Fix DeviseCreateDefaultAdminUser migration for Rails 3.0

lib/generators/active_admin/devise/devise_generator.rb

@@ -35,14 +35,24 @@ def set_namespace_for_path
 
       def add_default_user_to_migration
         # Don't assume that we have a migration!
-        devise_migrations = Dir["db/migrate/*_devise_create_#{table_name}.rb"]
-        if devise_migrations.size > 0
-          inject_into_file  Dir["db/migrate/*_devise_create_#{table_name}.rb"].first, 
+        devise_migration_file = Dir["db/migrate/*_devise_create_#{table_name}.rb"].first
+        return if devise_migration_file.nil?
+
+        devise_migration_content = File.read(devise_migration_file)
+
+        if devise_migration_content["def change"]
+          inject_into_file  devise_migration_file,
                             "def migrate(direction)\n    super\n    # Create a default user\n    AdminUser.create!(:email => 'admin@example.com', :password => 'password', :password_confirmation => 'password') if direction == :up\n  end\n\n  ", 
                             :before => "def change"
+        elsif devise_migration_content[/def (self.)?up/]
+          inject_into_file  devise_migration_file,
+                            "# Create a default user\n    #{class_name}.create!(:email => 'admin@example.com', :password => 'password', :password_confirmation => 'password')\n\n    ",
+                            :before => "add_index :#{table_name}, :email"
+        else
+          puts devise_migration_content
+          raise "Failed to add default admin user to migration."
         end
       end
-
     end
   end
 end