Nested simple_form calls no longer lose reference to original error proc.

lib/simple_form/action_view_extensions/form_helper.rb

@@ -9,10 +9,6 @@ module SimpleForm
     #   end
     #
     module FormHelper
-      # based on what is done in formtastic
-      # http://github.com/justinfrench/formtastic/blob/master/lib/formtastic.rb#L1706
-      @@default_field_error_proc = nil
-
       # Override the default ActiveRecordHelper behaviour of wrapping the input.
       # This gets taken care of semantically by adding an error class to the wrapper tag
       # containing the input.
@@ -46,10 +42,10 @@ module SimpleForm
       private
 
       def with_simple_form_field_error_proc
-        @@default_field_error_proc = ::ActionView::Base.field_error_proc
+        default_field_error_proc = ::ActionView::Base.field_error_proc
         ::ActionView::Base.field_error_proc = FIELD_ERROR_PROC
         result = yield
-        ::ActionView::Base.field_error_proc = @@default_field_error_proc
+        ::ActionView::Base.field_error_proc = default_field_error_proc
         result
       end
 

test/action_view_extensions/form_helper_test.rb

@@ -101,4 +101,23 @@ class FormHelperTest < ActionView::TestCase
 
     assert_select "input[name='author[name]'][value='hash backed author']"
   end
+
+  test 'custom error proc is not destructive' do
+    previous_error_proc = ActionView::Base.field_error_proc
+
+    begin
+      expected_error_proc = lambda {}
+      ActionView::Base.field_error_proc = expected_error_proc
+
+      simple_form_for :user do |f|
+        simple_fields_for 'address' do
+        end
+      end
+
+      assert_equal expected_error_proc, ActionView::Base.field_error_proc
+
+    ensure
+      ActionView::Base.field_error_proc = previous_error_proc
+    end
+  end
 end