Fix `thread_mattr_accessor` share variable superclass with subclass

The current implementation of `thread_mattr_accessor` set variable
sharing superclass with subclass. So the method doesn't work as documented.

Precondition

    class Account
      thread_mattr_accessor :user
    end

    class Customer < Account
    end

    Account.user = "DHH"
    Account.user  #=> "DHH"
    Customer.user = "Rafael"
    Customer.user # => "Rafael"

Documented behavior

    Account.user  # => "DHH"

Actual behavior

    Account.user  # => "Rafael"

Current implementation set variable statically likes `Thread[:attr_Account_user]`,
and customer also use it.

Make variable name dynamic to use own thread-local variable.

1 files changed, 4 insertions, 4 deletions

diff --git a/activesupport/lib/active_support/core_ext/module/attribute_accessors_per_thread.rb b/activesupport/lib/active_support/core_ext/module/attribute_accessors_per_thread.rb
index 7015333f7c..946be64f1c 100644
--- a/activesupport/lib/active_support/core_ext/module/attribute_accessors_per_thread.rb
+++ b/activesupport/lib/active_support/core_ext/module/attribute_accessors_per_thread.rb
@@ -41,14 +41,14 @@ class Module
       raise NameError.new("invalid attribute name: #{sym}") unless /^[_A-Za-z]\w*$/.match?(sym)
       class_eval(<<-EOS, __FILE__, __LINE__ + 1)
         def self.#{sym}
-          Thread.current[:"attr_#{name}_#{sym}"]
+          Thread.current["attr_"+ name + "_#{sym}"]
         end
       EOS
 
       unless options[:instance_reader] == false || options[:instance_accessor] == false
         class_eval(<<-EOS, __FILE__, __LINE__ + 1)
           def #{sym}
-            Thread.current[:"attr_#{name}_#{sym}"]
+            Thread.current["attr_"+ self.class.name + "_#{sym}"]
           end
         EOS
       end
@@ -80,14 +80,14 @@ class Module
       raise NameError.new("invalid attribute name: #{sym}") unless /^[_A-Za-z]\w*$/.match?(sym)
       class_eval(<<-EOS, __FILE__, __LINE__ + 1)
         def self.#{sym}=(obj)
-          Thread.current[:"attr_#{name}_#{sym}"] = obj
+          Thread.current["attr_"+ name + "_#{sym}"] = obj
         end
       EOS
 
       unless options[:instance_writer] == false || options[:instance_accessor] == false
         class_eval(<<-EOS, __FILE__, __LINE__ + 1)
           def #{sym}=(obj)
-            Thread.current[:"attr_#{name}_#{sym}"] = obj
+            Thread.current["attr_"+ self.class.name + "_#{sym}"] = obj
           end
         EOS
       end