Cart compatibility upgrade

app/controllers/application_controller.rb

@@ -18,6 +18,7 @@ class ApplicationController < ActionController::Base
     c.before_filter :fix_cart_date
     c.before_filter :set_view_mode
     c.before_filter :check_view_mode
+    c.before_filter :make_cart_compatible
   end
 
   helper_method :current_user
@@ -114,6 +115,15 @@ def fix_cart_date
     cart.fix_due_date
   end
 
+  # If user's session has an old Cart object that stores items in Array rather
+  # than a Hash (see #587), regenerate the Cart.
+  # TODO: Remove in ~2015, when nobody could conceivably run the old app?
+  def make_cart_compatible
+    if session[:cart].items.is_a? Array
+      session[:cart] = Cart.new
+    end
+  end
+
   #-------- end before_filter methods --------#
 
   def update_cart

spec/controllers/application_controller_spec.rb

@@ -48,6 +48,24 @@ def method_requiring_user
     controller.stub(:fix_cart_date)
     controller.stub(:set_view_mode)
     controller.stub(:current_user)
+    controller.stub(:make_cart_compatible)
+  end
+
+  describe 'make_cart_compatible' do
+    before(:each) do
+      controller.unstub(:make_cart_compatible)
+    end
+    it 'replaces the cart if items is an Array' do
+      session[:cart] = FactoryGirl.build(:cart, items: [1])
+      get :index
+      session[:cart].items.should be_a(Hash)
+      session[:cart].items.should be_empty
+      session[:cart].items.should_not be_a(Array)
+    end
+    it 'leaves the cart alone if items is a Hash' do
+      session[:cart] = FactoryGirl.build(:cart_with_items)
+      expect { get :index }.to_not change { session[:cart].items }
+    end
   end
 
   describe 'app_setup_check' do
@@ -243,6 +261,7 @@ def method_requiring_user
     controller.stub(:fix_cart_date)
     controller.stub(:set_view_mode)
     controller.stub(:current_user)
+    controller.stub(:make_cart_compatible)
   end
 
   #TODO - This may involve rewriting the method somewhat