Use ResourceLabelEvent for tracking label changes

26 files changed, 574 insertions, 91 deletions

diff --git a/spec/controllers/projects/notes_controller_spec.rb b/spec/controllers/projects/notes_controller_spec.rb
index 1458113b90c..81badaac76b 100644
--- a/spec/controllers/projects/notes_controller_spec.rb
+++ b/spec/controllers/projects/notes_controller_spec.rb
@@ -154,7 +154,7 @@ describe Projects::NotesController do
         get :index, request_params
 
         expect(parsed_response[:notes].count).to eq(1)
-        expect(note_json[:id]).to eq(note.id)
+        expect(note_json[:id]).to eq(note.id.to_s)
       end
 
       it 'does not result in N+1 queries' do
diff --git a/spec/factories/resource_label_events.rb b/spec/factories/resource_label_events.rb
index a67ad78c098..739ba901052 100644
--- a/spec/factories/resource_label_events.rb
+++ b/spec/factories/resource_label_events.rb
@@ -2,9 +2,12 @@
 
 FactoryBot.define do
   factory :resource_label_event do
-    user { issue.project.creator }
     action :add
     label
-    issue
+    user { issuable&.author || create(:user) }
+
+    after(:build) do |event, evaluator|
+      event.issue = create(:issue) unless event.issuable
+    end
   end
 end
diff --git a/spec/features/issues/resource_label_events_spec.rb b/spec/features/issues/resource_label_events_spec.rb
new file mode 100644
index 00000000000..40c452c991a
--- /dev/null
+++ b/spec/features/issues/resource_label_events_spec.rb
@@ -0,0 +1,60 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+describe 'List issue resource label events', :js do
+  let(:user)     { create(:user) }
+  let(:project)  { create(:project, :public) }
+  let(:issue)    { create(:issue, project: project, author: user) }
+  let!(:label)    { create(:label, project: project, title: 'foo') }
+
+  context 'when user displays the issue' do
+    let!(:note)     { create(:note_on_issue, author: user, project: project, noteable: issue, note: 'some note') }
+    let!(:event)    { create(:resource_label_event, user: user, issue: issue, label: label) }
+
+    before do
+      visit project_issue_path(project, issue)
+      wait_for_requests
+    end
+
+    it 'shows both notes and resource label events' do
+      page.within('#notes') do
+        expect(find("#note_#{note.id}")).to have_content 'some note'
+        expect(find("#note_#{event.discussion_id}")).to have_content 'added foo label'
+      end
+    end
+  end
+
+  context 'when user adds label to the issue' do
+    def toggle_labels(labels)
+      page.within '.labels' do
+        click_link 'Edit'
+        wait_for_requests
+
+        labels.each { |label| click_link label }
+
+        click_link 'Edit'
+        wait_for_requests
+      end
+    end
+
+    before do
+      create(:label, project: project, title: 'bar')
+      project.add_developer(user)
+
+      sign_in(user)
+      visit project_issue_path(project, issue)
+      wait_for_requests
+    end
+
+    it 'shows add note for newly added labels' do
+      toggle_labels(%w(foo bar))
+      visit project_issue_path(project, issue)
+      wait_for_requests
+
+      page.within('#notes') do
+        expect(page).to have_content 'added bar foo labels'
+      end
+    end
+  end
+end
diff --git a/spec/javascripts/diffs/mock_data/diff_discussions.js b/spec/javascripts/diffs/mock_data/diff_discussions.js
index 41d0dfd8939..b29a22da7c2 100644
--- a/spec/javascripts/diffs/mock_data/diff_discussions.js
+++ b/spec/javascripts/diffs/mock_data/diff_discussions.js
@@ -16,7 +16,7 @@ export default {
   expanded: true,
   notes: [
     {
-      id: 1749,
+      id: '1749',
       type: 'DiffNote',
       attachment: null,
       author: {
@@ -68,7 +68,7 @@ export default {
         '/gitlab-org/gitlab-test/issues/new?discussion_to_resolve=6b232e05bea388c6b043ccc243ba505faac04ea8&merge_request_to_resolve_discussions_of=20',
     },
     {
-      id: 1753,
+      id: '1753',
       type: 'DiffNote',
       attachment: null,
       author: {
@@ -120,7 +120,7 @@ export default {
         '/gitlab-org/gitlab-test/issues/new?discussion_to_resolve=6b232e05bea388c6b043ccc243ba505faac04ea8&merge_request_to_resolve_discussions_of=20',
     },
     {
-      id: 1754,
+      id: '1754',
       type: 'DiffNote',
       attachment: null,
       author: {
@@ -162,7 +162,7 @@ export default {
         '/gitlab-org/gitlab-test/issues/new?discussion_to_resolve=6b232e05bea388c6b043ccc243ba505faac04ea8&merge_request_to_resolve_discussions_of=20',
     },
     {
-      id: 1755,
+      id: '1755',
       type: 'DiffNote',
       attachment: null,
       author: {
@@ -204,7 +204,7 @@ export default {
         '/gitlab-org/gitlab-test/issues/new?discussion_to_resolve=6b232e05bea388c6b043ccc243ba505faac04ea8&merge_request_to_resolve_discussions_of=20',
     },
     {
-      id: 1756,
+      id: '1756',
       type: 'DiffNote',
       attachment: null,
       author: {
diff --git a/spec/javascripts/notes/components/note_actions_spec.js b/spec/javascripts/notes/components/note_actions_spec.js
index 52cc42cb53d..d7298cb3483 100644
--- a/spec/javascripts/notes/components/note_actions_spec.js
+++ b/spec/javascripts/notes/components/note_actions_spec.js
@@ -28,7 +28,7 @@ describe('issue_note_actions component', () => {
         canEdit: true,
         canAwardEmoji: true,
         canReportAsAbuse: true,
-        noteId: 539,
+        noteId: '539',
         noteUrl: 'https://localhost:3000/group/project/merge_requests/1#note_1',
         reportAbusePath:
           '/abuse_reports/new?ref_url=http%3A%2F%2Flocalhost%3A3000%2Fgitlab-org%2Fgitlab-ce%2Fissues%2F7%23note_539&user_id=26',
@@ -59,6 +59,20 @@ describe('issue_note_actions component', () => {
         expect(vm.$el.querySelector(`a[href="${props.reportAbusePath}"]`)).toBeDefined();
       });
 
