Fix table_name in ActiveRecord with more than one abstract ancestors

When subclassing abstract_class table_name should be always computed
based on class name, no matter if superclass is subclassing base
or another abstract_class. So:

class FirstAbstract < ActiveRecord::Base
  self.abstract_class = true
end
class SecondAbstract < FirstAbstract
  self.abstract_class = true
end

class Post < SecondAbstract
  self.table_name #=> 'posts' (not 'second_abstracts')
end

1 files changed, 7 insertions, 3 deletions

diff --git a/activerecord/lib/active_record/model_schema.rb b/activerecord/lib/active_record/model_schema.rb
index 36417d89f7..0e8c2c09ce 100644
--- a/activerecord/lib/active_record/model_schema.rb
+++ b/activerecord/lib/active_record/model_schema.rb
@@ -139,10 +139,14 @@ module ActiveRecord
 
       # Computes the table name, (re)sets it internally, and returns it.
       def reset_table_name #:nodoc:
-        if superclass.abstract_class?
+        if abstract_class?
+          self.table_name = if superclass == Base || superclass.abstract_class?
+                              nil
+                            else
+                              superclass.table_name
+                            end
+        elsif superclass.abstract_class?
           self.table_name = superclass.table_name || compute_table_name
-        elsif abstract_class?
-          self.table_name = superclass == Base ? nil : superclass.table_name
         else
           self.table_name = compute_table_name
         end