Use display_as as option value for variant when it is present

app/models/spree/variant_decorator.rb

@@ -56,9 +56,8 @@ Spree::Variant.class_eval do
     delete_unit_option_values
 
     option_type = self.product.variant_unit_option_type
-    option_value_namer = OpenFoodNetwork::OptionValueNamer.new self
     if option_type
-      name = option_value_namer.name
+      name = option_value_name
       ov = Spree::OptionValue.where(option_type_id: option_type, name: name, presentation: name).first || Spree::OptionValue.create!({option_type: option_type, name: name, presentation: name}, without_protection: true)
       option_values << ov
     end

spec/models/spree/variant_spec.rb

@@ -229,6 +229,26 @@ module Spree
         end
       end
 
+      context "when the variant already has a value set (and all required option values exist)" do
+        let!(:p0) { create(:simple_product, variant_unit: 'weight', variant_unit_scale: 1) }
+        let!(:v0) { create(:variant, product: p0, unit_value: 10, unit_description: 'foo') }
+
+        let!(:p) { create(:simple_product, variant_unit: 'weight', variant_unit_scale: 1) }
+        let!(:v) { create(:variant, product: p, unit_value: 5, unit_description: 'bar') }
+
+        it "removes the old option value and assigns the new one" do
+          ov_orig = v.option_values.last
+          ov_new  = v0.option_values.last
+
+          expect {
+            v.update_attributes!(unit_value: 10, unit_description: 'foo')
+          }.to change(Spree::OptionValue, :count).by(0)
+
+          v.option_values.should_not include ov_orig
+          v.option_values.should     include ov_new
+        end
+      end
+
       context "when the variant does not have a display_as value set" do
         let!(:p) { create(:simple_product, variant_unit: 'weight', variant_unit_scale: 1) }
         let!(:v) { create(:variant, product: p, unit_value: 5, unit_description: 'bar', display_as: '') }