Exclude projects pending delete from notifications

If the Sidekiq job fails for some reason, a project can be 'stuck'
pending deletion. The project can't be viewed, so it shouldn't be
available through the notification settings association as this will
throw an exception when we try to show the link.

CHANGELOG

@@ -17,6 +17,7 @@ v 8.10.0 (unreleased)
   - Fix MR-auto-close text added to description. !4836
   - Fix issue, preventing users w/o push access to sort tags !5105 (redetection)
   - Add Spring EmojiOne updates.
+  - Fix viewing notification settings when a project is pending deletion
   - Fix pagination when sorting by columns with lots of ties (like priority)
   - Updated project header design
   - Exclude email check from the standard health check

app/models/notification_setting.rb

@@ -5,6 +5,7 @@ class NotificationSetting < ActiveRecord::Base
 
   belongs_to :user
   belongs_to :source, polymorphic: true
+  belongs_to :project, foreign_key: 'source_id'
 
   validates :user, presence: true
   validates :level, presence: true
@@ -13,7 +14,13 @@ class NotificationSetting < ActiveRecord::Base
                                     allow_nil: true }
 
   scope :for_groups, -> { where(source_type: 'Namespace') }
-  scope :for_projects, -> { where(source_type: 'Project') }
+
+  # Exclude projects not included by the Project model's default scope (those that are
+  # pending delete).
+  #
+  scope :for_projects, -> do
+    includes(:project).references(:projects).where(source_type: 'Project').where.not(projects: { id: nil })
+  end
 
   EMAIL_EVENTS = [
     :new_note,

spec/factories/notification_settings.rb

+FactoryGirl.define do
+  factory :notification_setting do
+    source factory: :empty_project
+    user
+    level 3
+    events []
+  end
+end

spec/models/notification_setting_spec.rb

@@ -38,4 +38,21 @@ RSpec.describe NotificationSetting, type: :model do
       end
     end
   end
+
+  describe '#for_projects' do
+    let(:user) { create(:user) }
+
+    before do
+      1.upto(4) do |i|
+        setting = create(:notification_setting, user: user)
+
+        setting.project.update_attributes(pending_delete: true) if i.even?
+      end
+    end
+
+    it 'excludes projects pending delete' do
+      expect(user.notification_settings.for_projects).to all(have_attributes(project: an_instance_of(Project)))
+      expect(user.notification_settings.for_projects.map(&:project)).to all(have_attributes(pending_delete: false))
+    end
+  end
 end