+      it('should be possible to copy link to a note', () => {
+        expect(vm.$el.querySelector('.js-btn-copy-note-link')).not.toBeNull();
+      });
+
+      it('should not show copy link action when `noteUrl` prop is empty', done => {
+        vm.noteUrl = '';
+        Vue.nextTick()
+          .then(() => {
+            expect(vm.$el.querySelector('.js-btn-copy-note-link')).toBeNull();
+          })
+          .then(done)
+          .catch(done.fail);
+      });
+
       it('should be possible to delete comment', () => {
         expect(vm.$el.querySelector('.js-note-delete')).toBeDefined();
       });
@@ -77,7 +91,7 @@ describe('issue_note_actions component', () => {
         canEdit: false,
         canAwardEmoji: false,
         canReportAsAbuse: false,
-        noteId: 539,
+        noteId: '539',
         noteUrl: 'https://localhost:3000/group/project/merge_requests/1#note_1',
         reportAbusePath:
           '/abuse_reports/new?ref_url=http%3A%2F%2Flocalhost%3A3000%2Fgitlab-org%2Fgitlab-ce%2Fissues%2F7%23note_539&user_id=26',
diff --git a/spec/javascripts/notes/components/note_awards_list_spec.js b/spec/javascripts/notes/components/note_awards_list_spec.js
index 9d98ba219da..6a6a810acff 100644
--- a/spec/javascripts/notes/components/note_awards_list_spec.js
+++ b/spec/javascripts/notes/components/note_awards_list_spec.js
@@ -30,7 +30,7 @@ describe('note_awards_list component', () => {
       propsData: {
         awards: awardsMock,
         noteAuthorId: 2,
-        noteId: 545,
+        noteId: '545',
         canAwardEmoji: true,
         toggleAwardPath: '/gitlab-org/gitlab-ce/notes/545/toggle_award_emoji',
       },
@@ -70,7 +70,7 @@ describe('note_awards_list component', () => {
         propsData: {
           awards: awardsMock,
           noteAuthorId: 2,
-          noteId: 545,
+          noteId: '545',
           canAwardEmoji: false,
           toggleAwardPath: '/gitlab-org/gitlab-ce/notes/545/toggle_award_emoji',
         },
diff --git a/spec/javascripts/notes/components/note_form_spec.js b/spec/javascripts/notes/components/note_form_spec.js
index 95d400ab3df..147ffcf1b81 100644
--- a/spec/javascripts/notes/components/note_form_spec.js
+++ b/spec/javascripts/notes/components/note_form_spec.js
@@ -19,7 +19,7 @@ describe('issue_note_form component', () => {
     props = {
       isEditing: false,
       noteBody: 'Magni suscipit eius consectetur enim et ex et commodi.',
-      noteId: 545,
+      noteId: '545',
     };
 
     vm = new Component({
@@ -32,6 +32,22 @@ describe('issue_note_form component', () => {
     vm.$destroy();
   });
 
+  describe('noteHash', () => {
+    it('returns note hash string based on `noteId`', () => {
+      expect(vm.noteHash).toBe(`#note_${props.noteId}`);
+    });
+
+    it('return note hash as `#` when `noteId` is empty', done => {
+      vm.noteId = '';
+      Vue.nextTick()
+        .then(() => {
+          expect(vm.noteHash).toBe('#');
+        })
+        .then(done)
+        .catch(done.fail);
+    });
+  });
+
   describe('conflicts editing', () => {
     it('should show conflict message if note changes outside the component', done => {
       vm.isEditing = true;
diff --git a/spec/javascripts/notes/components/note_header_spec.js b/spec/javascripts/notes/components/note_header_spec.js
index a3c6bf78988..379780f43a0 100644
--- a/spec/javascripts/notes/components/note_header_spec.js
+++ b/spec/javascripts/notes/components/note_header_spec.js
@@ -33,7 +33,7 @@ describe('note_header component', () => {
           },
           createdAt: '2017-08-02T10:51:58.559Z',
           includeToggle: false,
-          noteId: 1394,
+          noteId: '1394',
           expanded: true,
         },
       }).$mount();
@@ -47,6 +47,16 @@ describe('note_header component', () => {
     it('should render timestamp link', () => {
       expect(vm.$el.querySelector('a[href="#note_1394"]')).toBeDefined();
     });
+
+    it('should not render user information when prop `author` is empty object', done => {
+      vm.author = {};
+      Vue.nextTick()
+        .then(() => {
+          expect(vm.$el.querySelector('.note-header-author-name')).toBeNull();
+        })
+        .then(done)
+        .catch(done.fail);
+    });
   });
 
