Add total time spent to milestones

app/models/global_milestone.rb

@@ -152,4 +152,12 @@ class GlobalMilestone
         @milestones.first.start_date
       end
   end
+
+  def total_time_spent
+    issues.joins(:timelogs).sum(:time_spent) + merge_requests.joins(:timelogs).sum(:time_spent)
+  end
+
+  def human_total_time_spent
+    Gitlab::TimeTrackingFormatter.output(total_time_spent) || 0
+  end
 end

app/models/milestone.rb

@@ -213,6 +213,14 @@ class Milestone < ActiveRecord::Base
     project_id.present?
   end
 
+  def total_time_spent
+    issues.joins(:timelogs).sum(:time_spent) + merge_requests.joins(:timelogs).sum(:time_spent)
+  end
+
+  def human_total_time_spent
+    Gitlab::TimeTrackingFormatter.output(total_time_spent) || 0
+  end
+
   private
 
   # Milestone titles must be unique across project milestones and group milestones

app/views/shared/milestones/_sidebar.html.haml

@@ -85,6 +85,16 @@
               Closed:
               = milestone.issues_visible_to_user(current_user).closed.count
 
+    .block.time_spent
+      .sidebar-collapsed-icon
+        %strong
+          = custom_icon('icon_clock_o')
+        %span= milestone.human_total_time_spent
+      .title.hide-collapsed
+        Total time spent
+      .value.hide-collapsed
+        = milestone.human_total_time_spent
+
     .block.merge-requests
       .sidebar-collapsed-icon
         %strong

spec/models/global_milestone_spec.rb

@@ -190,4 +190,37 @@ describe GlobalMilestone do
       end
     end
   end
+
+  describe '#total_time_spent' do
+    let(:milestone1_project1) { create(:milestone, title: "Milestone v1.2", project: project1) }
+    let(:milestone1_project2) { create(:milestone, title: "Milestone v1.2", project: project2) }
+    let(:issue1) { create(:issue, milestone: milestone1_project1) }
+    let(:issue2) { create(:issue, milestone: milestone1_project2) }
+    let(:merge_request1) { create(:merge_request, milestone: milestone1_project1) }
+    let(:merge_request2) { create(:merge_request, milestone: milestone1_project2) }
+
+    before do
+      milestones =
+        [
+          milestone1_project1,
+          milestone1_project2
+        ]
+      milestones_relation = Milestone.where(id: milestones.map(&:id))
+
+      @global_milestone = described_class.new(milestone1_project1.title, milestones_relation)
+    end
+
+    it 'calculates total time spent' do
+      issue1.spend_time(duration: 300, user: user)
+      issue1.save!
+      issue2.spend_time(duration: 600, user: user2)
+      issue2.save!
+      merge_request1.spend_time(duration: 200, user: user)
+      merge_request1.save!
+      merge_request2.spend_time(duration: 100, user: user2)
+      merge_request2.save!
+
+      expect(@global_milestone.total_time_spent).to eq(1200)
+    end
+  end
 end

spec/models/milestone_spec.rb

@@ -284,4 +284,27 @@ describe Milestone do
       expect(milestone.participants).to eq [user]
     end
   end
+
+  describe '#total_time_spent' do
+    let(:user) { build(:user) }
+    let(:project) { build(:project, name: 'sample-project') }
+    let(:milestone) { build(:milestone, iid: 1, project: project) }
+    let(:issue1) { build(:issue, milestone: milestone) }
+    let(:issue2) { build(:issue, milestone: milestone) }
+    let(:merge_request1) { build(:merge_request, milestone: milestone) }
+    let(:merge_request2) { build(:merge_request, milestone: milestone) }
+
+    it 'calculates total time spent' do
+      issue1.spend_time(duration: 300, user: user)
+      issue1.save!
+      issue2.spend_time(duration: 600, user: user)
+      issue2.save!
+      merge_request1.spend_time(duration: 200, user: user)
+      merge_request1.save!
+      merge_request2.spend_time(duration: 100, user: user)
+      merge_request2.save!
+
+      expect(milestone.total_time_spent).to eq(1200)
+    end
+  end
 end