allow has_many :through to work with custom :foreign key (closes #3422) [Rick Olson]

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@3456 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

activerecord/lib/active_record/associations/has_many_through_association.rb

@@ -62,7 +62,6 @@ module ActiveRecord
 
         def construct_conditions
           through_reflection = @owner.class.reflections[@reflection.options[:through]]
-          through_foreign_classname = ActiveRecord::Base.send(:class_name_of_active_record_descendant, @owner.class).to_s
           
           if through_reflection.options[:as]
             conditions = 
@@ -72,7 +71,7 @@ module ActiveRecord
           else
             conditions = 
               "#{@reflection.klass.table_name}.#{@reflection.klass.primary_key} = #{through_reflection.table_name}.#{@reflection.klass.to_s.foreign_key} " +
-              "AND #{through_reflection.table_name}.#{through_foreign_classname.foreign_key} = #{@owner.quoted_id}"
+              "AND #{through_reflection.table_name}.#{through_reflection.primary_key_name} = #{@owner.quoted_id}"
           end
           
           conditions << " AND (#{interpolate_sql(sanitize_sql(@reflection.options[:conditions]))})" if @reflection.options[:conditions]

activerecord/test/associations_join_model_test.rb

@@ -68,5 +68,9 @@ class AssociationsJoinModelTest < Test::Unit::TestCase
     assert_equal categories(:general), authors(:david).categories.find_by_name('General')
 #    assert_equal nil, authors(:david).categories.find_by_name('Technology')
   end
-    
+
+  def test_has_many_going_through_join_model_with_custom_foreign_key
+    assert_equal [], posts(:thinking).authors
+    assert_equal [authors(:mary)], posts(:authorless).authors
+  end
 end

activerecord/test/fixtures/post.rb

@@ -23,6 +23,9 @@ class Post < ActiveRecord::Base
   has_many :taggings, :as => :taggable
   has_many :tags, :through => :taggings
 
+  has_many :categorizations, :foreign_key => :category_id
+  has_many :authors, :through => :categorizations
+
   def self.what_are_you
     'a post...'
   end