Fix an issue where DeepMerge overwrites nil values

When run against a VividMash.

Call .key? instead of [] when checking if a key exists for a VividMash
Otherwise the VividMash will return an empty object instead of nil for
that key.

Signed-off-by: DJ Mountney <[email protected]>

Author: twk3

lib/chef/mixin/deep_merge.rb

@@ -64,7 +64,7 @@ def deep_merge!(source, dest)
         when Hash
           if dest.kind_of?(Hash)
             source.each do |src_key, src_value|
-              if dest[src_key]
+              if dest.key?(src_key)
                 dest[src_key] = deep_merge!(src_value, dest[src_key])
               else # dest[src_key] doesn't exist so we take whatever source has
                 dest[src_key] = src_value

spec/unit/node_spec.rb

@@ -337,6 +337,13 @@
         node.override_unless[:decontamination] = "foo"
         expect(node.override[:decontamination]).to eql("foo")
       end
+
+      it "consume_attributes does not exhibit chef/chef/issues/6302 bug" do
+        node.normal["a"]["r1"] = nil
+        node.consume_attributes({"a" => { "r2" => nil}})
+        expect(node["a"]["r1"]).to be_nil
+        expect(node["a"]["r2"]).to be_nil
+      end
     end
 
     describe "default attributes" do