Split batch counting from relation builder

This separates the "relation builder" from the "batch counting" concern.

lib/api/entities.rb

@@ -177,6 +177,7 @@ module API
 
     class BasicProjectDetails < ProjectIdentity
       include ::API::ProjectsRelationBuilder
+      include ::API::ProjectsBatchCounting
 
       expose :default_branch, if: -> (project, options) { Ability.allowed?(options[:current_user], :download_code, project) }
       # Avoids an N+1 query: https://github.com/mbleigh/acts-as-taggable-on/issues/91#issuecomment-168273770

lib/api/projects_batch_counting.rb

+# frozen_string_literal: true
+
+module API
+  module ProjectsBatchCounting
+    extend ActiveSupport::Concern
+
+    class_methods do
+      def forks_counting_projects(projects)
+        projects
+      end
+
+      def execute_batch_counting(projects)
+        ::Projects::BatchForksCountService.new(forks_counting_projects(projects)).refresh_cache
+
+        ::Projects::BatchOpenIssuesCountService.new(projects).refresh_cache
+      end
+    end
+  end
+end

lib/api/projects_relation_builder.rb

@@ -13,23 +13,6 @@ module API
       def preload_relation(projects_relation, options = {})
         projects_relation
       end
-
-      def forks_counting_projects(projects_relation)
-        projects_relation
-      end
-
-      def batch_forks_counting(projects_relation)
-        ::Projects::BatchForksCountService.new(forks_counting_projects(projects_relation)).refresh_cache
-      end
-
-      def batch_open_issues_counting(projects_relation)
-        ::Projects::BatchOpenIssuesCountService.new(projects_relation).refresh_cache
-      end
-
-      def execute_batch_counting(projects_relation)
-        batch_forks_counting(projects_relation)
-        batch_open_issues_counting(projects_relation)
-      end
     end
   end
 end

spec/lib/api/projects_batch_counting_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe API::ProjectsBatchCounting do
+  describe '.execute_batch_counting' do
+    subject do
+      Class.new do
+        include ::API::ProjectsBatchCounting
+      end
+    end
+
+    let(:projects) { create_list(:project, 2) }
+    let(:count_service) { double }
+
+    it 'counts forks' do
+      allow(::Projects::BatchForksCountService).to receive(:new).with(projects).and_return(count_service)
+
+      expect(count_service).to receive(:refresh_cache)
+
+      subject.execute_batch_counting(projects)
+    end
+
+    it 'counts open issues' do
+      allow(::Projects::BatchOpenIssuesCountService).to receive(:new).with(projects).and_return(count_service)
+
+      expect(count_service).to receive(:refresh_cache)
+
+      subject.execute_batch_counting(projects)
+    end
+
+    context 'custom fork counting' do
+      subject do
+        Class.new do
+          include ::API::ProjectsBatchCounting
+          def self.forks_counting_projects(projects)
+            [projects.first]
+          end
+        end
+      end
+
+      it 'counts forks for other projects' do
+        allow(::Projects::BatchForksCountService).to receive(:new).with([projects.first]).and_return(count_service)
+
+        expect(count_service).to receive(:refresh_cache)
+
+        subject.execute_batch_counting(projects)
+      end
+    end
+  end
+end