Merge branch 'lock_for_issuable' into 'master'

Optimistic locking for Issue and Merge Requests

## What does this MR do?

It implements Optimistic Locking http://api.rubyonrails.org/classes/ActiveRecord/Locking/Optimistic.html for Issues and MRs but in a bit custom way. We use it for cases when either title or description field is involved in the change.

## Why was this MR needed?

We have to prevent data losing.

## What are the relevant issue numbers?
https://gitlab.com/gitlab-org/gitlab-ce/issues/12940

## Screenshots (if relevant)

![Screen_Shot_2016-07-09_at_15.33.02](/uploads/2efbe547a12fda93bce347fa711438d7/Screen_Shot_2016-07-09_at_15.33.02.png)


See merge request !5146

10 files changed, 78 insertions, 14 deletions

diff --git a/CHANGELOG b/CHANGELOG
index 2ad8460731e..a50edf1a797 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -82,6 +82,7 @@ v 8.10.0 (unreleased)
   - Remove duplicate `description` field in `MergeRequest` entities (Ben Boeckel)
   - Style of import project buttons were fixed in the new project page. !5183 (rdemirbay)
   - Fix GitHub client requests when rate limit is disabled
+  - Optimistic locking for Issues and Merge Requests (Title and description overriding prevention)
 
 v 8.9.6 (unreleased)
   - Fix importing of events under notes for GitLab projects
diff --git a/app/controllers/projects/issues_controller.rb b/app/controllers/projects/issues_controller.rb
index b6e80762e3c..f7ada5cfee4 100644
--- a/app/controllers/projects/issues_controller.rb
+++ b/app/controllers/projects/issues_controller.rb
@@ -119,6 +119,10 @@ class Projects::IssuesController < Projects::ApplicationController
         render json: @issue.to_json(include: { milestone: {}, assignee: { methods: :avatar_url }, labels: { methods: :text_color } })
       end
     end
+
+  rescue ActiveRecord::StaleObjectError
+    @conflict = true
+    render :edit
   end
 
   def referenced_merge_requests
@@ -216,7 +220,7 @@ class Projects::IssuesController < Projects::ApplicationController
   def issue_params
     params.require(:issue).permit(
       :title, :assignee_id, :position, :description, :confidential,
-      :milestone_id, :due_date, :state_event, :task_num, label_ids: []
+      :milestone_id, :due_date, :state_event, :task_num, :lock_version, label_ids: []
     )
   end
 
diff --git a/app/controllers/projects/merge_requests_controller.rb b/app/controllers/projects/merge_requests_controller.rb
index df659bb8c3b..2deb7959700 100644
--- a/app/controllers/projects/merge_requests_controller.rb
+++ b/app/controllers/projects/merge_requests_controller.rb
@@ -196,6 +196,9 @@ class Projects::MergeRequestsController < Projects::ApplicationController
     else
       render "edit"
     end
+  rescue ActiveRecord::StaleObjectError
+    @conflict = true
+    render :edit
   end
 
   def remove_wip
@@ -424,7 +427,7 @@ class Projects::MergeRequestsController < Projects::ApplicationController
       :title, :assignee_id, :source_project_id, :source_branch,
       :target_project_id, :target_branch, :milestone_id,
       :state_event, :description, :task_num, :force_remove_source_branch,
-      label_ids: []
+      :lock_version, label_ids: []
     )
   end
 
diff --git a/app/models/concerns/issuable.rb b/app/models/concerns/issuable.rb
index acb6f5a2998..fb49bd7dd64 100644
--- a/app/models/concerns/issuable.rb
+++ b/app/models/concerns/issuable.rb
@@ -87,6 +87,12 @@ module Issuable
       User.find(assignee_id_was).update_cache_counts if assignee_id_was
       assignee.update_cache_counts if assignee
     end
+
+    # We want to use optimistic lock for cases when only title or description are involved
+    # http://api.rubyonrails.org/classes/ActiveRecord/Locking/Optimistic.html
+    def locking_enabled?
+      title_changed? || description_changed?
+    end
   end
 
   module ClassMethods
diff --git a/app/views/shared/issuable/_form.html.haml b/app/views/shared/issuable/_form.html.haml
index c30bdb0ae91..98bbb12eaec 100644
--- a/app/views/shared/issuable/_form.html.haml
+++ b/app/views/shared/issuable/_form.html.haml
@@ -1,5 +1,12 @@
 = form_errors(issuable)
 
