Removes legacy GlobalLabel class

Removes the last usage of GlobalLabel. This changes the dashboard labels
endpoint to get a unique list of label titles using SQL.

GlobalLabel used to be how we implemented group labels where we grouped
project labels by title. For this dashboard endpoint, we're not showing
group labels but we're only returning labels that have unique titles
because these are used by the filter bar and we filter by title so
duplicates are redundant.

app/controllers/dashboard/labels_controller.rb

@@ -11,8 +11,8 @@ class Dashboard::LabelsController < Dashboard::ApplicationController
 
   def labels
     finder_params = { project_ids: projects.select(:id) }
-    labels = LabelsFinder.new(current_user, finder_params).execute
 
-    GlobalLabel.build_collection(labels)
+    LabelsFinder.new(current_user, finder_params).execute
+      .select('DISTINCT ON (labels.title) labels.*')
   end
 end

app/models/global_label.rb

-# frozen_string_literal: true
-
-class GlobalLabel
-  include Presentable
-
-  attr_accessor :title, :labels
-  alias_attribute :name, :title
-
-  delegate :color, :text_color, :description, :scoped_label?, to: :@first_label
-
-  def for_display
-    @first_label
-  end
-
-  def self.build_collection(labels)
-    labels = labels.group_by(&:title)
-
-    labels.map do |title, labels|
-      new(title, labels)
-    end
-  end
-
-  def initialize(title, labels)
-    @title = title
-    @labels = labels
-    @first_label = labels.find { |lbl| lbl.description.present? } || labels.first
-  end
-
-  def present(attributes)
-    super(attributes.merge(presenter_class: ::LabelPresenter))
-  end
-end

app/serializers/label_entity.rb

 # frozen_string_literal: true
 
 class LabelEntity < Grape::Entity
-  expose :id, if: ->(label, _) { !label.is_a?(GlobalLabel) }
+  expose :id
 
   expose :title
   expose :color
   expose :description
   expose :group_id
-  expose :project_id, if: ->(label, _) { !label.is_a?(GlobalLabel) }
+  expose :project_id
   expose :template
   expose :text_color
   expose :created_at

spec/controllers/dashboard/labels_controller_spec.rb

@@ -3,27 +3,32 @@
 require 'spec_helper'
 
 RSpec.describe Dashboard::LabelsController do
-  let(:project) { create(:project) }
-  let(:user)    { create(:user) }
-  let!(:label)  { create(:label, project: project) }
+  let_it_be(:user) { create(:user) }
+  let_it_be(:project) { create(:project) }
+  let_it_be(:project_2) { create(:project) }
+
+  let_it_be(:label) { create(:label, project: project, title: 'some_label') }
+  let_it_be(:label_with_same_title) { create(:label, project: project_2, title: 'some_label') }
+  let_it_be(:unrelated_label) { create(:label, project: create(:project, :public)) }
+
+  before_all do
+    project.add_reporter(user)
+    project_2.add_reporter(user)
+  end
 
   before do
     sign_in(user)
-    project.add_reporter(user)
   end
 
   describe "#index" do
-    let!(:unrelated_label) { create(:label, project: create(:project, :public)) }
-
     subject { get :index, format: :json }
 
-    it 'returns global labels for projects the user has a relationship with' do
+    it 'returns labels with unique titles for projects the user has a relationship with' do
       subject
 
       expect(json_response).to be_kind_of(Array)
       expect(json_response.size).to eq(1)
-      expect(json_response[0]["id"]).to be_nil
-      expect(json_response[0]["title"]).to eq(label.title)
+      expect(json_response[0]['title']).to eq(label.title)
     end
 
     it_behaves_like 'disabled when using an external authorization service'