Return last edited time instead of update time

For issuable models we keep two timestamps:
updated_at which is updated whenever any model attribute is changed,
last_edited_at which is changed when only title or description is
changed.

In UI bellow description we display who and when updated the item. But
last_edited_by (used for 'who') is mistakenly combined with updated_at
(when), last_edited_at should be used instead.

Closes #41247

app/controllers/concerns/issuable_actions.rb

@@ -45,7 +45,7 @@ module IssuableActions
     }
 
     if issuable.edited?
-      response[:updated_at] = issuable.updated_at
+      response[:updated_at] = issuable.last_edited_at.to_time.iso8601
       response[:updated_by_name] = issuable.last_edited_by.name
       response[:updated_by_path] = user_path(issuable.last_edited_by)
     end

app/helpers/issuables_helper.rb

@@ -241,7 +241,7 @@ module IssuablesHelper
     return {} unless issuable.edited?
 
     {
-      updatedAt: issuable.updated_at.to_time.iso8601,
+      updatedAt: issuable.last_edited_at.to_time.iso8601,
       updatedBy: {
         name: issuable.last_edited_by.name,
         path: user_path(issuable.last_edited_by)

changelogs/unreleased/41247-timestamp.yml

+---
+title: For issues display time of last edit of title or description instead of time
+  of any attribute change
+merge_request:
+author:
+type: fixed

spec/controllers/projects/issues_controller_spec.rb

@@ -301,6 +301,53 @@ describe Projects::IssuesController do
     end
   end
 
+  describe 'GET #realtime_changes' do
+    def go(id:)
+      get :realtime_changes,
+        namespace_id: project.namespace.to_param,
+        project_id: project,
+        id: id
+    end
+
+    context 'when an issue was edited' do
+      before do
+        project.add_developer(user)
+
+        issue.update!(last_edited_by: user, last_edited_at: issue.created_at + 1.minute)
+
+        sign_in(user)
+      end
+
+      it 'returns last edited time' do
+        go(id: issue.iid)
+
+        data = JSON.parse(response.body)
+
+        expect(data).to include('updated_at')
+        expect(data['updated_at']).to eq(issue.last_edited_at.to_time.iso8601)
+      end
+    end
+
+    context 'when an issue was edited by a deleted user' do
+      let(:deleted_user) { create(:user) }
+
+      before do
+        project.add_developer(user)
+
+        issue.update!(last_edited_by: deleted_user, last_edited_at: Time.now)
+
+        deleted_user.destroy
+        sign_in(user)
+      end
+
+      it 'returns 200' do
+        go(id: issue.iid)
+
+        expect(response).to have_gitlab_http_status(200)
+      end
+    end
+  end
+
   describe 'Confidential Issues' do
     let(:project) { create(:project_empty_repo, :public) }
     let(:assignee) { create(:assignee) }
@@ -589,25 +636,6 @@ describe Projects::IssuesController do
           project_id: project,
           id: id
       end
-
-      context 'when an issue was edited by a deleted user' do
-        let(:deleted_user) { create(:user) }
-
-        before do
-          project.add_developer(user)
-
-          issue.update!(last_edited_by: deleted_user, last_edited_at: Time.now)
-
-          deleted_user.destroy
-          sign_in(user)
-        end
-
-        it 'returns 200' do
-          go(id: issue.iid)
-
-          expect(response).to have_gitlab_http_status(200)
-        end
-      end
     end
 
     describe 'GET #edit' do

spec/helpers/issuables_helper_spec.rb

@@ -125,10 +125,10 @@ describe IssuablesHelper do
   describe '#updated_at_by' do
     let(:user) { create(:user) }
     let(:unedited_issuable) { create(:issue) }
-    let(:edited_issuable) { create(:issue, last_edited_by: user, created_at: 3.days.ago, updated_at: 2.days.ago, last_edited_at: 2.days.ago) }
+    let(:edited_issuable) { create(:issue, last_edited_by: user, created_at: 3.days.ago, updated_at: 1.day.ago, last_edited_at: 2.days.ago) }
     let(:edited_updated_at_by) do
       {
-        updatedAt: edited_issuable.updated_at.to_time.iso8601,
+        updatedAt: edited_issuable.last_edited_at.to_time.iso8601,
         updatedBy: {
           name: user.name,
           path: user_path(user)
@@ -142,7 +142,7 @@ describe IssuablesHelper do
     context 'when updated by a deleted user' do
       let(:edited_updated_at_by) do
         {
-          updatedAt: edited_issuable.updated_at.to_time.iso8601,
+          updatedAt: edited_issuable.last_edited_at.to_time.iso8601,
           updatedBy: {
             name: User.ghost.name,
             path: user_path(User.ghost)