Introduce new service to handle add_spent_time for MRs

This new service creates a timelog from the given duration, creates a
system note, tracks usage and calls the merge request webhooks.

When the :use_specialized_service parameter gets used we'll be able to
call this service to avoid updating the whole merge request just to get
the spent time added.

Changelog: performance

app/services/merge_requests/add_spent_time_service.rb

+# frozen_string_literal: true
+
+module MergeRequests
+  class AddSpentTimeService < UpdateService
+    def execute(merge_request)
+      old_associations = { total_time_spent: merge_request.total_time_spent }
+
+      merge_request.spend_time(params[:spend_time])
+
+      merge_request_saved = merge_request.with_transaction_returning_status do
+        merge_request.save
+      end
+
+      if merge_request_saved
+        create_system_notes(merge_request)
+
+        # track usage
+        track_time_spend_edits(merge_request, old_associations[:total_time_spent])
+
+        execute_hooks(merge_request, 'update', old_associations: old_associations)
+      end
+
+      merge_request
+    end
+
+    private
+
+    def track_time_spend_edits(merge_request, old_total_time_spent)
+      if old_total_time_spent != merge_request.total_time_spent
+        merge_request_activity_counter.track_time_spent_changed_action(user: current_user)
+      end
+    end
+  end
+end

app/services/merge_requests/update_service.rb

@@ -295,6 +295,8 @@ module MergeRequests
       case attribute
       when :assignee_ids
         assignees_service.execute(merge_request)
+      when :spend_time
+        add_time_spent_service.execute(merge_request)
       else
         nil
       end
@@ -304,6 +306,10 @@ module MergeRequests
       @assignees_service ||= ::MergeRequests::UpdateAssigneesService
         .new(project, current_user, params)
     end
+
+    def add_time_spent_service
+      @add_time_spent_service ||= ::MergeRequests::AddSpentTimeService.new(project, current_user, params)
+    end
   end
 end
 

spec/services/merge_requests/add_spent_time_service_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe MergeRequests::AddSpentTimeService do
+  let_it_be(:user) { create(:user) }
+  let_it_be(:project) { create(:project, :public, :repository) }
+  let_it_be_with_reload(:merge_request) { create(:merge_request, :simple, :unique_branches, source_project: project) }
+
+  let(:duration) { 1500 }
+  let(:params) { { spend_time: { duration: duration, user_id: user.id } } }
+  let(:service) { described_class.new(project, user, params) }
+
+  describe '#execute' do
+    before do
+      project.add_developer(user)
+    end
+
+    it 'creates a new timelog with the specified duration' do
+      expect { service.execute(merge_request) }.to change { Timelog.count }.from(0).to(1)
+
+      timelog = merge_request.timelogs.last
+
+      expect(timelog).not_to be_nil
+      expect(timelog.time_spent).to eq(1500)
+    end
+
+    it 'creates a system note with the time added' do
+      expect { service.execute(merge_request) }.to change { Note.count }.from(0).to(1)
+
+      system_note = merge_request.notes.last
+
+      expect(system_note).not_to be_nil
+      expect(system_note.note_html).to include('added 25m of time spent')
+    end
+
+    it 'saves usage data' do
+      expect(Gitlab::UsageDataCounters::MergeRequestActivityUniqueCounter)
+        .to receive(:track_time_spent_changed_action).once.with(user: user)
+
+      service.execute(merge_request)
+    end
+
+    it 'is more efficient than using the full update-service' do
+      other_mr = create(:merge_request, :simple, :unique_branches, source_project: project)
+
+      update_service = ::MergeRequests::UpdateService.new(project, user, params)
+      other_mr.reload
+
+      expect { service.execute(merge_request) }
+        .to issue_fewer_queries_than { update_service.execute(other_mr) }
+    end
+
+    context 'when duration is nil' do
+      let(:duration) { nil }
+
+      it 'does not create a timelog with the specified duration' do
+        expect { service.execute(merge_request) }.not_to change { Timelog.count }
+        expect(merge_request).not_to be_valid
+      end
+    end
+  end
+end

spec/services/merge_requests/update_service_spec.rb

@@ -1052,6 +1052,51 @@ RSpec.describe MergeRequests::UpdateService, :mailer do
       end
     end
 
+    context 'when adding time spent' do
+      context ':use_specialized_service' do
+        context 'when true' do
+          it 'passes the update action to ::MergeRequests::AddSpentTimeService' do
+            expect(::MergeRequests::AddSpentTimeService)
+              .to receive(:new).and_call_original
+
+            update_merge_request({
+              spend_time: {
+                duration: 1800, # 30min
+                user_id: user3.id
+              },
+              use_specialized_service: true
+            })
+          end
+        end
+
+        context 'when false or nil' do
+          before do
+            expect(::MergeRequests::AddSpentTimeService).not_to receive(:new)
+          end
+
+          it 'does not pass the update action to ::MergeRequests::UpdateAssigneesService when false' do
+            update_merge_request({
+              spend_time: {
+                duration: 1800, # 30min
+                user_id: user3.id
+              },
+              use_specialized_service: false
+            })
+          end
+
+          it 'does not pass the update action to ::MergeRequests::UpdateAssigneesService when nil' do
+            update_merge_request({
+              spend_time: {
+                duration: 1800, # 30min
+                user_id: user3.id
+              },
+              use_specialized_service: nil
+            })
+          end
+        end
+      end
+    end
+
     include_examples 'issuable update service' do
       let(:open_issuable) { merge_request }
       let(:closed_issuable) { create(:closed_merge_request, source_project: project) }