Support pending user count display

Backend support for showing an instance admin pending
users when they remove or increase a user cap on their
instance

app/helpers/application_settings_helper.rb

@@ -447,6 +447,12 @@ module ApplicationSettingsHelper
   def signup_enabled?
     !!Gitlab::CurrentSettings.signup_enabled
   end
+
+  def pending_user_count
+    return 0 if Gitlab::CurrentSettings.new_user_signups_cap.blank?
+
+    User.blocked_pending_approval.count
+  end
 end
 
 ApplicationSettingsHelper.prepend_mod_with('ApplicationSettingsHelper')

app/views/admin/application_settings/_signup.html.haml

@@ -17,4 +17,5 @@
   email_restrictions_enabled: @application_setting[:email_restrictions_enabled].to_s,
   supported_syntax_link_url: 'https://github.com/google/re2/wiki/Syntax',
   email_restrictions: @application_setting.email_restrictions,
-  after_sign_up_text: @application_setting[:after_sign_up_text] } }
+  after_sign_up_text: @application_setting[:after_sign_up_text],
+  pending_user_count: pending_user_count } }

spec/helpers/application_settings_helper_spec.rb

@@ -254,4 +254,34 @@ RSpec.describe ApplicationSettingsHelper do
                                            ])
     end
   end
+
+  describe '.pending_user_count' do
+    let(:user_cap) { 200 }
+
+    before do
+      stub_application_setting(new_user_signups_cap: user_cap)
+    end
+
+    subject(:pending_user_count) { helper.pending_user_count }
+
+    context 'when new_user_signups_cap is present' do
+      it 'returns the number of blocked pending users' do
+        create(:user, state: :blocked_pending_approval)
+
+        expect(pending_user_count).to eq 1
+      end
+    end
+
+    context 'when the new_user_signups_cap is not present' do
+      let(:user_cap) { nil }
+
+      it { is_expected.to eq 0 }
+
+      it 'does not query users unnecessarily' do
+        expect(User).not_to receive(:blocked_pending_approval)
+
+        pending_user_count
+      end
+    end
+  end
 end