+- if @conflict
+  .alert.alert-danger
+    Someone edited the #{issuable.class.model_name.human.downcase} the same time you did.
+    Please check out
+    = link_to "the #{issuable.class.model_name.human.downcase}", polymorphic_path([@project.namespace.becomes(Namespace), @project, issuable]), target: "_blank"
+    and make sure your changes will not unintentionally remove theirs
+
 .form-group
   = f.label :title, class: 'control-label'
   .col-sm-10
@@ -149,3 +156,5 @@
         = link_to 'Delete', polymorphic_path([@project.namespace.becomes(Namespace), @project, issuable]), data: { confirm: "#{issuable.class.name.titleize} will be removed! Are you sure?" },
                                                                                                   method: :delete, class: 'btn btn-danger btn-grouped'
       = link_to 'Cancel', polymorphic_path([@project.namespace.becomes(Namespace), @project, issuable]), class: 'btn btn-grouped btn-cancel'
+
+= f.hidden_field :lock_version
diff --git a/db/migrate/20160707104333_add_lock_to_issuables.rb b/db/migrate/20160707104333_add_lock_to_issuables.rb
new file mode 100644
index 00000000000..cb516672800
--- /dev/null
+++ b/db/migrate/20160707104333_add_lock_to_issuables.rb
@@ -0,0 +1,17 @@
+# See http://doc.gitlab.com/ce/development/migration_style_guide.html
+# for more information on how to write migrations for GitLab.
+
+class AddLockToIssuables < ActiveRecord::Migration
+  include Gitlab::Database::MigrationHelpers
+  disable_ddl_transaction!
+
+  def up
+    add_column_with_default :issues, :lock_version, :integer, default: 0
+    add_column_with_default :merge_requests, :lock_version, :integer, default: 0
+  end
+
+  def down
+    remove_column :issues, :lock_version
+    remove_column :merge_requests, :lock_version
+  end
+end
diff --git a/db/schema.rb b/db/schema.rb
index a5eea3a697c..9d31947d80f 100644
--- a/db/schema.rb
+++ b/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: 20160705163108) do
+ActiveRecord::Schema.define(version: 20160707104333) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
@@ -70,11 +70,11 @@ ActiveRecord::Schema.define(version: 20160705163108) do
     t.string   "recaptcha_site_key"
     t.string   "recaptcha_private_key"
     t.integer  "metrics_port",                          default: 8089
-    t.boolean  "akismet_enabled",                       default: false
-    t.string   "akismet_api_key"
     t.integer  "metrics_sample_interval",               default: 15
     t.boolean  "sentry_enabled",                        default: false
     t.string   "sentry_dsn"
+    t.boolean  "akismet_enabled",                       default: false
+    t.string   "akismet_api_key"
     t.boolean  "email_author_in_body",                  default: false
     t.integer  "default_group_visibility"
     t.boolean  "repository_checks_enabled",             default: false
@@ -84,10 +84,10 @@ ActiveRecord::Schema.define(version: 20160705163108) do
     t.string   "health_check_access_token"
     t.boolean  "send_user_confirmation_email",          default: false
     t.integer  "container_registry_token_expire_delay", default: 5
-    t.boolean  "user_default_external",                 default: false,        null: false
     t.text     "after_sign_up_text"
     t.string   "repository_storage",                    default: "default"
     t.string   "enabled_git_access_protocol"
+    t.boolean  "user_default_external",                 default: false,       null: false
   end
 
   create_table "audit_events", force: :cascade do |t|
@@ -165,8 +165,8 @@ ActiveRecord::Schema.define(version: 20160705163108) do
     t.text     "artifacts_metadata"
     t.integer  "erased_by_id"
     t.datetime "erased_at"
-    t.string   "environment"
     t.datetime "artifacts_expire_at"
+    t.string   "environment"
     t.integer  "artifacts_size"
   end
 
