Extract common logic into a method

activerecord/lib/active_record/attribute_methods.rb

@@ -61,7 +61,7 @@ module ActiveRecord
           raise DangerousAttributeError, "#{method_name} is defined by ActiveRecord"
         end
 
-        if superclass == Base
+        if active_record_super == Base
           super
         else
           # If B < A and A defines its own attribute method, then we don't want to overwrite that.

activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb

@@ -371,12 +371,7 @@ connection.  For example: ActiveRecord::Base.connection.close
         pool = @class_to_pool[klass.name]
         return pool if pool
         return nil if ActiveRecord::Base == klass
-
-        if klass.superclass && klass.superclass < Model
-          retrieve_connection_pool klass.superclass
-        else
-          retrieve_connection_pool ActiveRecord::Base
-        end
+        retrieve_connection_pool klass.active_record_super
       end
     end
 

activerecord/lib/active_record/core.rb

@@ -116,13 +116,7 @@ module ActiveRecord
           if self == ActiveRecord::Base
             ActiveRecord::Base
           else
-            if connection_handler.connection_pools[name]
-              self
-            elsif superclass < ActiveRecord::Model
-              superclass.arel_engine
-            else
-              ActiveRecord::Base
-            end
+            connection_handler.connection_pools[name] ? self : active_record_super.arel_engine
           end
         end
       end

activerecord/lib/active_record/inheritance.rb

@@ -13,12 +13,12 @@ module ActiveRecord
     module ClassMethods
       # True if this isn't a concrete subclass needing a STI type condition.
       def descends_from_active_record?
-        if !(superclass < Model)
-          true
-        elsif superclass.abstract_class?
-          superclass.descends_from_active_record?
+        sup = active_record_super
+
+        if sup.abstract_class?
+          sup.descends_from_active_record?
         else
-          superclass == Base || !columns_hash.include?(inheritance_column)
+          sup == Base || !columns_hash.include?(inheritance_column)
         end
       end
 
@@ -81,6 +81,20 @@ module ActiveRecord
         instance
       end
 
+      # If this class includes ActiveRecord::Model then it won't have a
+      # superclass. So this provides a way to get to the 'root' (ActiveRecord::Base),
+      # through inheritance hierarchy, ending in Base, whether or not that is
+      # actually an ancestor of the class.
+      #
+      # Mainly for internal use.
+      def active_record_super #:nodoc:
+        if self == Base || superclass && superclass < Model::Tag
+          superclass
+        else
+          Base
+        end
+      end
+
       protected
 
       # Returns the class descending directly from ActiveRecord::Base or an
@@ -90,12 +104,11 @@ module ActiveRecord
           raise ActiveRecordError, "#{name} doesn't belong in a hierarchy descending from ActiveRecord"
         end
 
-        if klass == Base || klass.superclass == Base ||
-           klass.superclass < Model::Tag && klass.superclass.abstract_class? ||
-           !(klass.superclass < Model::Tag)
+        sup = klass.active_record_super
+        if klass == Base || sup == Base || sup.abstract_class?
           klass
         else
-          class_of_active_record_descendant(klass.superclass)
+          class_of_active_record_descendant(sup)
         end
       end
 

activerecord/lib/active_record/model_schema.rb

@@ -128,10 +128,10 @@ module ActiveRecord
 
       # Computes the table name, (re)sets it internally, and returns it.
       def reset_table_name #:nodoc:
-        if (superclass < ActiveRecord::Model) && superclass.abstract_class?
-          self.table_name = superclass.table_name || compute_table_name
+        if active_record_super.abstract_class?
+          self.table_name = active_record_super.table_name || compute_table_name
         elsif abstract_class?
-          self.table_name = superclass == Base ? nil : superclass.table_name
+          self.table_name = active_record_super == Base ? nil : active_record_super.table_name
         else
           self.table_name = compute_table_name
         end
@@ -143,10 +143,10 @@ module ActiveRecord
 
       # The name of the column containing the object's class when Single Table Inheritance is used
       def inheritance_column
-        if self == Base || !(superclass < Model)
+        if self == Base
           'type'
         else
-          (@inheritance_column ||= nil) || superclass.inheritance_column
+          (@inheritance_column ||= nil) || active_record_super.inheritance_column
         end
       end
 

activerecord/test/cases/attribute_methods/read_test.rb

@@ -15,6 +15,7 @@ module ActiveRecord
       def setup
         @klass = Class.new do
           def self.superclass; Base; end
+          def self.active_record_super; Base; end
           def self.base_class; self; end
 
           include ActiveRecord::AttributeMethods

activerecord/test/cases/connection_adapters/connection_handler_test.rb

@@ -8,6 +8,9 @@ module ActiveRecord
         @handler.establish_connection 'america', Base.connection_pool.spec
         @klass = Class.new do
           def self.name; 'america'; end
+          class << self
+            alias active_record_super superclass
+          end
         end
         @subklass = Class.new(@klass) do
           def self.name; 'north america'; end