Backport some recent changes related to LDAP from EE

app/controllers/sessions_controller.rb

@@ -23,12 +23,7 @@ class SessionsController < Devise::SessionsController
   def new
     set_minimum_password_length
-    @ldap_servers =
-      if Gitlab.config.ldap.enabled
-        Gitlab::LDAP::Config.servers
-      else
-        []
-      end
+    @ldap_servers = Gitlab::LDAP::Config.available_servers
     super
   end

config/initializers/omniauth.rb

 if Gitlab::LDAP::Config.enabled?
   module OmniAuth::Strategies
-    server = Gitlab.config.ldap.servers.values.first
-    klass = server['provider_class']
-    const_set(klass, Class.new(LDAP)) unless klass == 'LDAP'
+    Gitlab::LDAP::Config.available_servers.each do |server|
+      # do not redeclare LDAP
+      next if server['provider_name'] == 'ldap'
+      const_set(server['provider_class'], Class.new(LDAP))
+    end
   end
   OmniauthCallbacksController.class_eval do
-    server = Gitlab.config.ldap.servers.values.first
-    alias_method server['provider_name'], :ldap
+    Gitlab::LDAP::Config.available_servers.each do |server|
+      alias_method server['provider_name'], :ldap
+    end
   end
 end

lib/gitlab/ldap/config.rb

@@ -18,6 +18,12 @@ module Gitlab
         Gitlab.config.ldap.servers.values
       end
+      def self.available_servers
+        return [] unless enabled?
+
+        Array.wrap(servers.first)
+      end
+
       def self.providers
         servers.map { |server| server['provider_name'] }
       end