Restoring enterprise permalinks when they cause errors

app/models/enterprise.rb

@@ -72,6 +72,8 @@ class Enterprise < ActiveRecord::Base
   after_update :welcome_after_confirm, if: lambda { confirmation_token_changed? && confirmation_token.nil? }
   after_create :send_welcome_email, if: lambda { email_is_known? }
 
+  after_rollback :restore_permalink
+
   scope :by_name, order('name')
   scope :visible, where(:visible => true)
   scope :confirmed, where('confirmed_at IS NOT NULL')
@@ -363,4 +365,9 @@ class Enterprise < ActiveRecord::Base
       errors.add(:shopfront_category_ordering, "must contain a list of taxons.")
     end
   end
+
+  def restore_permalink
+    # If the permalink has errors, reset it to it's original value, so we can update the form
+    self.permalink = permalink_was if permalink_changed? && errors[:permalink].present?
+  end
 end

spec/models/enterprise_spec.rb

@@ -223,6 +223,16 @@ describe Enterprise do
     it { should delegate(:state_name).to(:address) }
   end
 
+  describe "callbacks" do
+    it "restores permalink to original value when it is changed and invalid" do
+      e1 = create(:enterprise, permalink: "taken")
+      e2 = create(:enterprise, permalink: "not_taken")
+      e2.permalink = "taken"
+      e2.save
+      expect(e2.permalink).to eq "not_taken"
+    end
+  end
+
   describe "scopes" do
     describe 'visible' do
       it 'find visible enterprises' do