   describe('discussion', () => {
@@ -66,7 +76,7 @@ describe('note_header component', () => {
           },
           createdAt: '2017-08-02T10:51:58.559Z',
           includeToggle: true,
-          noteId: 1395,
+          noteId: '1395',
           expanded: true,
         },
       }).$mount();
diff --git a/spec/javascripts/notes/mock_data.js b/spec/javascripts/notes/mock_data.js
index 0423fcb6ec4..1f030e5af28 100644
--- a/spec/javascripts/notes/mock_data.js
+++ b/spec/javascripts/notes/mock_data.js
@@ -66,7 +66,7 @@ export const individualNote = {
   individual_note: true,
   notes: [
     {
-      id: 1390,
+      id: '1390',
       attachment: {
         url: null,
         filename: null,
@@ -111,7 +111,7 @@ export const individualNote = {
 };
 
 export const note = {
-  id: 546,
+  id: '546',
   attachment: {
     url: null,
     filename: null,
@@ -174,7 +174,7 @@ export const discussionMock = {
   expanded: true,
   notes: [
     {
-      id: 1395,
+      id: '1395',
       attachment: {
         url: null,
         filename: null,
@@ -211,7 +211,7 @@ export const discussionMock = {
       path: '/gitlab-org/gitlab-ce/notes/1395',
     },
     {
-      id: 1396,
+      id: '1396',
       attachment: {
         url: null,
         filename: null,
@@ -257,7 +257,7 @@ export const discussionMock = {
       path: '/gitlab-org/gitlab-ce/notes/1396',
     },
     {
-      id: 1437,
+      id: '1437',
       attachment: {
         url: null,
         filename: null,
@@ -308,7 +308,7 @@ export const discussionMock = {
 };
 
