fix: coupon/redeem URL redirects user to legacy checkout when a vouch…

…er is invalid

ecommerce/coupons/tests/test_views.py

@@ -441,10 +441,16 @@ def test_sku_not_provided(self):
     def test_invalid_voucher_code(self):
         """ Verify an error is returned when voucher does not exist. """
         code = FuzzyText().fuzz().upper()
+        expected_message = 'No voucher found with code {code}'.format(code=code)
         url = format_url(base=self.redeem_url, params={'code': code, 'sku': self.stock_record.partner_sku})
-        response = self.client.get(url)
-        msg = 'No voucher found with code {code}'.format(code=code)
-        self.assertEqual(response.context['error'], msg)
+        response = self.client.get(url, follow=True)
+
+        messages = []
+        messages += response.context['messages']
+
+        self.assertEqual(messages[0].tags, 'error')
+        self.assertEqual(messages[0].message, expected_message)
+        self.assert_redemption_page_redirects(self.get_coupon_redeem_success_expected_redirect_url())
 
     def test_no_product(self):
         """ Verify an error is returned when a stock record for the provided SKU doesn't exist. """

ecommerce/coupons/views.py

@@ -169,16 +169,26 @@ def get(self, request):  # pylint: disable=too-many-statements
         if not sku:
             return render(request, template_name, {'error': _('SKU not provided.')})
 
+        try:
+            product = StockRecord.objects.get(partner_sku=sku).product
+        except StockRecord.DoesNotExist:
+            return render(request, template_name, {'error': _('The product does not exist.')})
+
         try:
             voucher = Voucher.objects.get(code=code)
         except Voucher.DoesNotExist:
+            try:
+                basket = prepare_basket(request, [product])
+            except AlreadyPlacedOrderException:
+                msg = _('You have already purchased {course} seat.').format(course=product.course.name)
+                return render(request, template_name, {'error': msg})
+
             msg = 'No voucher found with code {code}'.format(code=code)
-            return render(request, template_name, {'error': _(msg)})
+            messages.error(self.request, _(msg))
 
-        try:
-            product = StockRecord.objects.get(partner_sku=sku).product
-        except StockRecord.DoesNotExist:
-            return render(request, template_name, {'error': _('The product does not exist.')})
+            redirect_url = get_payment_microfrontend_or_basket_url(self.request) + "?coupon_redeem_redirect=1"
+            redirect_url = add_stripe_flag_to_url(redirect_url, self.request)
+            return HttpResponseRedirect(redirect_url)
 
         valid_voucher, msg, hide_error_message = voucher_is_valid(voucher, [product], request)
         if not valid_voucher: