Hide `repository_mirrors` attributes from API

When the feature is not available

lib/api/entities.rb

@@ -745,7 +745,10 @@ module API
 
     class ApplicationSetting < Grape::Entity
       expose :id
-      expose(*::ApplicationSettingsHelper.visible_attributes)
+      expose(*ApplicationSettingsHelper.visible_attributes)
+      expose(*EE::ApplicationSettingsHelper.repository_mirror_attributes, if: lambda do |_instance, _options|
+        ::License.feature_available?(:repository_mirrors)
+      end)
       expose(:restricted_visibility_levels) do |setting, _options|
         setting.restricted_visibility_levels.map { |level| Gitlab::VisibilityLevel.string_level(level) }
       end

lib/api/settings.rb

@@ -137,11 +137,17 @@ module API
       optional :repository_storages, type: Array[String], desc: 'A list of names of enabled storage paths, taken from `gitlab.yml`. New projects will be created in one of these stores, chosen at random.'
       optional :repository_size_limit, type: Integer, desc: 'Size limit per repository (MB)'
 
-      at_least_one_of(*::ApplicationSettingsHelper.visible_attributes)
+      all_attributes = ::EE::ApplicationSettingsHelper.repository_mirror_attributes + ApplicationSettingsHelper.visible_attributes
+      optional(*all_attributes)
+      at_least_one_of(*all_attributes)
     end
     put "application/settings" do
       attrs = declared_params(include_missing: false)
 
+      unless ::License.feature_available?(:repository_mirrors)
+        attrs = attrs.except(*::EE::ApplicationSettingsHelper.repository_mirror_attributes)
+      end
+
       if attrs.has_key?(:signin_enabled)
         attrs[:password_authentication_enabled] = attrs.delete(:signin_enabled)
       end

spec/requests/api/ee/settings_spec.rb

 require 'spec_helper'
 
 describe API::Settings, 'EE Settings' do # rubocop:disable RSpec/FilePath
+  include StubENV
+
   let(:user) { create(:user) }
   let(:admin) { create(:admin) }
 
+  before do
+    stub_env('IN_MEMORY_APPLICATION_SETTINGS', 'false')
+  end
+
   describe "PUT /application/settings" do
     it 'sets EE specific settings' do
       put api("/application/settings", admin), help_text: 'Help text'
@@ -12,4 +18,42 @@ describe API::Settings, 'EE Settings' do # rubocop:disable RSpec/FilePath
       expect(json_response['help_text']).to eq('Help text')
     end
   end
+
+  context 'when the repository mirrors feature is not available' do
+    before do
+      stub_licensed_features(repository_mirrors: false)
+      get api("/application/settings", admin)
+    end
+
+    it 'hides repository mirror attributes when the feature is available' do
+      get api("/application/settings", admin)
+
+      expect(response).to have_http_status(200)
+      expect(json_response.keys).not_to include('mirror_max_capacity')
+    end
+
+    it 'does not update repository mirror attributes' do
+      expect { put api("/application/settings", admin), mirror_max_capacity: 15 }
+        .not_to change(ApplicationSetting.current.reload, :mirror_max_capacity)
+    end
+  end
+
+  context 'when the repository mirrors feature is available' do
+    before do
+      stub_licensed_features(repository_mirrors: true)
+    end
+
+    it 'has repository mirror attributes when the feature is available' do
+      get api("/application/settings", admin)
+
+      expect(response).to have_http_status(200)
+      expect(json_response.keys).to include('mirror_max_capacity')
+    end
+
+    it 'updates repository mirror attributes' do
+      put api("/application/settings", admin), mirror_max_capacity: 15
+
+      expect(ApplicationSetting.current.reload.mirror_max_capacity).to eq(15)
+    end
+  end
 end