 export const loggedOutnoteableData = {
-  id: 98,
+  id: '98',
   iid: 26,
   author_id: 1,
   description: '',
@@ -358,7 +358,7 @@ export const collapseNotesMock = [
     individual_note: true,
     notes: [
       {
-        id: 1390,
+        id: '1390',
         attachment: null,
         author: {
           id: 1,
@@ -393,7 +393,7 @@ export const collapseNotesMock = [
     individual_note: true,
     notes: [
       {
-        id: 1391,
+        id: '1391',
         attachment: null,
         author: {
           id: 1,
@@ -433,7 +433,7 @@ export const INDIVIDUAL_NOTE_RESPONSE_MAP = {
         expanded: true,
         notes: [
           {
-            id: 1390,
+            id: '1390',
             attachment: {
               url: null,
               filename: null,
@@ -495,7 +495,7 @@ export const INDIVIDUAL_NOTE_RESPONSE_MAP = {
         expanded: true,
         notes: [
           {
-            id: 1391,
+            id: '1391',
             attachment: {
               url: null,
               filename: null,
@@ -544,7 +544,7 @@ export const INDIVIDUAL_NOTE_RESPONSE_MAP = {
     '/gitlab-org/gitlab-ce/notes/1471': {
       commands_changes: null,
       valid: true,
-      id: 1471,
+      id: '1471',
       attachment: null,
       author: {
         id: 1,
@@ -600,7 +600,7 @@ export const DISCUSSION_NOTE_RESPONSE_MAP = {
         expanded: true,
         notes: [
           {
-            id: 1471,
+            id: '1471',
             attachment: {
               url: null,
               filename: null,
@@ -671,7 +671,7 @@ export const notesWithDescriptionChanges = [
     expanded: true,
     notes: [
       {
-        id: 901,
+        id: '901',
         type: null,
         attachment: null,
         author: {
@@ -718,7 +718,7 @@ export const notesWithDescriptionChanges = [
     expanded: true,
     notes: [
       {
-        id: 902,
+        id: '902',
         type: null,
         attachment: null,
         author: {
@@ -765,7 +765,7 @@ export const notesWithDescriptionChanges = [
     expanded: true,
     notes: [
       {
-        id: 903,
+        id: '903',
         type: null,
         attachment: null,
         author: {
@@ -809,7 +809,7 @@ export const notesWithDescriptionChanges = [
     expanded: true,
     notes: [
       {
-        id: 904,
+        id: '904',
         type: null,
         attachment: null,
         author: {
@@ -854,7 +854,7 @@ export const notesWithDescriptionChanges = [
     expanded: true,
     notes: [
       {
-        id: 905,
+        id: '905',
         type: null,
         attachment: null,
         author: {
@@ -898,7 +898,7 @@ export const notesWithDescriptionChanges = [
     expanded: true,
     notes: [
       {
-        id: 906,
+        id: '906',
         type: null,
         attachment: null,
         author: {
@@ -945,7 +945,7 @@ export const collapsedSystemNotes = [
     expanded: true,
     notes: [
       {
-        id: 901,
+        id: '901',
         type: null,
         attachment: null,
         author: {
@@ -992,7 +992,7 @@ export const collapsedSystemNotes = [
     expanded: true,
     notes: [
       {
-        id: 902,
+        id: '902',
         type: null,
         attachment: null,
         author: {
@@ -1039,7 +1039,7 @@ export const collapsedSystemNotes = [
     expanded: true,
     notes: [
       {
-        id: 904,
+        id: '904',
         type: null,
         attachment: null,
         author: {
@@ -1084,7 +1084,7 @@ export const collapsedSystemNotes = [
     expanded: true,
     notes: [
       {
-        id: 905,
+        id: '905',
         type: null,
         attachment: null,
         author: {
@@ -1129,7 +1129,7 @@ export const collapsedSystemNotes = [
     expanded: true,
     notes: [
       {
-        id: 906,
+        id: '906',
         type: null,
         attachment: null,
         author: {
diff --git a/spec/javascripts/vue_shared/components/notes/system_note_spec.js b/spec/javascripts/vue_shared/components/notes/system_note_spec.js
index 2a6015fe35f..adcb1c858aa 100644
--- a/spec/javascripts/vue_shared/components/notes/system_note_spec.js
+++ b/spec/javascripts/vue_shared/components/notes/system_note_spec.js
@@ -9,7 +9,7 @@ describe('system note component', () => {
   beforeEach(() => {
     props = {
       note: {
-        id: 1424,
+        id: '1424',
         author: {
           id: 1,
           name: 'Root',
diff --git a/spec/lib/gitlab/import_export/all_models.yml b/spec/lib/gitlab/import_export/all_models.yml
index 2412cc3010a..ec2bdbe22e1 100644
--- a/spec/lib/gitlab/import_export/all_models.yml
+++ b/spec/lib/gitlab/import_export/all_models.yml
@@ -324,3 +324,9 @@ metrics:
 - latest_closed_by
 - merged_by
 - pipeline
+resource_label_events:
+- user
+- issue
+- merge_request
+- epic
+- label
diff --git a/spec/lib/gitlab/import_export/project.json b/spec/lib/gitlab/import_export/project.json
index 1b7fa11cb3c..eefd00e7383 100644
--- a/spec/lib/gitlab/import_export/project.json
+++ b/spec/lib/gitlab/import_export/project.json
@@ -331,6 +331,28 @@
           },
           "events": []
         }
+      ],
+      "resource_label_events": [
+        {
+          "id":244,
+          "action":"remove",
+          "issue_id":40,
+          "merge_request_id":null,
+          "label_id":2,
+          "user_id":1,
+          "created_at":"2018-08-28T08:24:00.494Z",
+          "label": {
+            "id": 2,
+            "title": "test2",
+            "color": "#428bca",
+            "project_id": 8,
+            "created_at": "2016-07-22T08:55:44.161Z",
+            "updated_at": "2016-07-22T08:55:44.161Z",
+            "template": false,
+            "description": "",
+            "type": "ProjectLabel"
+          }
+        }
       ]
     },
     {
@@ -2515,6 +2537,17 @@
           "events": []
         }
       ],
+      "resource_label_events": [
+        {
+          "id":243,
+          "action":"add",
+          "issue_id":null,
+          "merge_request_id":27,
+          "label_id":null,
+          "user_id":1,
+          "created_at":"2018-08-28T08:24:00.494Z"
+        }
+      ],
       "merge_request_diff": {
         "id": 27,
         "state": "collected",
diff --git a/spec/lib/gitlab/import_export/project_tree_restorer_spec.rb b/spec/lib/gitlab/import_export/project_tree_restorer_spec.rb
index a88ac0a091e..3ff6be595a8 100644
--- a/spec/lib/gitlab/import_export/project_tree_restorer_spec.rb
+++ b/spec/lib/gitlab/import_export/project_tree_restorer_spec.rb
@@ -89,6 +89,14 @@ describe Gitlab::ImportExport::ProjectTreeRestorer do
         expect(ProtectedTag.first.create_access_levels).not_to be_empty
       end
 
+      it 'restores issue resource label events' do
+        expect(Issue.find_by(title: 'Voluptatem').resource_label_events).not_to be_empty
+      end
+
+      it 'restores merge requests resource label events' do
+        expect(MergeRequest.find_by(title: 'MR1').resource_label_events).not_to be_empty
+      end
+
       context 'event at forth level of the tree' do
         let(:event) { Event.where(action: 6).first }
 
diff --git a/spec/lib/gitlab/import_export/project_tree_saver_spec.rb b/spec/lib/gitlab/import_export/project_tree_saver_spec.rb
index fec8a2af9ab..5dc372263ad 100644
--- a/spec/lib/gitlab/import_export/project_tree_saver_spec.rb
+++ b/spec/lib/gitlab/import_export/project_tree_saver_spec.rb
@@ -169,6 +169,14 @@ describe Gitlab::ImportExport::ProjectTreeSaver do
         expect(priorities.flatten).not_to be_empty
       end
 
