Fix diff comments not showing up in activity feed

CHANGELOG

@@ -41,6 +41,7 @@ v 8.9.5 (unreleased)
   - Downgrade to Redis 3.2.2 due to massive memory leak with Sidekiq
   - Fixes issues importing events in Import/Export. Import/Export version bumped to 0.1.1
   - Fix import button disabled when import process fail due to the namespace already been taken.
+  - Fix diff comments not showing up in activity feed. !5069
   - Security: Update RedCloth to 4.3.2 (Takuya Noguchi)
 
 v 8.9.4

app/models/event.rb

@@ -67,7 +67,7 @@ class Event < ActiveRecord::Base
     elsif issue? || issue_note?
       Ability.abilities.allowed?(user, :read_issue, note? ? note_target : target)
     else
-      ((merge_request? || note?) && target) || milestone?
+      ((merge_request? || note?) && target.present?) || milestone?
     end
   end
 
@@ -136,7 +136,7 @@ class Event < ActiveRecord::Base
   end
 
   def note?
-    target_type == "Note"
+    %w[Note LegacyDiffNote].include?(target_type)
   end
 
   def issue?

spec/models/event_spec.rb

@@ -46,6 +46,22 @@ describe Event, models: true do
     it { expect(@event.author).to eq(@user) }
   end
 
+  describe '#note?' do
+    subject { Event.new(project: target.project, target: target) }
+
+    context 'issue note event' do
+      let(:target) { create(:note_on_issue) }
+
+      it { is_expected.to be_note }
+    end
+
+    context 'merge request note event' do
+      let(:target) { create(:note_on_merge_request) }
+
+      it { is_expected.to be_note }
+    end
+  end
+
   describe '#visible_to_user?' do
     let(:project) { create(:empty_project, :public) }
     let(:non_member) { create(:user) }
@@ -89,7 +105,7 @@ describe Event, models: true do
       end
     end
 
-    context 'note event' do
+    context 'issue note event' do
       context 'on non confidential issues' do
         let(:target) { note_on_issue }
 
@@ -112,6 +128,20 @@ describe Event, models: true do
         it { expect(event.visible_to_user?(admin)).to eq true }
       end
     end
+
+    context 'merge request note event' do
+      let(:project) { create(:project, :public) }
+      let(:merge_request) { create(:merge_request, source_project: project, author: author, assignee: assignee) }
+      let(:note_on_merge_request) { create(:note_on_merge_request, noteable: merge_request, project: project) }
+      let(:target) { note_on_merge_request }
+
+      it { expect(event.visible_to_user?(non_member)).to eq true }
+      it { expect(event.visible_to_user?(author)).to eq true }
+      it { expect(event.visible_to_user?(assignee)).to eq true }
+      it { expect(event.visible_to_user?(member)).to eq true }
+      it { expect(event.visible_to_user?(guest)).to eq true }
+      it { expect(event.visible_to_user?(admin)).to eq true }
+    end
   end
 
   describe '.limit_recent' do