Close adjustments so that updates are effective

Spree 2.0 keeps shipping fee adjustments open unless they are manually
closed. But open adjustments cannot be edited.
To preserve updates, like changing the amount of the shipping fee
we close the adjustment first.

app/controllers/spree/admin/adjustments_controller_decorator.rb

@@ -3,7 +3,7 @@ module Spree
     AdjustmentsController.class_eval do
       prepend_before_filter :set_included_tax, only: [:create, :update]
       before_filter :set_default_tax_rate, only: :edit
-
+      before_filter :enable_updates, only: :update
 
       private
 
@@ -38,6 +38,17 @@ module Spree
           params[:adjustment][:included_tax] = 0
         end
       end
+
+      # Spree 2.0 keeps shipping fee adjustments open unless they are manually
+      # closed. But open adjustments cannot be edited.
+      # To preserve updates, like changing the amount of the shipping fee,
+      # we close the adjustment first.
+      #
+      # The Spree admin interface allows to open and close adjustments manually
+      # but we removed that functionality as it had no purpose for us.
+      def enable_updates
+        @adjustment.close
+      end
     end
   end
 end

spec/features/admin/orders_spec.rb

@@ -350,6 +350,16 @@ feature %q{
           end
         end
       end
+
+      scenario "editing shipping fees" do
+        click_link "Adjustments"
+        page.find('td.actions a.icon-edit').click
+
+        fill_in "Amount", with: "5"
+        click_button "Continue"
+
+        expect(page.find("td.amount")).to have_content "$5.00"
+      end
     end
 
     scenario "creating an order with distributor and order cycle" do