@@ -481,10 +481,11 @@ ActiveRecord::Schema.define(version: 20160705163108) do
     t.string   "state"
     t.integer  "iid"
     t.integer  "updated_by_id"
+    t.integer  "moved_to_id"
     t.boolean  "confidential",  default: false
     t.datetime "deleted_at"
     t.date     "due_date"
-    t.integer  "moved_to_id"
+    t.integer  "lock_version",  default: 0,     null: false
   end
 
   add_index "issues", ["assignee_id"], name: "index_issues_on_assignee_id", using: :btree
@@ -624,6 +625,7 @@ ActiveRecord::Schema.define(version: 20160705163108) do
     t.integer  "merge_user_id"
     t.string   "merge_commit_sha"
     t.datetime "deleted_at"
+    t.integer  "lock_version",              default: 0,     null: false
   end
 
   add_index "merge_requests", ["assignee_id"], name: "index_merge_requests_on_assignee_id", using: :btree
@@ -773,10 +775,10 @@ ActiveRecord::Schema.define(version: 20160705163108) do
     t.integer  "user_id",                    null: false
     t.string   "token",                      null: false
     t.string   "name",                       null: false
-    t.datetime "created_at",                 null: false
-    t.datetime "updated_at",                 null: false
     t.boolean  "revoked",    default: false
     t.datetime "expires_at"
+    t.datetime "created_at",                 null: false
+    t.datetime "updated_at",                 null: false
   end
 
   add_index "personal_access_tokens", ["token"], name: "index_personal_access_tokens_on_token", unique: true, using: :btree
@@ -896,9 +898,9 @@ ActiveRecord::Schema.define(version: 20160705163108) do
     t.string   "type"
     t.string   "title"
     t.integer  "project_id"
-    t.datetime "created_at"
-    t.datetime "updated_at"
-    t.boolean  "active",                default: false,    null: false
+    t.datetime "created_at",                               null: false
+    t.datetime "updated_at",                               null: false
+    t.boolean  "active",                                   null: false
     t.text     "properties"
     t.boolean  "template",              default: false
     t.boolean  "push_events",           default: true
diff --git a/features/project/merge_requests.feature b/features/project/merge_requests.feature
index 21768c15c17..8176ec5ab45 100644
--- a/features/project/merge_requests.feature
+++ b/features/project/merge_requests.feature
@@ -89,7 +89,7 @@ Feature: Project Merge Requests
     Then The list should be sorted by "Oldest updated"
 
   @javascript
-  Scenario: Visiting Merge Requests from a differente Project after sorting
+  Scenario: Visiting Merge Requests from a different Project after sorting
     Given I visit project "Shop" merge requests page
     And I sort the list by "Oldest updated"
     And I visit dashboard merge requests page
diff --git a/spec/features/issues_spec.rb b/spec/features/issues_spec.rb
index d51c9abea19..cfe6349a1a1 100644
--- a/spec/features/issues_spec.rb
+++ b/spec/features/issues_spec.rb
@@ -121,6 +121,17 @@ describe 'Issues', feature: true do
           expect(page).to have_content date.to_s(:medium)
         end
       end
+
+      it 'warns about version conflict' do
+        issue.update(title: "New title")
+
+        fill_in 'issue_title', with: 'bug 345'
+        fill_in 'issue_description', with: 'bug description'
+
+        click_button 'Save changes'
+
+        expect(page).to have_content 'Someone edited the issue the same time you did'
+      end
     end
   end
 
diff --git a/spec/features/merge_requests/edit_mr_spec.rb b/spec/features/merge_requests/edit_mr_spec.rb
index 9e007ab7635..8ad884492d1 100644
--- a/spec/features/merge_requests/edit_mr_spec.rb
+++ b/spec/features/merge_requests/edit_mr_spec.rb
@@ -17,5 +17,16 @@ feature 'Edit Merge Request', feature: true do
     it 'form should have class js-quick-submit' do
       expect(page).to have_selector('.js-quick-submit')
     end
+
+    it 'warns about version conflict' do
+      merge_request.update(title: "New title")
+
+      fill_in 'merge_request_title', with: 'bug 345'
+      fill_in 'merge_request_description', with: 'bug description'
+
+      click_button 'Save changes'
+
+      expect(page).to have_content 'Someone edited the merge request the same time you did'
+    end
   end
 end