keep track of the left and right reflections and expose those

activerecord/lib/active_record/associations.rb

@@ -1591,7 +1591,7 @@ def destroy_associations
 
         hm_options = {}
         hm_options[:through] = middle_reflection.name
-        hm_options[:source] = join_model.right_association_name
+        hm_options[:source] = join_model.right_reflection.name
 
         [:before_add, :after_add, :before_remove, :after_remove].each do |k|
           if options.key? k

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

@@ -46,8 +46,8 @@ class << self;
           attr_accessor :class_resolver
           attr_accessor :name
           attr_accessor :table_name_resolver
-          attr_accessor :left_association_name
-          attr_accessor :right_association_name
+          attr_accessor :left_reflection
+          attr_accessor :right_reflection
         end
 
         def self.table_name
@@ -59,14 +59,14 @@ def self.compute_type(class_name)
         end
 
         def self.add_left_association(name, options)
-          self.left_association_name = name
           belongs_to name, options
+          self.left_reflection = reflect_on_association(name)
         end
 
         def self.add_right_association(name, options)
           rhs_name = name.to_s.singularize.to_sym
-          self.right_association_name = rhs_name
           belongs_to rhs_name, options
+          self.right_reflection = reflect_on_association(rhs_name)
         end
 
       }
@@ -96,7 +96,7 @@ def middle_reflection(join_model)
     def middle_options(join_model)
       middle_options = {}
       middle_options[:class] = join_model
-      middle_options[:source] = join_model.left_association_name
+      middle_options[:source] = join_model.left_reflection.name
       if options.key? :foreign_key
         middle_options[:foreign_key] = options[:foreign_key]
       end