+      it 'has issue resource label events' do
+        expect(saved_project_json['issues'].first['resource_label_events']).not_to be_empty
+      end
+
+      it 'has merge request resource label events' do
+        expect(saved_project_json['merge_requests'].first['resource_label_events']).not_to be_empty
+      end
+
       it 'saves the correct service type' do
         expect(saved_project_json['services'].first['type']).to eq('CustomIssueTrackerService')
       end
@@ -291,6 +299,9 @@ describe Gitlab::ImportExport::ProjectTreeSaver do
            project: project,
            commit_id: ci_build.pipeline.sha)
 
+    create(:resource_label_event, label: project_label, issue: issue)
+    create(:resource_label_event, label: group_label, merge_request: merge_request)
+
     create(:event, :created, target: milestone, project: project, author: user)
     create(:service, project: project, type: 'CustomIssueTrackerService', category: 'issue_tracker', properties: { one: 'value' })
 
diff --git a/spec/lib/gitlab/import_export/safe_model_attributes.yml b/spec/lib/gitlab/import_export/safe_model_attributes.yml
index 1be448b0486..e9f1be172b0 100644
--- a/spec/lib/gitlab/import_export/safe_model_attributes.yml
+++ b/spec/lib/gitlab/import_export/safe_model_attributes.yml
@@ -579,3 +579,11 @@ Badge:
 - type
 ProjectCiCdSetting:
 - group_runners_enabled
+ResourceLabelEvent:
+- id
+- action
+- issue_id
+- merge_request_id
+- label_id
+- user_id
+- created_at
diff --git a/spec/models/label_note_spec.rb b/spec/models/label_note_spec.rb
new file mode 100644
index 00000000000..f69874d94aa
--- /dev/null
+++ b/spec/models/label_note_spec.rb
@@ -0,0 +1,23 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe LabelNote do
+  set(:project)  { create(:project, :repository) }
+  set(:user)   { create(:user) }
+  set(:label) { create(:label, project: project) }
+  set(:label2) { create(:label, project: project) }
+  let(:resource_parent) { project }
+
+  context 'when resource is issue' do
+    set(:resource) { create(:issue, project: project) }
+
+    it_behaves_like 'label note created from events'
+  end
+
+  context 'when resource is merge request' do
+    set(:resource) { create(:merge_request, source_project: project, target_project: project) }
+
+    it_behaves_like 'label note created from events'
+  end
+end
diff --git a/spec/models/resource_label_event_spec.rb b/spec/models/resource_label_event_spec.rb
index 4756caa1b97..da6e1b5610d 100644
--- a/spec/models/resource_label_event_spec.rb
+++ b/spec/models/resource_label_event_spec.rb
@@ -3,7 +3,7 @@
 require 'rails_helper'
 
 RSpec.describe ResourceLabelEvent, type: :model do
-  subject { build(:resource_label_event) }
+  subject { build(:resource_label_event, issue: issue) }
   let(:issue) { create(:issue) }
   let(:merge_request) { create(:merge_request) }
 
@@ -16,8 +16,6 @@ RSpec.describe ResourceLabelEvent, type: :model do
 
   describe 'validations' do
     it { is_expected.to be_valid }
-    it { is_expected.to validate_presence_of(:label) }
-    it { is_expected.to validate_presence_of(:user) }
 
