Chef-15: add nillability to attribute deep merging

Changes to consistently uses the "NIL" object internally to mean "not present"
instead of abusing nil for that purpose.

So now "nil means nil" and we can deep merge that so it will effectively
override lower precedence levels if you write a nil.

Signed-off-by: Lamont Granquist <lamont@scriptkiddie.org>

1 files changed, 30 insertions, 0 deletions

diff --git a/spec/unit/node/attribute_spec.rb b/spec/unit/node/attribute_spec.rb
index 36827215f0..c6fdf1e1c2 100644
--- a/spec/unit/node/attribute_spec.rb
+++ b/spec/unit/node/attribute_spec.rb
@@ -1273,4 +1273,34 @@ describe Chef::Node::Attribute do
       expect { @attributes["foo"]["bar"][0] << "buzz" }.to raise_error(RuntimeError, "can't modify frozen String")
     end
   end
+
+  describe "deep merging with nils" do
+    it "nils when deep merging between default levels knocks out values" do
+      @attributes.default["foo"] = "bar"
+      expect(@attributes["foo"]).to eql("bar")
+      @attributes.force_default["foo"] = nil
+      expect(@attributes["foo"]).to be nil
+    end
+
+    it "nils when deep merging between override levels knocks out values" do
+      @attributes.override["foo"] = "bar"
+      expect(@attributes["foo"]).to eql("bar")
+      @attributes.force_override["foo"] = nil
+      expect(@attributes["foo"]).to be nil
+    end
+
+    it "nils when deep merging between default+override levels knocks out values" do
+      @attributes.default["foo"] = "bar"
+      expect(@attributes["foo"]).to eql("bar")
+      @attributes.override["foo"] = nil
+      expect(@attributes["foo"]).to be nil
+    end
+
+    it "nils when deep merging between normal+automatic levels knocks out values" do
+      @attributes.normal["foo"] = "bar"
+      expect(@attributes["foo"]).to eql("bar")
+      @attributes.automatic["foo"] = nil
+      expect(@attributes["foo"]).to be nil
+    end
+  end
 end