Allow global override of default STI inheritance column

This change fixes a bug by which 3.2-STABLE users can't globally override the default STI inheritance column with `ActiveRecord::Base.inheritance_column = 'some_column'`. 3.2-STABLE users are forced to use a deprecated method or monkey patch it otherwise.

Test case written by tkhr <takehiro0740@gmail.com>.

3 files changed, 29 insertions, 1 deletions

diff --git a/activerecord/CHANGELOG.md b/activerecord/CHANGELOG.md
index c673a278f6..3c38b47d2e 100644
--- a/activerecord/CHANGELOG.md
+++ b/activerecord/CHANGELOG.md
@@ -5,6 +5,11 @@
 
     *Janko Marohnić*
 
+*   Fix a bug that prevented the use of the default STI inheritance column
+    (ActiveRecord::Base.inheritance_column = 'some_column'.)
+
+    *chapmajs + Takehiro Adachi*
+
 *   Fix mysql2 adapter raises the correct exception when executing a query on a
     closed connection.
 
diff --git a/activerecord/lib/active_record/model_schema.rb b/activerecord/lib/active_record/model_schema.rb
index e10e6b4aa8..40cc8dcd69 100644
--- a/activerecord/lib/active_record/model_schema.rb
+++ b/activerecord/lib/active_record/model_schema.rb
@@ -159,7 +159,7 @@ module ActiveRecord
       # The name of the column containing the object's class when Single Table Inheritance is used
       def inheritance_column
         if self == Base
-          'type'
+          (@inheritance_column ||= nil) || 'type'
         else
           (@inheritance_column ||= nil) || superclass.inheritance_column
         end
diff --git a/activerecord/test/cases/inheritance_test.rb b/activerecord/test/cases/inheritance_test.rb
index 54c9152c06..99a252a389 100644
--- a/activerecord/test/cases/inheritance_test.rb
+++ b/activerecord/test/cases/inheritance_test.rb
@@ -290,3 +290,26 @@ class InheritanceComputeTypeTest < ActiveRecord::TestCase
     ActiveRecord::Base.store_full_sti_class = true
   end
 end
+
+
+class GlobalInheritanceColumnTest < ActiveRecord::TestCase
+  fixtures :companies
+
+  setup do
+    @inheritance_column = ActiveRecord::Base.inheritance_column
+  end
+
+  teardown do
+    ActiveRecord::Base.inheritance_column = @inheritance_column
+  end
+
+  def test_changing_global_inheritance_column
+    ActiveRecord::Base.inheritance_column = 'ruby_type'
+
+    firm = Firm.create('name' => 'FirmWithAltInheritanceColumn')
+    assert_equal 'Firm', firm.ruby_type
+
+    assert_equal 'ruby_type', Company.inheritance_column
+    assert_equal 'ruby_type', Firm.inheritance_column
+  end
+end