     describe 'Issuable validation' do
       it 'is invalid if issue_id and merge_request_id are missing' do
@@ -45,4 +43,52 @@ RSpec.describe ResourceLabelEvent, type: :model do
       end
     end
   end
+
+  describe '#expire_etag_cache' do
+    def expect_expiration(issue)
+      expect_any_instance_of(Gitlab::EtagCaching::Store)
+        .to receive(:touch)
+        .with("/#{issue.project.namespace.to_param}/#{issue.project.to_param}/noteable/issue/#{issue.id}/notes")
+    end
+
+    it 'expires resource note etag cache on event save' do
+      expect_expiration(subject.issuable)
+
+      subject.save!
+    end
+
+    it 'expires resource note etag cache on event destroy' do
+      subject.save!
+
+      expect_expiration(subject.issuable)
+
+      subject.destroy!
+    end
+  end
+
+  describe '#outdated_markdown?' do
+    it 'returns true if label is missing and reference is not empty' do
+      subject.attributes = { reference: 'ref', label_id: nil }
+
+      expect(subject.outdated_markdown?).to be true
+    end
+
+    it 'returns true if reference is not set yet' do
+      subject.attributes = { reference: nil }
+
+      expect(subject.outdated_markdown?).to be true
+    end
+
+    it 'returns true markdown is outdated' do
+      subject.attributes = { cached_markdown_version: 0 }
+
+      expect(subject.outdated_markdown?).to be true
+    end
+
+    it 'returns false if label and reference are set' do
+      subject.attributes = { reference: 'whatever', cached_markdown_version: CacheMarkdownField::CACHE_COMMONMARK_VERSION  }
+
+      expect(subject.outdated_markdown?).to be false
+    end
+  end
 end
diff --git a/spec/requests/api/resource_label_events_spec.rb b/spec/requests/api/resource_label_events_spec.rb
new file mode 100644
index 00000000000..b7d4a5152cc
--- /dev/null
+++ b/spec/requests/api/resource_label_events_spec.rb
@@ -0,0 +1,75 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe API::ResourceLabelEvents do
+  set(:user) { create(:user) }
+  set(:project) { create(:project, :public, :repository, namespace: user.namespace) }
+  set(:private_user)    { create(:user) }
+
+  before do
+    project.add_developer(user)
+  end
+
+  shared_examples 'resource_label_events API' do |parent_type, eventable_type, id_name|
+    describe "GET /#{parent_type}/:id/#{eventable_type}/:noteable_id/resource_label_events" do
+      it "returns an array of resource label events" do
+        get api("/#{parent_type}/#{parent.id}/#{eventable_type}/#{eventable[id_name]}/resource_label_events", user)
+
+        expect(response).to have_gitlab_http_status(200)
+        expect(response).to include_pagination_headers
+        expect(json_response).to be_an Array
+        expect(json_response.first['id']).to eq(event.id)
+      end
+
+      it "returns a 404 error when eventable id not found" do
+        get api("/#{parent_type}/#{parent.id}/#{eventable_type}/12345/resource_label_events", user)
+
+        expect(response).to have_gitlab_http_status(404)
+      end
+
+      it "returns 404 when not authorized" do
+        parent.update!(visibility_level: Gitlab::VisibilityLevel::PRIVATE)
+
+        get api("/#{parent_type}/#{parent.id}/#{eventable_type}/#{eventable[id_name]}/resource_label_events", private_user)
+
+        expect(response).to have_gitlab_http_status(404)
+      end
+    end
+
+    describe "GET /#{parent_type}/:id/#{eventable_type}/:noteable_id/resource_label_events/:event_id" do
+      it "returns a resource label event by id" do
+        get api("/#{parent_type}/#{parent.id}/#{eventable_type}/#{eventable[id_name]}/resource_label_events/#{event.id}", user)
+
+        expect(response).to have_gitlab_http_status(200)
+        expect(json_response['id']).to eq(event.id)
+      end
+
+      it "returns a 404 error if resource label event not found" do
+        get api("/#{parent_type}/#{parent.id}/#{eventable_type}/#{eventable[id_name]}/resource_label_events/12345", user)
+
+        expect(response).to have_gitlab_http_status(404)
+      end
+    end
+  end
+
+  context 'when eventable is an Issue' do
+    let(:issue) { create(:issue, project: project, author: user) }
+
+    it_behaves_like 'resource_label_events API', 'projects', 'issues', 'iid' do
+      let(:parent) { project }
+      let(:eventable) { issue }
+      let!(:event) { create(:resource_label_event, issue: issue) }
+    end
+  end
+
+  context 'when eventable is a Merge Request' do
+    let(:merge_request) { create(:merge_request, source_project: project, target_project: project, author: user) }
+
+    it_behaves_like 'resource_label_events API', 'projects', 'merge_requests', 'iid' do
+      let(:parent) { project }
+      let(:eventable) { merge_request }
+      let!(:event) { create(:resource_label_event, merge_request: merge_request) }
+    end
+  end
+end
diff --git a/spec/services/issuable/common_system_notes_service_spec.rb b/spec/services/issuable/common_system_notes_service_spec.rb
index dcf4503ef9c..fa1a421d528 100644
--- a/spec/services/issuable/common_system_notes_service_spec.rb
+++ b/spec/services/issuable/common_system_notes_service_spec.rb
@@ -12,12 +12,21 @@ describe Issuable::CommonSystemNotesService do
     it_behaves_like 'system note creation', { time_estimate: 5 }, 'changed time estimate'
 
     context 'when new label is added' do
+      let(:label) { create(:label, project: project) }
+
       before do
-        label = create(:label, project: project)
         issuable.labels << label
+        issuable.save
       end
 
-      it_behaves_like 'system note creation', {}, /added ~\w+ label/
+      it 'creates a resource label event' do
+        described_class.new(project, user).execute(issuable, [])
+        event = issuable.reload.resource_label_events.last
+
+        expect(event).not_to be_nil
+        expect(event.label_id).to eq label.id
+        expect(event.user_id).to eq user.id
+      end
     end
 
     context 'when new milestone is assigned' do
diff --git a/spec/services/issues/move_service_spec.rb b/spec/services/issues/move_service_spec.rb
index 609eef76d2c..b5767583952 100644
--- a/spec/services/issues/move_service_spec.rb
+++ b/spec/services/issues/move_service_spec.rb
@@ -122,6 +122,17 @@ describe Issues::MoveService do
         end
       end
 
+      context 'issue with resource label events' do
+        it 'assigns resource label events to new issue' do
+          old_issue.resource_label_events = create_list(:resource_label_event, 2, issue: old_issue)
+
+          new_issue = move_service.execute(old_issue, new_project)
+
+          expected = old_issue.resource_label_events.map(&:label_id)
+          expect(new_issue.resource_label_events.map(&:label_id)).to match_array(expected)
+        end
+      end
+
       context 'generic issue' do
         include_context 'issue move executed'
 
diff --git a/spec/services/issues/update_service_spec.rb b/spec/services/issues/update_service_spec.rb
index 5bcfef46b75..07aa8449a66 100644
--- a/spec/services/issues/update_service_spec.rb
+++ b/spec/services/issues/update_service_spec.rb
@@ -189,11 +189,12 @@ describe Issues::UpdateService, :mailer do
           expect(note.note).to include "assigned to #{user2.to_reference}"
         end
 
