Add confidential_only scop to issue model

app/finders/issues_finder.rb

@@ -73,17 +73,11 @@ class IssuesFinder < IssuableFinder
     by_confidential(issues)
   end
 
-  # rubocop: disable CodeReuse/ActiveRecord
   def by_confidential(items)
-    if params[:confidential] == 'yes'
-      items.where('issues.confidential = TRUE')
-    elsif params[:confidential] == 'no'
-      items.where.not('issues.confidential = TRUE')
-    else
-      items
-    end
+    return items unless params[:confidential].present?
+
+    params[:confidential] == 'yes' ? items.confidential_only : items.public_only
   end
-  # rubocop: enable CodeReuse/ActiveRecord
 
   def by_due_date(items)
     if due_date?

app/models/issue.rb

@@ -66,6 +66,7 @@ class Issue < ActiveRecord::Base
   scope :preload_associations, -> { preload(:labels, project: :namespace) }
 
   scope :public_only, -> { where(confidential: false) }
+  scope :confidential_only, -> { where(confidential: true) }
 
   after_save :expire_etag_cache
   after_save :ensure_metrics, unless: :imported?

spec/models/issue_spec.rb

@@ -765,6 +765,15 @@ describe Issue do
     end
   end
 
+  describe '.confidential_only' do
+    it 'only returns confidential_only issues' do
+      create(:issue)
+      confidential_issue = create(:issue, confidential: true)
+
+      expect(described_class.confidential_only).to eq([confidential_issue])
+    end
+  end
+
   it_behaves_like 'throttled touch' do
     subject { create(:issue, updated_at: 1.hour.ago) }
   end