fix default I18n lookup for association input

closes #679

CHANGELOG.md

@@ -6,6 +6,9 @@
     Closes [#576](https://github.com/plataformatec/simple_form/issues/576).
 
 ### bug fix
+  * Fix default I18n lookup for association input.
+  ([@nashby](https://github.com/nashby))
+  Closes [#679](https://github.com/plataformatec/simple_form/issues/679).
   * Fix escaping issue in `label_input` component
   ([@allomov](https://github.com/allomov))
 

lib/simple_form/inputs/base.rb

@@ -174,7 +174,7 @@ module SimpleForm
           lookups << :"#{joined_model_names}.#{reflection_or_attribute_name}"
         end
         lookups << :"defaults.#{lookup_action}.#{reflection_or_attribute_name}"
-        lookups << :"defaults.#{attribute_name}"
+        lookups << :"defaults.#{reflection_or_attribute_name}"
         lookups << default
 
         I18n.t(lookups.shift, :scope => :"simple_form.#{namespace}", :default => lookups).presence

test/form_builder/association_test.rb

@@ -180,4 +180,14 @@ class AssociationTest < ActionView::TestCase
     assert_equal({ :as => :check_boxes, :collection_wrapper_tag => :ul, :item_wrapper_tag => :li},
                  options)
   end
+
+  test 'builder association uses i18n under defaults namespace to lookup translation' do
+    store_translations(:en, :simple_form => {
+      :labels => {:defaults => {:company => 'Plataformatec' } }
+    }) do
+      with_association_for @user, :company, :required => false
+
+      assert_select 'form label', 'Plataformatec'
+    end
+  end
 end