If i use a ldap configuration with

# config/ldap.yml
development:
  base: ou=people,dc=test,dc=com 
  attribute: uid
  group_base: ou=groups,dc=test,dc=com
  required_groups:    
    - ["moreMembers", "cn=users,ou=groups,dc=test,dc=com"]

and I have my dn like

 uid=gmgp,ou=developpers,ou=people,dc=test,dc=com 

in the log the LDAPLogger write

  LDAP: LDAP search: uid=gmgp
  LDAP: Authorizing user uid=gmgp,ou=developpers,ou=people,dc=test,dc=com
  LDAP: LDAP search: uid=gmgp
  LDAP: LDAP search: uid=gmgp
  LDAP: LDAP search: uid=gmgp
  LDAP: User uid=gmgp,ou=people,dc=test,dc=com is not in group: cn=users,ou=groups,dc=test,dc=com

my simple workaround is to create a local attribute

#devise_ldap_authenticatable-0.4.6/lib/devise_ldap_authenticatable/ldap_adapter.rb

27  class LdapConnect
28  
29        attr_reader :ldap, :login, :login_dn

54      def dn
55        DeviseLdapAuthenticatable::Logger.send("LDAP search: #{@attribute}=#{@login}")
56        filter = Net::LDAP::Filter.eq(@attribute.to_s, @login.to_s)
57        ldap_entry = nil
58        @ldap.search(:filter => filter) {|entry| ldap_entry = entry}
59        if ldap_entry.nil?
60          @ldap_auth_username_builder.call(@attribute,@login,@ldap)
61        else       
62          @login_dn = ldap_entry.dn
63        end
64      end

84      def in_required_groups?     
85        return true unless ::Devise.ldap_check_group_membership
86        
      ... 
 99         admin_ldap.search(:base => group_name, :scope => Net::LDAP::SearchScope_BaseObject) do |entry|
100            unless entry[group_attribute].include? @login_dn
101              DeviseLdapAuthenticatable::Logger.send("User #{@login_dn} is not in group: #{group_name }")
102              return false
103            end
104          end
105        end

This workaround works even if it does not solve the underlying problem
I prepare a commit as it should if I find a moment of time