Refactor ActiveRecord::Inheritance.base_class logic

Moved logic from class_of_active_record_descendant(class) to the
base_class method. This method was confusing because it required
an argument, but that argument was 'self'.

Moved base_class tests to inheritance_test.rb and added some test
coverage for some untested cases.

activerecord/lib/active_record/inheritance.rb

@@ -41,14 +41,26 @@ def symbolized_sti_name
         @symbolized_sti_name ||= sti_name.present? ? sti_name.to_sym : symbolized_base_class
       end
 
-      # Returns the base AR subclass that this class descends from. If A
-      # extends AR::Base, A.base_class will return A. If B descends from A
+      # Returns the class descending directly from ActiveRecord::Base (or
+      # that includes ActiveRecord::Model), or an  abstract class, if any, in
+      # the inheritance hierarchy.
+      #
+      # If A extends AR::Base, A.base_class will return A. If B descends from A
       # through some arbitrarily deep hierarchy, B.base_class will return A.
       #
       # If B < A and C < B and if A is an abstract_class then both B.base_class
       # and C.base_class would return B as the answer since A is an abstract_class.
       def base_class
-        class_of_active_record_descendant(self)
+        unless self < Model::Tag
+          raise ActiveRecordError, "#{name} doesn't belong in a hierarchy descending from ActiveRecord"
+        end
+
+        sup = active_record_super
+        if sup.in?([Base, Model]) || sup.abstract_class?
+          self
+        else
+          sup.base_class
+        end
       end
 
       # Set this to true if this is an abstract class (see <tt>abstract_class?</tt>).
@@ -96,21 +108,6 @@ def active_record_super #:nodoc:
 
       protected
 
-      # Returns the class descending directly from ActiveRecord::Base or an
-      # abstract class, if any, in the inheritance hierarchy.
-      def class_of_active_record_descendant(klass)
-        unless klass < Model::Tag
-          raise ActiveRecordError, "#{name} doesn't belong in a hierarchy descending from ActiveRecord"
-        end
-
-        sup = klass.active_record_super
-        if [Base, Model].include?(klass) || [Base, Model].include?(sup) || sup.abstract_class?
-          klass
-        else
-          class_of_active_record_descendant(sup)
-        end
-      end
-
       # Returns the class type of the record using the current module as a prefix. So descendants of
       # MyApp::Business::Account would appear as MyApp::Business::AccountSubclass.
       def compute_type(type_name)

activerecord/test/cases/base_test.rb

@@ -1619,18 +1619,6 @@ def test_abstract_class_table_name
     assert_nil AbstractCompany.table_name
   end
 
-  def test_base_class
-    assert_equal LoosePerson,     LoosePerson.base_class
-    assert_equal LooseDescendant, LooseDescendant.base_class
-    assert_equal TightPerson,     TightPerson.base_class
-    assert_equal TightPerson,     TightDescendant.base_class
-
-    assert_equal Post, Post.base_class
-    assert_equal Post, SpecialPost.base_class
-    assert_equal Post, StiPost.base_class
-    assert_equal SubStiPost, SubStiPost.base_class
-  end
-
   def test_descends_from_active_record
     assert !ActiveRecord::Base.descends_from_active_record?
 

activerecord/test/cases/inheritance_test.rb

@@ -1,7 +1,10 @@
 require "cases/helper"
 require 'models/company'
+require 'models/person'
+require 'models/post'
 require 'models/project'
 require 'models/subscriber'
+require 'models/teapot'
 
 class InheritanceTest < ActiveRecord::TestCase
   fixtures :companies, :projects, :subscribers, :accounts
@@ -70,6 +73,33 @@ def test_company_descends_from_active_record
     assert !Class.new(Company).descends_from_active_record?, 'Company subclass should not descend from ActiveRecord::Base'
   end
 
+  def test_inheritance_base_class
+    assert_equal Post, Post.base_class
+    assert_equal Post, SpecialPost.base_class
+    assert_equal Post, StiPost.base_class
+    assert_equal SubStiPost, SubStiPost.base_class
+  end
+
+  def test_active_record_model_included_base_class
+    assert_equal Teapot, Teapot.base_class
+  end
+
+  def test_abstract_inheritance_base_class
+    assert_equal LoosePerson, LoosePerson.base_class
+    assert_equal LooseDescendant, LooseDescendant.base_class
+    assert_equal TightPerson, TightPerson.base_class
+    assert_equal TightPerson, TightDescendant.base_class
+  end
+
+  def test_base_class_activerecord_error
+    klass = Class.new {
+      extend ActiveRecord::Configuration
+      include ActiveRecord::Inheritance
+    }
+
+    assert_raise(ActiveRecord::ActiveRecordError) { klass.base_class }
+  end
+
   def test_a_bad_type_column
     #SQLServer need to turn Identity Insert On before manually inserting into the Identity column
     if current_adapter?(:SybaseAdapter)