lazy-module-include

Chef::DSL::Recipe::FullDSL.send(:include, MyModule) will now patch all
its descendants that it has been included into (works the way actual
inheritance works now).

3 files changed, 84 insertions, 3 deletions

diff --git a/lib/chef/dsl/recipe.rb b/lib/chef/dsl/recipe.rb
index 6d254df48d..22be303c5b 100644
--- a/lib/chef/dsl/recipe.rb
+++ b/lib/chef/dsl/recipe.rb
@@ -23,21 +23,21 @@ require "chef/mixin/powershell_out"
 require "chef/dsl/resources"
 require "chef/dsl/definitions"
 require "chef/dsl/declare_resource"
+require "chef/mixin/lazy_module_include"
 
 class Chef
   module DSL
-
     # == Chef::DSL::Recipe
     # Provides the primary recipe DSL functionality for defining Chef resource
     # objects via method calls.
     module Recipe
-
       include Chef::Mixin::ShellOut
       include Chef::Mixin::PowershellOut
 
       include Chef::DSL::Resources
       include Chef::DSL::Definitions
       include Chef::DSL::DeclareResource
+      extend Chef::Mixin::LazyModuleInclude
 
       def resource_class_for(snake_case_name)
         Chef::Resource.resource_for_node(snake_case_name, run_context.node)
@@ -113,6 +113,8 @@ class Chef
         require "chef/dsl/reboot_pending"
         require "chef/dsl/audit"
         require "chef/dsl/powershell"
+        require "chef/mixin/lazy_module_include"
+
         include Chef::DSL::DataQuery
         include Chef::DSL::PlatformIntrospection
         include Chef::DSL::IncludeRecipe
@@ -121,6 +123,9 @@ class Chef
         include Chef::DSL::RebootPending
         include Chef::DSL::Audit
         include Chef::DSL::Powershell
+
+        extend Chef::Mixin::LazyModuleInclude
+
       end
     end
   end
diff --git a/lib/chef/mixin/lazy_module_include.rb b/lib/chef/mixin/lazy_module_include.rb
new file mode 100644
index 0000000000..34e1fce4f1
--- /dev/null
+++ b/lib/chef/mixin/lazy_module_include.rb
@@ -0,0 +1,77 @@
+#
+# Copyright:: Copyright 2011-2016, Chef Software Inc.
+# License:: Apache License, Version 2.0
+#
+# 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.
+#
+
+class Chef
+  module Mixin
+    # If you have:
+    #
+    # module A
+    #   extend LazyModuleInclude
+    # end
+    #
+    # module B
+    #   include A
+    # end
+    #
+    # module C
+    #   include B
+    # end
+    #
+    # module Monkeypatches
+    #   def monkey
+    #     puts "monkey!"
+    #   end
+    # end
+    #
+    # A.send(:include, Monkeypatches)
+    #
+    # Then B and C and any classes that they're included in will also get the #monkey method patched into them.
+    #
+    module LazyModuleInclude
+
+      # Most of the magick is in this hook which creates a closure over the parent class and then builds an
+      # "infector" module which infects all descendants and which is responsible for updating the list of
+      # descendants in the parent class.
+      def included(klass)
+        super
+        parent_klass = self
+        infector = Module.new do
+          define_method(:included) do |subklass|
+            super(subklass)
+            subklass.extend(infector)
+            parent_klass.descendants.push(subklass)
+          end
+        end
+        klass.extend(infector)
+        parent_klass.descendants.push(klass)
+      end
+
+      def descendants
+        @descendants ||= []
+      end
+
+      def include(*classes)
+        super
+        classes.each do |klass|
+          descendants.each do |descendant|
+            descendant.send(:include, klass)
+          end
+        end
+      end
+    end
+  end
+end
diff --git a/lib/chef/recipe.rb b/lib/chef/recipe.rb
index 3a91781b2e..55b6fd7d52 100644
--- a/lib/chef/recipe.rb
+++ b/lib/chef/recipe.rb
@@ -114,6 +114,5 @@ class Chef
         run_context.node.tags.delete(tag)
       end
     end
-
   end
 end