Require a distributor when adding a product to the cart

app/controllers/spree/orders_controller_decorator.rb

@@ -0,0 +1,11 @@
+Spree::OrdersController.class_eval do
+  before_filter :populate_order_distributor, :only => :populate
+
+  def populate_order_distributor
+    @distributor = Spree::Distributor.find params[:distributor_id]
+    if @distributor.nil?
+      return false
+    end
+
+  end
+end

spec/controllers/orders_controller_spec.rb

@@ -0,0 +1,14 @@
+require 'spec_helper'
+
+describe Spree::OrdersController do
+  context "adding the first product to the cart" do
+    it "does nothing if the user does not specify a distributor" do
+      create(:distributor)
+      p = create(:product)
+
+      expect do
+        spree_put :populate, :variants => {p.id => 1}
+      end.to change(Spree::LineItem, :count).by(0)
+    end
+  end
+end