Pass a base relation to build_default_scope when joining

This allows the default scope to be built using the current table alias.
Resolves #12770

2 files changed, 10 insertions, 0 deletions

diff --git a/activerecord/test/cases/associations/inner_join_association_test.rb b/activerecord/test/cases/associations/inner_join_association_test.rb
index a9efa6d86a..b23517b2f9 100644
--- a/activerecord/test/cases/associations/inner_join_association_test.rb
+++ b/activerecord/test/cases/associations/inner_join_association_test.rb
@@ -117,4 +117,13 @@ class InnerJoinAssociationTest < ActiveRecord::TestCase
 
     assert_equal [author], Author.where(id: author).joins(:special_categorizations)
   end
+
+  test "the default scope of the target is correctly aliased when joining associations" do
+    author = Author.create! name: "Jon"
+    author.categories.create! name: 'Not Special'
+    author.special_categories.create! name: 'Special'
+
+    categories = author.categories.includes(:special_categorizations).references(:special_categorizations).to_a
+    assert_equal 2, categories.size
+  end
 end
diff --git a/activerecord/test/models/category.rb b/activerecord/test/models/category.rb
index 7da39a8e33..272223e1d8 100644
--- a/activerecord/test/models/category.rb
+++ b/activerecord/test/models/category.rb
@@ -22,6 +22,7 @@ class Category < ActiveRecord::Base
   end
 
   has_many :categorizations
+  has_many :special_categorizations
   has_many :post_comments, :through => :posts, :source => :comments
 
   has_many :authors, :through => :categorizations