-        it 'creates system note about issue label edit' do
-          note = find_note('added ~')
+        it 'creates a resource label event' do
+          event = issue.resource_label_events.last
 
-          expect(note).not_to be_nil
-          expect(note.note).to include "added #{label.to_reference} label"
+          expect(event).not_to be_nil
+          expect(event.label_id).to eq label.id
+          expect(event.user_id).to eq user.id
         end
 
         it 'creates system note about title change' do
diff --git a/spec/services/merge_requests/update_service_spec.rb b/spec/services/merge_requests/update_service_spec.rb
index f0029af83cc..55dfab81c26 100644
--- a/spec/services/merge_requests/update_service_spec.rb
+++ b/spec/services/merge_requests/update_service_spec.rb
@@ -109,11 +109,12 @@ describe MergeRequests::UpdateService, :mailer do
         expect(note.note).to include "assigned to #{user2.to_reference}"
       end
 
-      it 'creates system note about merge_request label edit' do
-        note = find_note('added ~')
+      it 'creates a resource label event' do
+        event = merge_request.resource_label_events.last
 
-        expect(note).not_to be_nil
-        expect(note.note).to include "added #{label.to_reference} label"
+        expect(event).not_to be_nil
+        expect(event.label_id).to eq label.id
+        expect(event.user_id).to eq user.id
       end
 
       it 'creates system note about title change' do
diff --git a/spec/services/resource_events/change_labels_service_spec.rb b/spec/services/resource_events/change_labels_service_spec.rb
index 41b0fb3eea3..4c9138fb1ef 100644
--- a/spec/services/resource_events/change_labels_service_spec.rb
+++ b/spec/services/resource_events/change_labels_service_spec.rb
@@ -18,6 +18,14 @@ describe ResourceEvents::ChangeLabelsService do
       expect(event.action).to eq(action)
     end
 
+    it 'expires resource note etag cache' do
+      expect_any_instance_of(Gitlab::EtagCaching::Store)
+        .to receive(:touch)
+        .with("/#{resource.project.namespace.to_param}/#{resource.project.to_param}/noteable/issue/#{resource.id}/notes")
+
+      described_class.new(resource, author).execute(added_labels: [labels[0]])
+    end
+
     context 'when adding a label' do
       let(:added)   { [labels[0]] }
       let(:removed) { [] }
diff --git a/spec/services/resource_events/merge_into_notes_service_spec.rb b/spec/services/resource_events/merge_into_notes_service_spec.rb
new file mode 100644
index 00000000000..0d333d541c9
--- /dev/null
+++ b/spec/services/resource_events/merge_into_notes_service_spec.rb
@@ -0,0 +1,70 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe ResourceEvents::MergeIntoNotesService do
+  def create_event(params)
+    event_params = { action: :add, label: label, issue: resource,
+                     user: user }
+
+    create(:resource_label_event, event_params.merge(params))
+  end
+
+  def create_note(params)
+    opts = { noteable: resource, project: project }
+
+    create(:note_on_issue, opts.merge(params))
+  end
+
+  set(:project)  { create(:project) }
+  set(:user)   { create(:user) }
+  set(:resource) { create(:issue, project: project) }
+  set(:label) { create(:label, project: project) }
+  set(:label2) { create(:label, project: project) }
+  let(:time) { Time.now }
+
+  describe '#execute' do
+    it 'merges label events into notes in order of created_at' do
+      note1 = create_note(created_at: 4.days.ago)
+      note2 = create_note(created_at: 2.days.ago)
+      event1 = create_event(created_at: 3.days.ago)
+      event2 = create_event(created_at: 1.day.ago)
+
+      notes = described_class.new(resource, user).execute([note1, note2])
+
+      expected = [note1, event1, note2, event2].map(&:discussion_id)
+      expect(notes.map(&:discussion_id)).to eq expected
+    end
+
+    it 'squashes events with same time and author into single note' do
+      user2 = create(:user)
+
+      create_event(created_at: time)
+      create_event(created_at: time, label: label2, action: :remove)
+      create_event(created_at: time, user: user2)
+      create_event(created_at: 1.day.ago, label: label2)
+
+      notes = described_class.new(resource, user).execute()
+
+      expected = [
+        "added #{label.to_reference} label and removed #{label2.to_reference} label",
+        "added #{label.to_reference} label",
+        "added #{label2.to_reference} label"
+      ]
+
+      expect(notes.count).to eq 3
+      expect(notes.map(&:note)).to match_array expected
+    end
+
+    it 'fetches only notes created after last_fetched_at' do
+      create_event(created_at: 4.days.ago)
+      event = create_event(created_at: 1.day.ago)
+
+      notes = described_class.new(resource, user,
+                                  last_fetched_at: 2.days.ago.to_i).execute()
+
+      expect(notes.count).to eq 1
+      expect(notes.first.discussion_id).to eq event.discussion_id
+    end
+  end
+end
diff --git a/spec/services/system_note_service_spec.rb b/spec/services/system_note_service_spec.rb
index 48aad8ebdbe..d5d750e182b 100644
--- a/spec/services/system_note_service_spec.rb
+++ b/spec/services/system_note_service_spec.rb
@@ -197,45 +197,6 @@ describe SystemNoteService do
     end
   end
 
