Move a user's award emoji to the ghost user

... when the user is destroyed.

1. Normally, for a given awardable and award emoji name, a user is only allowed
   to create a single award emoji.

2. This validation needs to be removed for ghost users, since:

   - User A and User B have created award emoji - with the same name and against
     the same awardable
   - User A is deleted. Their award emoji is moved to the ghost user
   - User B is deleted. Their award emoji needs to be moved to the ghost user.
     However, this breaks the uniqueness validation, since the ghost user is
     only allowed to have one award emoji of a given name for a given awardable

app/models/award_emoji.rb

@@ -3,13 +3,14 @@ class AwardEmoji < ActiveRecord::Base
   UPVOTE_NAME   = "thumbsup".freeze
   include Participable
+  include GhostUser
   belongs_to :awardable, polymorphic: true
   belongs_to :user
   validates :awardable, :user, presence: true
   validates :name, presence: true, inclusion: { in: Gitlab::Emoji.emojis_names }
-  validates :name, uniqueness: { scope: [:user, :awardable_type, :awardable_id] }
+  validates :name, uniqueness: { scope: [:user, :awardable_type, :awardable_id] }, unless: :ghost_user?
   participant :user

app/models/concerns/ghost_user.rb

+module GhostUser
+  extend ActiveSupport::Concern
+
+  def ghost_user?
+    user && user.ghost?
+  end
+end

app/services/concerns/users/migrate_to_ghost_user.rb

@@ -23,6 +23,7 @@ module Users::MigrateToGhostUser
       migrate_merge_requests(user)
       migrate_notes(user)
       migrate_abuse_reports(user)
+      migrate_award_emoji(user)
     end
     user.reload
@@ -45,4 +46,8 @@ module Users::MigrateToGhostUser
   def migrate_abuse_reports(user)
     AbuseReport.where(reporter_id: user.id).update_all(reporter_id: ghost_user.id)
   end
+
+  def migrate_award_emoji(user)
+    user.award_emoji.update_all(user_id: ghost_user.id)
+  end
 end

spec/models/award_emoji_spec.rb

@@ -25,6 +25,20 @@ describe AwardEmoji, models: true do
         expect(new_award).not_to be_valid
       end
+
+      # Assume User A and User B both created award emoji of the same name
+      # on the same awardable. When User A is deleted, User A's award emoji
+      # is moved to the ghost user. When User B is deleted, User B's award emoji
+      # also needs to be moved to the ghost user - this cannot happen unless
+      # the uniqueness validation is disabled for ghost users.
+      it "allows duplicate award emoji for ghost users" do
+        user  = create(:user, :ghost)
+        issue = create(:issue)
+        create(:award_emoji, user: user, awardable: issue)
+        new_award = build(:award_emoji, user: user, awardable: issue)
+
+        expect(new_award).to be_valid
+      end
     end
   end
 end

spec/services/users/destroy_service_spec.rb

@@ -166,7 +166,35 @@ describe Users::DestroyService, services: true do
       context 'abuse reports' do
         include_examples "migrating a deleted user's associated records to the ghost user", AbuseReport, { skip_assignee_specs: true } do
           let(:created_record) { create(:abuse_report, reporter: user, user: create(:user)) }
-          let(:author_method) { :reporter }
+        end
+      end
+
+      context 'award emoji' do
+        include_examples "migrating a deleted user's associated records to the ghost user", AwardEmoji, { skip_assignee_specs: true } do
+          let(:created_record) { create(:award_emoji, user: user) }
+          let(:author_alias) { :user }
+
+          context "when the awardable already has an award emoji of the same name assigned to the ghost user" do
+            let(:awardable) { create(:issue) }
+            let!(:existing_award_emoji) { create(:award_emoji, user: User.ghost, name: "thumbsup", awardable: awardable) }
+            let!(:award_emoji) { create(:award_emoji, user: user, name: "thumbsup", awardable: awardable) }
+
+            it "migrates the award emoji regardless" do
+              service.execute(user)
+
+              migrated_record = AwardEmoji.find_by_id(award_emoji.id)
+
+              expect(migrated_record.user).to eq(User.ghost)
+            end
+
+            it "does not leave the migrated award emoji in an invalid state" do
+              service.execute(user)
+
+              migrated_record = AwardEmoji.find_by_id(award_emoji.id)
+
+              expect(migrated_record).to be_valid
+            end
+          end
         end
       end
     end

spec/support/services/user_destroy_service_migrate_to_ghost_user_shared_examples.rb

@@ -23,7 +23,11 @@ shared_examples "migrating a deleted user's associated records to the ghost user
       migrated_record = record_class.find_by_id(record.id)
-      expect(migrated_record.author).to eq(User.ghost)
+      if migrated_record.respond_to?(:author)
+        expect(migrated_record.author).to eq(User.ghost)
+      else
+        expect(migrated_record.send(author_alias)).to eq(User.ghost)
+      end
     end
     it "blocks the user before migrating #{record_class_name}s to the 'Ghost User'" do