repurpose the HABTM builder class

activerecord/lib/active_record/associations.rb

@@ -130,7 +130,6 @@ module Builder #:nodoc:
       autoload :HasOne,              'active_record/associations/builder/has_one'
       autoload :HasMany,             'active_record/associations/builder/has_many'
       autoload :HasAndBelongsToMany, 'active_record/associations/builder/has_and_belongs_to_many'
-      autoload :HABTM, 'active_record/associations/builder/has_and_belongs_to_many'
     end
 
     eager_autoload do
@@ -1566,7 +1565,7 @@ def has_and_belongs_to_many(name, scope = nil, options = {}, &extension)
           scope   = nil
         end
 
-        builder = Builder::HABTM.new name, self, options
+        builder = Builder::HasAndBelongsToMany.new name, self, options
 
         join_model = builder.through_model
 
@@ -1590,9 +1589,7 @@ def destroy_associations
         hm_options[:source] = join_model.right_reflection.name
 
         [:before_add, :after_add, :before_remove, :after_remove].each do |k|
-          if options.key? k
-            hm_options[k] = options[k]
-          end
+          hm_options[k] = options[k] if options.key? k
         end
 
         has_many name, scope, hm_options, &extension

activerecord/lib/active_record/associations/builder/has_and_belongs_to_many.rb

 module ActiveRecord::Associations::Builder
-  class HABTM
+  class HasAndBelongsToMany # :nodoc:
     class JoinTableResolver
       KnownTable = Struct.new :join_table
 
@@ -118,27 +118,4 @@ def belongs_to_options(options)
       rhs_options
     end
   end
-
-  class HasAndBelongsToMany < CollectionAssociation #:nodoc:
-    def macro
-      :has_and_belongs_to_many
-    end
-
-    def valid_options
-      super + [:join_table, :association_foreign_key]
-    end
-
-    def self.define_callbacks(model, reflection)
-      super
-      name = reflection.name
-      model.send(:include, Module.new {
-        class_eval <<-RUBY, __FILE__, __LINE__ + 1
-          def destroy_associations
-            association(:#{name}).delete_all
-            super
-          end
-        RUBY
-      })
-    end
-  end
 end