-  describe '.change_label' do
-    subject { described_class.change_label(noteable, project, author, added, removed) }
-
-    let(:labels)  { create_list(:label, 2, project: project) }
-    let(:added)   { [] }
-    let(:removed) { [] }
-
-    it_behaves_like 'a system note' do
-      let(:action) { 'label' }
-    end
-
-    context 'with added labels' do
-      let(:added)   { labels }
-      let(:removed) { [] }
-
-      it 'sets the note text' do
-        expect(subject.note).to eq "added ~#{labels[0].id} ~#{labels[1].id} labels"
-      end
-    end
-
-    context 'with removed labels' do
-      let(:added)   { [] }
-      let(:removed) { labels }
-
-      it 'sets the note text' do
-        expect(subject.note).to eq "removed ~#{labels[0].id} ~#{labels[1].id} labels"
-      end
-    end
-
-    context 'with added and removed labels' do
-      let(:added)   { [labels[0]] }
-      let(:removed) { [labels[1]] }
-
-      it 'sets the note text' do
-        expect(subject.note).to eq "added ~#{labels[0].id} and removed ~#{labels[1].id} labels"
-      end
-    end
-  end
-
   describe '.change_milestone' do
     context 'for a project milestone' do
       subject { described_class.change_milestone(noteable, project, author, milestone) }
diff --git a/spec/support/shared_examples/models/label_note_shared_examples.rb b/spec/support/shared_examples/models/label_note_shared_examples.rb
new file mode 100644
index 00000000000..5803b3af74b
--- /dev/null
+++ b/spec/support/shared_examples/models/label_note_shared_examples.rb
@@ -0,0 +1,109 @@
+# frozen_string_literal: true
+
+shared_examples 'label note created from events' do
+  def create_event(params = {})
+    event_params = { action: :add, label: label, user: user }
+    resource_key = resource.class.name.underscore.to_s
+    event_params[resource_key] = resource
+
+    build(:resource_label_event, event_params.merge(params))
+  end
+
+  def label_refs(events)
+    sorted_labels = events.map(&:label).compact.sort_by(&:title)
+
+    sorted_labels.map { |l| l.to_reference}.join(' ')
+  end
+
+  let(:time) { Time.now }
+  let(:local_label_ids) { [label.id, label2.id] }
+
+  describe '.from_events' do
+    it 'returns system note with expected attributes' do
+      event = create_event
+
+      note = described_class.from_events([event, create_event])
+
+      expect(note.system).to be true
+      expect(note.author_id).to eq event.user_id
+      expect(note.discussion_id).to eq event.discussion_id
+      expect(note.noteable).to eq event.issuable
+      expect(note.note).to be_present
+      expect(note.note_html).to be_present
+    end
+
+    it 'updates markdown cache if reference is not set yet' do
+      event = create_event(reference: nil)
+
+      described_class.from_events([event])
+
+      expect(event.reference).not_to be_nil
+    end
+
+    it 'updates markdown cache if label was deleted' do
+      event = create_event(reference: 'some_ref', label: nil)
+
+      described_class.from_events([event])
+
+      expect(event.reference).to eq ''
+    end
+
+    it 'returns html note' do
+      events = [create_event(created_at: time)]
+
+      note = described_class.from_events(events)
+
+      expect(note.note_html).to include label.title
+    end
+
+    it 'returns text note for added labels' do
+      events = [create_event(created_at: time),
+                create_event(created_at: time, label: label2),
+                create_event(created_at: time, label: nil)]
+
+      note = described_class.from_events(events)
+
+      expect(note.note).to eq "added #{label_refs(events)} + 1 deleted label"
+    end
+
+    it 'returns text note for removed labels' do
+      events = [create_event(action: :remove, created_at: time),
+                create_event(action: :remove, created_at: time, label: label2),
+                create_event(action: :remove, created_at: time, label: nil)]
+
+      note = described_class.from_events(events)
+
+      expect(note.note).to eq "removed #{label_refs(events)} + 1 deleted label"
+    end
+
+    it 'returns text note for added and removed labels' do
+      add_events = [create_event(created_at: time),
+                    create_event(created_at: time, label: nil)]
+
+      remove_events = [create_event(action: :remove, created_at: time),
+                       create_event(action: :remove, created_at: time, label: nil)]
+
+      note = described_class.from_events(add_events + remove_events)
+
+      expect(note.note).to eq "added #{label_refs(add_events)} + 1 deleted label and removed #{label_refs(remove_events)} + 1 deleted label"
+    end
+
+    it 'returns text note for cross-project label' do
+      other_label = create(:label)
+      event = create_event(label: other_label)
+
+      note = described_class.from_events([event])
+
+      expect(note.note).to eq "added #{other_label.to_reference(resource_parent)} label"
+    end
+
+    it 'returns text note for cross-group label' do
+      other_label = create(:group_label)
+      event = create_event(label: other_label)
+
+      note = described_class.from_events([event])
+
+      expect(note.note).to eq "added #{other_label.to_reference(other_label.group, target_project: project, full: true)} label"
+    end
+  end
+end