Fix pre-selected item when using belongs_to

lib/activeadmin/searchable_select/select_input_extension.rb

@@ -84,7 +84,7 @@ def selected_values
       end
 
       def option_collection_scope
-        option_collection.scope(template, ajax_params)
+        option_collection.scope(template, path_params.merge(ajax_params))
       end
 
       def option_collection

spec/features/ajax_params_spec.rb

@@ -50,4 +50,52 @@
     expect(response.body).to have_selector('.searchable-select-input' \
                                            "[data-ajax-url*='#{url_matcher}']")
   end
+
+  context 'when using belongs_to' do
+    before(:each) do
+      ActiveAdminHelpers.setup do
+
+        ActiveAdmin.register(OptionType)
+
+        ActiveAdmin.register(Product) do
+
+        ActiveAdmin.register(OptionValue) do
+          belongs_to :option_type
+          searchable_select_options(scope: lambda do |params|
+                                            OptionValue.where(
+                                              option_type_id: params[:option_type_id]
+                                            )
+                                          end,
+                                    text_attribute: :value)
+        end
+
+        ActiveAdmin.register(Variant) do
+          belongs_to :product
+
+          form do |f|
+            f.input(:option_value,
+                    as: :searchable_select,
+                    ajax: {
+                      resource: OptionValue,
+                      path_params: {
+                        option_type_id: f.object.product.option_type_id
+                      }
+                    })
+          end
+        end
+      end
+    end
+
+    it 'pre-select items in the associations' do 
+      option_type = OptionType.create
+      product = Product.create(option_type: option_type)
+      option_value = OptionValue.create(option_type: option_type, value: 'Red')
+      variant = Variant.create(product: product, option_value: option_value)
+
+      get "/admin/products/#{product.id}/variants/#{variant.id}/edit"
+
+      expect(response.body).to have_selector('.searchable-select-input option[selected]',
+        count: 1)
+    end
+  end
 end