Change set_variant_attribute to set_variant_attributes, implement it on Order

app/controllers/spree/orders_controller_decorator.rb

@@ -18,9 +18,7 @@ Spree::OrdersController.class_eval do
   def populate_variant_attributes
     if params.key? :variant_attributes
       params[:variant_attributes].each do |variant_id, attributes|
-        attributes.each do |k, v|
-          @order.set_variant_attribute(Spree::Variant.find(variant_id), k, v)
-        end
+        @order.set_variant_attributes(Spree::Variant.find(variant_id), attributes)
       end
     end
   end

app/models/spree/line_item_decorator.rb

@@ -1,4 +1,6 @@
 Spree::LineItem.class_eval do
+  attr_accessible :max_quantity
+
   def shipping_method
     self.product.shipping_method_for_distributor(self.order.distributor)
   end

app/models/spree/order_decorator.rb

@@ -15,6 +15,13 @@ Spree::Order.class_eval do
     can_change_distributor? || product.distributors.include?(distributor)
   end
 
+  def set_variant_attributes(variant, attributes)
+    line_item = contains?(variant)
+
+    line_item.assign_attributes(attributes)
+    line_item.save!
+  end
+
 
 
   before_validation :shipping_address_from_distributor

spec/controllers/orders_controller_spec.rb

@@ -116,7 +116,7 @@ describe Spree::OrdersController do
       p = create(:product, :distributors => [distributor_product], :group_buy => true)
 
       order = current_order(true)
-      order.should_receive(:set_variant_attribute).with(p.master, 'max_quantity', '3')
+      order.should_receive(:set_variant_attributes).with(p.master, {'max_quantity' => '3'})
       controller.stub(:current_order).and_return(order)
 
       expect do

spec/models/order_spec.rb

@@ -46,4 +46,17 @@ describe Spree::Order do
     # And cannot be added if it does not match
     subject.can_add_product_to_cart?(p_subsequent_other_dist).should be_false
   end
+
+  it "sets attributes on line items for variants" do
+    subject.save!
+    d = create(:distributor)
+    p = create(:product, :distributors => [d])
+
+    subject.distributor = d
+    subject.add_variant(p.master, 1)
+    subject.set_variant_attributes(p.master, {'max_quantity' => '3'})
+
+    li = Spree::LineItem.last
+    li.max_quantity.should == 3
+  end
 end