Merge branch 'winh-eager-issue-epic-ee' into 'master'

Eagerly load Issue-Epic-association

Closes #14738

See merge request gitlab-org/gitlab-ee!15886

ee/app/models/ee/issue.rb

@@ -28,6 +28,12 @@ module EE
       validates :weight, allow_nil: true, numericality: { greater_than_or_equal_to: 0 }
     end
 
+    class_methods do
+      def with_api_entity_associations
+        super.preload(:epic)
+      end
+    end
+
     # override
     def check_for_spam?
       author.bot? || super

ee/spec/lib/ee/api/helpers/issues_helpers_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe API::Helpers::IssuesHelpers do
+  set(:group) { create(:group) }
+  set(:project) { create(:project, group: group) }
+  set(:user) { create(:user) }
+  set(:epic) { create(:epic, group: group) }
+
+  subject(:issues_helpers) { Class.new.include(described_class).new }
+
+  before do
+    allow(issues_helpers).to receive(:current_user).and_return(user)
+
+    group.add_owner(user)
+  end
+
+  describe 'find_issues' do
+    context 'with epics' do
+      before do
+        allow(issues_helpers).to receive(:declared_params).and_return(project_id: project.id)
+      end
+
+      it 'returns results' do
+        issues = create_issues(2, project: project, epic: epic)
+
+        expect(issues_helpers.find_issues.count).to be(issues.count)
+      end
+
+      it 'avoids N+1 queries' do
+        create_issues(2, project: project, epic: epic)
+
+        recorder = ActiveRecord::QueryRecorder.new { issues_helpers.find_issues.map(&:epic) }
+
+        create_issues(4, project: project, epic: epic)
+
+        expect { issues_helpers.find_issues.map(&:epic) }.not_to exceed_query_limit(recorder)
+      end
+    end
+  end
+
+  private
+
+  def create_issues(count, params)
+    (1..count).step do
+      create(:issue, params)
+    end
+  end
+end