Fix scope chaining + STI

See #9869 and #9929.

The problem arises from the following example:

    class Project < ActiveRecord::Base
      scope :completed, -> { where completed: true }
    end

    class MajorProject < Project
    end

When calling:

    MajorProject.where(tasks_count: 10).completed

This expands to:

    MajorProject.where(tasks_count: 10).scoping {
      MajorProject.completed
    }

However the lambda for the `completed` scope is defined on Project. This
means that when it is called, `self` is Project rather than
MajorProject. So it expands to:

    MajorProject.where(tasks_count: 10).scoping {
      Project.where(completed: true)
    }

Since the scoping was applied on MajorProject, and not Project, this
fails to apply the tasks_count condition.

The solution is to make scoping apply across STI classes. I am slightly
concerned about the possible side-effects of this, but no tests fail and
it seems ok. I guess we'll see.

1 files changed, 1 insertions, 1 deletions

diff --git a/activerecord/test/cases/scoping/named_scoping_test.rb b/activerecord/test/cases/scoping/named_scoping_test.rb
index 1ac68746de..afe32af1d1 100644
--- a/activerecord/test/cases/scoping/named_scoping_test.rb
+++ b/activerecord/test/cases/scoping/named_scoping_test.rb
@@ -461,7 +461,7 @@ class NamedScopingTest < ActiveRecord::TestCase
   end
 
   def test_subclass_merges_scopes_properly
-    assert_equal 1, SpecialComment.crazy_all.count
+    assert_equal 1, SpecialComment.where(body: 'go crazy').created.count
   end
 
 end