Added test_has_many_through_has_many_with_has_many_through_habtm_source_reflection and make it pass

activerecord/lib/active_record/associations/through_association_scope.rb

@@ -92,7 +92,11 @@ module ActiveRecord
                   polymorphic_conditions(left, left)
                 )
               when :has_and_belongs_to_many
-                raise NotImplementedError
+                joins << inner_join_sql(
+                  right_table_and_alias,
+                  table_aliases[left].first, left.primary_key_name,
+                  table_aliases[right],      right.klass.primary_key
+                )
             end
           else
             case left.source_reflection.macro
@@ -106,7 +110,7 @@ module ActiveRecord
               when :has_many, :has_one
                 if right.macro == :has_and_belongs_to_many
                   join_table, right_table = table_aliases[right]
-                  right_table_and_alias = table_name_and_alias(right.quoted_table_name, right_table)
+                  right_table_and_alias   = table_name_and_alias(right.quoted_table_name, right_table)
                 else
                   right_table = table_aliases[right]
                 end

activerecord/test/cases/associations/join_model_test.rb

@@ -304,7 +304,7 @@ class AssociationsJoinModelTest < ActiveRecord::TestCase
   end
 
   def test_has_many_going_through_join_model_with_custom_foreign_key
-    assert_equal [], posts(:thinking).authors
+    assert_equal [authors(:bob)], posts(:thinking).authors
     assert_equal [authors(:mary)], posts(:authorless).authors
   end
 

activerecord/test/cases/associations/nested_has_many_through_associations_test.rb

@@ -25,6 +25,7 @@ require 'models/sponsor'
 require 'models/club'
 require 'models/organization'
 require 'models/category'
+require 'models/categorization'
 
 # NOTE: Some of these tests might not really test "nested" HMT associations, as opposed to ones which
 # are just one level deep. But it's all the same thing really, as the "nested" code is being 
@@ -34,7 +35,8 @@ require 'models/category'
 class NestedHasManyThroughAssociationsTest < ActiveRecord::TestCase
   fixtures :authors, :books, :posts, :subscriptions, :subscribers, :tags, :taggings,
            :people, :readers, :references, :jobs, :ratings, :comments, :members, :member_details,
-           :member_types, :sponsors, :clubs, :organizations, :categories, :categories_posts
+           :member_types, :sponsors, :clubs, :organizations, :categories, :categories_posts,
+           :categorizations
 
   # Through associations can either use the has_many or has_one macros.
   # 
@@ -183,6 +185,19 @@ class NestedHasManyThroughAssociationsTest < ActiveRecord::TestCase
     # assert_equal [comments(:greetings), comments(:more_greetings)], categories[1].post_comments
   end
   
+  # has_many through
+  # Source: has_many through a habtm
+  # Through: has_many through
+  def test_has_many_through_has_many_with_has_many_through_habtm_source_reflection
+    assert_equal [comments(:greetings), comments(:more_greetings)], authors(:bob).category_post_comments
+    
+    authors = Author.joins(:category_post_comments).where('comments.id' => comments(:does_it_hurt).id)
+    assert_equal [authors(:david), authors(:mary)], authors
+    
+    comments = Author.joins(:category_post_comments)
+    assert_equal [comments(:greetings), comments(:more_greetings)], comments[2].category_post_comments
+  end
+  
   # TODO: has_many through
   # Source: belongs_to
   # Through: has_many through

activerecord/test/fixtures/categorizations.yml

@@ -15,3 +15,9 @@ mary_thinking_general:
   author_id: 2
   post_id: 2
   category_id: 1
+
+bob_misc_by_bob_technology:
+  id: 4
+  author_id: 3
+  post_id: 8
+  category_id: 2

activerecord/test/models/author.rb

@@ -101,6 +101,7 @@ class Author < ActiveRecord::Base
   belongs_to :author_address_extra, :dependent => :delete, :class_name => "AuthorAddress"
 
   has_many :post_categories, :through => :posts, :source => :categories
+  has_many :category_post_comments, :through => :categories, :source => :post_comments
 
   scope :relation_include_posts, includes(:posts)
   scope :relation_include_tags, includes(:tags)