Merge pull request #4838 from chef/lcg/resource-cloning-toggle

add global and per-resource toggles for resource cloning behavior

3 files changed, 40 insertions, 2 deletions

diff --git a/chef-config/lib/chef-config/config.rb b/chef-config/lib/chef-config/config.rb
index c9c2ca77df..23e4d75168 100644
--- a/chef-config/lib/chef-config/config.rb
+++ b/chef-config/lib/chef-config/config.rb
@@ -1053,6 +1053,12 @@ module ChefConfig
 
     default :rubygems_url, "https://rubygems.org"
 
+    # This controls the behavior of resource cloning (and CHEF-3694 warnings).  For Chef < 12 the behavior
+    # has been that this is 'true', in Chef 13 this will change to false.  Setting this to 'true' in Chef
+    # 13 is not a viable or supported migration strategy since Chef 13 community cookbooks will be expected
+    # to break with this setting set to 'true'.
+    default :resource_cloning, true
+
     # If installed via an omnibus installer, this gives the path to the
     # "embedded" directory which contains all of the software packaged with
     # omnibus. This is used to locate the cacert.pem file on windows.
diff --git a/lib/chef/resource_builder.rb b/lib/chef/resource_builder.rb
index 78b2fcd4d1..1aee852f5d 100644
--- a/lib/chef/resource_builder.rb
+++ b/lib/chef/resource_builder.rb
@@ -56,7 +56,7 @@ class Chef
       # This behavior is very counter-intuitive and should be removed.
       # See CHEF-3694, https://tickets.opscode.com/browse/CHEF-3694
       # Moved to this location to resolve CHEF-5052, https://tickets.opscode.com/browse/CHEF-5052
-      if prior_resource
+      if prior_resource && Chef::Config[:resource_cloning]
         resource.load_from(prior_resource)
       end
 
@@ -80,7 +80,7 @@ class Chef
       end
 
       # emit a cloned resource warning if it is warranted
-      if prior_resource
+      if prior_resource && Chef::Config[:resource_cloning]
         if is_trivial_resource?(prior_resource) && identicalish_resources?(prior_resource, resource)
           emit_harmless_cloning_debug
         else
diff --git a/spec/unit/recipe_spec.rb b/spec/unit/recipe_spec.rb
index eea1a41998..e1e3e0ad72 100644
--- a/spec/unit/recipe_spec.rb
+++ b/spec/unit/recipe_spec.rb
@@ -193,6 +193,38 @@ describe Chef::Recipe do
       end
     end
 
+    describe "when resource cloning is disabled" do
+      def not_expect_warning
+        expect(Chef::Log).not_to receive(:warn).with(/3694/)
+        expect(Chef::Log).not_to receive(:warn).with(/Previous/)
+        expect(Chef::Log).not_to receive(:warn).with(/Current/)
+      end
+
+      before do
+        Chef::Config[:resource_cloning] = false
+      end
+
+      it "should emit a 3694 warning when attributes change" do
+        recipe.zen_master "klopp" do
+          something "bvb"
+        end
+        not_expect_warning
+        recipe.zen_master "klopp" do
+          something "vbv"
+        end
+      end
+
+      it "should not copy attributes from a prior resource" do
+        recipe.zen_master "klopp" do
+          something "bvb"
+        end
+        not_expect_warning
+        recipe.zen_master "klopp"
+        expect(run_context.resource_collection.first.something).to eql("bvb")
+        expect(run_context.resource_collection[1].something).to be nil
+      end
+    end
+
     describe "when cloning resources" do
       def expect_warning
         expect(Chef).to receive(:deprecated).with(:resource_cloning, /^Cloning resource attributes for zen_master\[klopp\]/)