Fix bug on calculator_decorator line_items_for where input is line_it…

…em with an nil order.

Adapted line_items_for so that weight_calculator.line_items_for could be removed.

app/models/calculator/weight.rb

@@ -12,19 +12,5 @@ def compute(object)
       total_weight = line_items.sum { |li| ((li.variant.andand.weight || 0) * li.quantity) }
       total_weight * preferred_per_kg
     end
-
-    private
-
-    def line_items_for(object)
-      if object.respond_to? :order
-        object.order.line_items
-      elsif object.respond_to? :line_items
-        object.line_items
-      elsif object.respond_to?(:variant) && object.respond_to?(:quantity)
-        [object]
-      else
-        raise "Unknown object type: #{object.inspect}"
-      end
-    end
   end
 end

app/models/spree/calculator_decorator.rb

@@ -5,12 +5,14 @@ module Spree
     # Given an object which might be an Order or a LineItem (amongst
     # others), return a collection of line items.
     def line_items_for(object)
-      if object.respond_to? :line_items
+      if object.respond_to?(:variant) && object.respond_to?(:quantity)
+        [object]
+      elsif object.respond_to? :line_items
         object.line_items
-      elsif object.respond_to? :order
+      elsif object.order.present?
         object.order.line_items
       else
-        [object]
+        raise "Could not fetch line_items for #{object.inspect}"
       end
     end
   end

spec/models/spree/calculator/flat_percent_item_total_spec.rb

@@ -2,7 +2,7 @@
 
 describe Spree::Calculator::FlatPercentItemTotal do
   let(:calculator) { Spree::Calculator::FlatPercentItemTotal.new }
-  let(:line_item) { instance_double(Spree::LineItem, amount: 10) }
+  let(:line_item) { build(:line_item) }
 
   before { calculator.stub preferred_flat_percent: 10 }
 

spec/models/spree/calculator/flexi_rate_spec.rb

@@ -1,7 +1,7 @@
 require 'spec_helper'
 
 describe Spree::Calculator::FlexiRate do
-  let(:line_item) { instance_double(Spree::LineItem, amount: 10, quantity: quantity) }
+  let(:line_item) { build(:line_item, quantity: quantity) }
   let(:calculator) do
     Spree::Calculator::FlexiRate.new(
       preferred_first_item: 2,

spec/models/spree/calculator/per_item_spec.rb

@@ -3,7 +3,7 @@
 describe Spree::Calculator::PerItem do
   let(:calculator) { Spree::Calculator::PerItem.new(preferred_amount: 10) }
   let(:shipping_calculable) { double(:calculable) }
-  let(:line_item) { double(:line_item, quantity: 5, product: double(:product)) }
+  let(:line_item) { build(:line_item, quantity: 5) }
 
   it "correctly calculates on a single line item object" do
     calculator.stub(calculable: shipping_calculable)