Display shipping fee at all steps of the checkout process, not just after delivery method is chosen

app/models/spree/order_decorator.rb

@@ -1,6 +1,9 @@
 Spree::Order.class_eval do
   belongs_to :distributor
 
+  after_create :set_default_shipping_method
+
+
   def can_change_distributor?
     # Distributor may not be changed once an item has been added to the cart/order
     line_items.empty?
@@ -31,6 +34,20 @@ Spree::Order.class_eval do
   before_validation :shipping_address_from_distributor
 
   private
+
+  # On creation of the order (when the first item is added to the user's cart), set the
+  # shipping method to the first one available and create a shipment.
+  # order.create_shipment! creates an adjustment for the shipping cost on the order,
+  # which means that the customer can see their shipping cost at every step of the
+  # checkout process, not just after the delivery step.
+  # This is based on the assumption that there's only one shipping method visible to the user,
+  # which is a method using the itemwise shipping calculator.
+  def set_default_shipping_method
+    self.shipping_method = Spree::ShippingMethod.where("display_on != 'back_end'").first
+    self.save!
+    self.create_shipment!
+  end
+
   def shipping_address_from_distributor
     if distributor
       self.ship_address = distributor.pickup_address.clone

spec/models/order_spec.rb

@@ -1,6 +1,19 @@
 require 'spec_helper'
 
 describe Spree::Order do
+  it "initialises a default shipping method after creation" do
+    shipping_method_back_end = create(:shipping_method, :display_on => :back_end)
+    shipping_method_both = create(:shipping_method, :display_on => :both)
+
+    subject.shipping_method.should be_nil
+    subject.adjustments.should be_empty
+
+    subject.save!
+
+    subject.shipping_method.should == shipping_method_both
+    subject.adjustments.where(:label => "Shipping").should be_present
+  end
+
   it "reveals permission for changing distributor" do
     p = build(:product)