Add optimistic locking to user stories

app/controllers/user_stories_controller.rb

@@ -62,6 +62,9 @@ def update
       render 'edit' and return false
     end
     redirect_back_or(project_backlog_index_path(@project))
+  rescue ActiveRecord::StaleObjectError
+    flash.now[:error] = "Another person has just updated that record"
+    render 'edit'
   end
 
   def plan
@@ -115,7 +118,15 @@ def user_story_must_exist
   end
 
   def user_story_params
-    params[:user_story].permit(:definition, :story_points, :stakeholder, :cannot_be_estimated, :description, { acceptance_criteria_attributes: [:id, :detail, :_destroy]}, {tasks_attributes: [:id, :definition, :description, :_destroy]})
+    params[:user_story].permit(
+      :lock_version,
+      :definition,
+      :story_points,
+      :stakeholder,
+      :cannot_be_estimated,
+      :description,
+      acceptance_criteria_attributes: [:id, :detail, :_destroy],
+      tasks_attributes: [:id, :definition, :description, :_destroy])
   end
 
   def save_or_close_path(commit_param)

app/views/user_stories/_form.html.erb

@@ -2,6 +2,7 @@
   <div class="row">
 
     <div class="large-15 small-24 medium-24 columns">
+      <%= f.input :lock_version, as: 'hidden' %>
       <%= f.input :definition, input_html: {rows: 5, placeholder: 'As a user I want blink tags around key navigation items so I can find them quicker...'} %>
       <div class="row">
         <div class="large-10 small-10 medium-10 columns">

db/migrate/20150820113718_add_lock_version_to_user_stories.rb

@@ -0,0 +1,5 @@
+class AddLockVersionToUserStories < ActiveRecord::Migration
+  def change
+    add_column :user_stories, :lock_version, :integer, default: 0
+  end
+end

db/schema.rb

@@ -11,7 +11,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 20150217161258) do
+ActiveRecord::Schema.define(version: 20150820113718) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
@@ -90,13 +90,12 @@
   add_index "people", ["unsubscribe_token"], name: "index_people_on_unsubscribe_token", using: :btree
 
   create_table "projects", force: :cascade do |t|
-    t.string   "name",                            null: false
+    t.string   "name",             null: false
     t.integer  "iteration_length"
     t.integer  "velocity"
-    t.datetime "created_at",                      null: false
-    t.datetime "updated_at",                      null: false
+    t.datetime "created_at",       null: false
+    t.datetime "updated_at",       null: false
     t.datetime "deleted_at"
-    t.boolean  "use_estimates",    default: true
   end
 
   add_index "projects", ["name"], name: "index_projects_on_name", unique: true, using: :btree
@@ -184,6 +183,7 @@
     t.string   "stakeholder",         default: ""
     t.boolean  "delta",               default: false
     t.integer  "project_id"
+    t.integer  "lock_version",        default: 0
   end
 
   add_index "user_stories", ["project_id", "sprint_id"], name: "index_user_stories_on_project_id_and_sprint_id", using: :btree

spec/features/edit_user_story_spec.rb

@@ -1,6 +1,6 @@
-require 'rails_helper'
+require "rails_helper"
 
-RSpec.feature 'Editing a user story', type: :feature do
+RSpec.feature "Editing a user story", type: :feature do
 
   before do
     @user = create_person
@@ -11,10 +11,20 @@
 
   it "edits a user story" do
     visit "/projects/#{@project.id}/user_stories/#{@user_story.id}/edit"
-    fill_in 'user_story_definition', :with => 'As a user I want beef to eat'
-    click_button 'Save and Close'
-    expect(page).to have_content 'User story updated successfully'
-    expect(page).to have_content 'As a user I want beef to eat'
+    fill_in "user_story_definition", with: "As a user I want beef to eat"
+    click_button "Save and Close"
+    expect(page).to have_content "User story updated successfully"
+    expect(page).to have_content "As a user I want beef to eat"
+  end
+
+  it "fails if someone else edits in the meantime" do
+    error = ActiveRecord::StaleObjectError.new(@user_story, :update)
+    allow_any_instance_of(UserStory).
+      to receive(:update_attributes).and_raise(error)
+    visit "/projects/#{@project.id}/user_stories/#{@user_story.id}/edit"
+    fill_in "user_story_definition", with: "As a user I want beef to eat"
+    click_button "Save and Close"
+    expect(page).to have_content "Another person has just updated that record"
   end
 
   it "should prefill stakeholder" do