Don't share attribute matchers between classes [#3216 state:resolved]

Allows separate models that include ActiveModel::AttributeMethods to
use different sets of attribute matchers.

Signed-off-by: Joshua Peek <josh@joshpeek.com>

activemodel/lib/active_model/attribute_methods.rb

@@ -1,3 +1,6 @@
+require 'active_support/core_ext/hash/keys'
+require 'active_support/core_ext/class/inheritable_attributes'
+
 module ActiveModel
   class MissingAttributeError < NoMethodError
   end
@@ -219,7 +222,7 @@ module ActiveModel
         end
 
         def attribute_method_matchers #:nodoc:
-          @@attribute_method_matchers ||= []
+          read_inheritable_attribute(:attribute_method_matchers) || write_inheritable_attribute(:attribute_method_matchers, [])
         end
     end
 

activemodel/test/cases/attribute_methods_test.rb

@@ -0,0 +1,20 @@
+require 'cases/helper'
+
+class ModelWithAttributes
+  include ActiveModel::AttributeMethods
+  
+  attribute_method_suffix ''
+end
+
+class ModelWithAttributes2
+  include ActiveModel::AttributeMethods
+  
+  attribute_method_suffix '_test'
+end
+
+class AttributeMethodsTest < ActiveModel::TestCase
+  test 'unrelated classes should not share attribute method matchers' do
+    assert_not_equal ModelWithAttributes.send(:attribute_method_matchers),
+                     ModelWithAttributes2.send(:attribute_method_matchers)
+  end
+end