Fix cache issue with invalid form data

app/controllers/spree/admin/payment_methods_controller.rb

@@ -43,6 +43,7 @@ module Spree
           redirect_to spree.edit_admin_payment_method_path(@payment_method)
         else
           respond_with(@payment_method)
+          clear_preference_cache
         end
       end
 
@@ -184,6 +185,12 @@ module Spree
           params_for_update
         end
       end
+
+      def clear_preference_cache
+        @payment_method.calculator.preferences.each_key do |key|
+          Rails.cache.delete(@payment_method.calculator.preference_cache_key(key))
+        end
+      end
     end
   end
 end

spec/system/admin/payment_method_spec.rb

@@ -349,7 +349,10 @@ describe '
   context "when updating a payment method with invalid data" do
     let(:payment_method) { create(:payment_method, :flat_rate, amount: 10) }
 
+    # Persist preferences to test that when preferred values are not found in the cache,
+    # they are fetched from the database and displayed correctly
     before do
+      Spree::Preferences::Store.instance.persistence = true
       login_as_admin_and_visit spree.edit_admin_payment_method_path payment_method
       fill_in "payment_method_name", with: ""
       fill_in "payment_method_description", with: "Edited description"
@@ -358,6 +361,10 @@ describe '
       click_button 'Update'
     end
 
+    after do
+      Spree::Preferences::Store.instance.persistence = false
+    end
+
     it "displays the number of errors" do
       expect(page).to have_content("3 errors")
     end
@@ -397,5 +404,15 @@ describe '
       expect(page).to have_field "payment_method_description", with: "Edited description"
       expect(page).to have_unchecked_field "payment_method_distributor_ids_#{@distributors[0].id}"
     end
+
+    it 'displays data fetched from the database after navigating away from the page' do
+      click_link 'Back To Payment Methods List'
+      click_link href: /#{spree.edit_admin_payment_method_path(payment_method)}/
+
+      expect(page).to have_field 'Amount', with: '10.0'
+      expect(page).not_to have_field 'payment_method_name', with: ''
+      expect(page).not_to have_field 'payment_method_description', with: 'Edited description'
+      expect(page).not_to have_unchecked_field "payment_method_distributor_ids_#{@distributors[0].id}"
+    end
   end
 end