Create system note on epic date change

ee/app/helpers/ee/system_note_helper.rb

@@ -8,7 +8,8 @@ module EE
       'epic_issue_moved' => 'issues',
       'issue_added_to_epic' => 'epic',
       'issue_removed_from_epic' => 'epic',
-      'issue_changed_epic' => 'epic'
+      'issue_changed_epic' => 'epic',
+      'epic_date_changed' => 'calendar'
     }.freeze
 
     override :system_note_icon_name

ee/app/models/ee/system_note_metadata.rb

@@ -5,7 +5,7 @@ module EE
     EE_ICON_TYPES = %w[
       weight approved unapproved relate unrelate
       epic_issue_added issue_added_to_epic epic_issue_removed issue_removed_from_epic
-      epic_issue_moved issue_changed_epic
+      epic_issue_moved issue_changed_epic epic_date_changed
     ].freeze
 
     override :icon_types

ee/app/services/ee/issuable/common_system_notes_service.rb

@@ -8,10 +8,21 @@ module EE
       def execute(_issuable, _old_labels)
         super
         handle_weight_change_note
+        handle_date_change_note
       end
 
       private
 
+      def handle_date_change_note
+        if issuable.previous_changes.include?('start_date')
+          ::SystemNoteService.change_epic_date_note(issuable, current_user, 'start date', issuable['start_date'])
+        end
+
+        if issuable.previous_changes.include?('end_date')
+          ::SystemNoteService.change_epic_date_note(issuable, current_user, 'finish date', issuable['end_date'])
+        end
+      end
+
       def handle_weight_change_note
         if issuable.previous_changes.include?('weight')
           create_weight_change_note

ee/app/services/ee/system_note_service.rb

@@ -24,5 +24,27 @@ module EE
       body = noteable.weight ? "changed weight to **#{noteable.weight}**," : 'removed the weight'
       create_note(NoteSummary.new(noteable, project, author, body, action: 'weight'))
     end
+
+    # Called when the start or end date of an Issuable is changed
+    #
+    # noteable   - Noteable object
+    # author     - User performing the change
+    # date_type  - 'start date' or 'finish date'
+    # date       - New date
+    #
+    # Example Note text:
+    #
+    #   "changed start date to FIXME"
+    #
+    # Returns the created Note object
+    def change_epic_date_note(noteable, author, date_type, date)
+      body = if date
+               "changed #{date_type} to #{date.strftime('%b %-d, %Y')}"
+             else
+               "removed the #{date_type}"
+             end
+
+      create_note(NoteSummary.new(noteable, nil, author, body, action: 'epic_date_changed'))
+    end
   end
 end

ee/changelogs/unreleased/ee-epic-date-note.yml

+---
+title: Create system note on epic date change.
+merge_request:
+author:
+type: added

ee/spec/services/ee/issuable/common_system_notes_service_spec.rb

@@ -7,5 +7,24 @@ describe Issuable::CommonSystemNotesService do
 
   describe '#execute' do
     it_behaves_like 'system note creation', { weight: 5 }, 'changed weight to **5**,'
+
+    context 'when issuable is an epic' do
+      let(:timestamp) { Time.now }
+      let(:issuable) { create(:epic, end_date: timestamp) }
+
+      subject { described_class.new(nil, user).execute(issuable, [])}
+
+      before do
+        issuable.assign_attributes(start_date: timestamp, end_date: nil)
+        issuable.save
+      end
+
+      it 'creates 2 system notes with the correct content' do
+        expect { subject }.to change { Note.count }.from(0).to(2)
+
+        expect(Note.first.note).to match("changed start date to #{timestamp.strftime('%b %-d, %Y')}")
+        expect(Note.second.note).to match('removed the finish date')
+      end
+    end
   end
 end

ee/spec/services/system_note_service_spec.rb

@@ -21,20 +21,28 @@ describe SystemNoteService do
       expect(subject).to be_system
 
       expect(subject.noteable).to eq expected_noteable
-      expect(subject.project).to eq project
       expect(subject.author).to eq author
 
       expect(subject.system_note_metadata.action).to eq(action)
       expect(subject.system_note_metadata.commit_count).to eq(commit_count)
     end
   end
+
+  shared_examples_for 'a project system note' do
+    it 'has the project attribute set' do
+      expect(subject.project).to eq project
+    end
+
+    it_behaves_like 'a system note'
+  end
+
   describe '.change_weight_note' do
     context 'when weight changed' do
       let(:noteable) { create(:issue, project: project, title: 'Lorem ipsum', weight: 4) }
 
       subject { described_class.change_weight_note(noteable, project, author) }
 
-      it_behaves_like 'a system note' do
+      it_behaves_like 'a project system note' do
         let(:action) { 'weight' }
       end
 
@@ -48,7 +56,7 @@ describe SystemNoteService do
 
       subject { described_class.change_weight_note(noteable, project, author) }
 
-      it_behaves_like 'a system note' do
+      it_behaves_like 'a project system note' do
         let(:action) { 'weight' }
       end
 
@@ -57,4 +65,36 @@ describe SystemNoteService do
       end
     end
   end
+
+  describe '.change_epic_date_note' do
+    let(:timestamp) { Time.now }
+
+    context 'when start date was changed' do
+      let(:noteable) { create(:epic) }
+
+      subject { described_class.change_epic_date_note(noteable, author, 'start date', timestamp) }
+
+      it_behaves_like 'a system note' do
+        let(:action) { 'epic_date_changed' }
+      end
+
+      it 'sets the note text' do
+        expect(subject.note).to eq "changed start date to #{timestamp.strftime('%b %-d, %Y')}"
+      end
+    end
+
+    context 'when start date was removed' do
+      let(:noteable) { create(:epic, start_date: timestamp) }
+
+      subject { described_class.change_epic_date_note(noteable, author, 'start date', nil) }
+
+      it_behaves_like 'a system note' do
+        let(:action) { 'epic_date_changed' }
+      end
+
+      it 'sets the note text' do
+        expect(subject.note).to eq 'removed the start date'
+      end
+    end
+  end
 end