Display more specific invalid_voucher message to customer

It was implemented with error code  409 in https://github.com/openfoodfoundation/vine/pull/112

app/controllers/voucher_adjustments_controller.rb

@@ -90,11 +90,13 @@ class VoucherAdjustmentsController < BaseController
       voucher_code: voucher_params[:voucher_code], enterprise: @order.distributor
     )
     voucher = vine_voucher_validator.validate
+    errors = vine_voucher_validator.errors
 
-    return nil if vine_voucher_validator.errors[:not_found_voucher].present?
+    return nil if errors[:not_found_voucher].present?
 
-    if vine_voucher_validator.errors.present?
-      @order.errors.add(:voucher_code, I18n.t('checkout.errors.add_voucher_error'))
+    if errors.present?
+      message = errors[:invalid_voucher] || I18n.t('checkout.errors.add_voucher_error')
+      @order.errors.add(:voucher_code, message)
       return nil
     end
 

app/services/vine/voucher_validator_service.rb

@@ -47,7 +47,7 @@ module Vine
     end
 
     def handle_errors(response)
-      if response[:status] == 400
+      if [400, 409].include?(response[:status])
         message = response[:body] && JSON.parse(response[:body]).dig("meta", "message")
         key = VINE_ERRORS.fetch(message, :invalid_voucher)
         errors[:invalid_voucher] = I18n.t("vine_voucher_validator_service.errors.#{key}")

spec/requests/voucher_adjustments_spec.rb

@@ -161,7 +161,19 @@ RSpec.describe VoucherAdjustmentsController do
             post("/voucher_adjustments", params:)
 
             expect(response).to be_unprocessable
-            expect(flash[:error]).to match "There was an error while adding the voucher"
+            expect(flash[:error]).to match "The voucher is not valid"
+          end
+        end
+
+        context "when voucher has expired" do
+          it "returns 422 and an error message" do
+            mock_vine_voucher_validator(voucher: nil,
+                                        errors: { invalid_voucher: "The voucher has expired" })
+
+            post("/voucher_adjustments", params:)
+
+            expect(response).to be_unprocessable
+            expect(flash[:error]).to match "The voucher has expired"
           end
         end
 
@@ -219,6 +231,20 @@ RSpec.describe VoucherAdjustmentsController do
             )
           end
         end
+
+        context "when voucher has expired" do
+          it "returns 422 and an error message" do
+            vine_voucher = build(:vine_voucher, code: vine_voucher_code,
+                                                enterprise: distributor)
+            mock_vine_voucher_validator(voucher: vine_voucher,
+                                        errors: { invalid_voucher: "The voucher has expired" })
+
+            post("/voucher_adjustments", params:)
+
+            expect(response).to be_unprocessable
+            expect(flash[:error]).to match "The voucher has expired"
+          end
+        end
       end
     end
   end

spec/services/vine/voucher_validator_service_spec.rb

@@ -448,7 +448,7 @@ RSpec.describe Vine::VoucherValidatorService, feature: :connected_apps do
         }
 
         it "adds a specific error message" do
-          mock_api_exception(type: Faraday::BadRequestError, status: 400, body: data)
+          mock_api_exception(type: Faraday::BadRequestError, status: 409, body: data)
 
           validate_voucher_service.validate
 

spec/system/consumer/checkout/payment_spec.rb

@@ -198,7 +198,7 @@ RSpec.describe "As a consumer, I want to checkout my order" do
                   fill_in "Enter voucher code", with: "KM1891"
                   click_button("Apply")
 
-                  expect(page).to have_content("There was an error while adding the voucher")
+                  expect(page).to have_content("The voucher is not valid")
                   expect(Vouchers::Vine.find_by(code: "KM1891", enterprise: distributor)).to be_nil
                 end
               end