FIX: One-time purchase pending invoice item (#210)

This change ensures we attach the invoice item to the invoice to avoid
any occurrences of an empty invoice being paid with pending invoice
items.

app/controllers/discourse_subscriptions/subscribe_controller.rb

@@ -100,16 +100,22 @@ module DiscourseSubscriptions
         else
           coupon_id = promo_code[:coupon][:id] if promo_code && promo_code[:coupon] &&
             promo_code[:coupon][:id]
+          invoice = ::Stripe::Invoice.create(customer: customer[:id])
           invoice_item =
             ::Stripe::InvoiceItem.create(
               customer: customer[:id],
               price: params[:plan],
               discounts: [{ coupon: coupon_id }],
+              invoice: invoice[:id],
             )
-          invoice = ::Stripe::Invoice.create(customer: customer[:id])
           transaction = ::Stripe::Invoice.finalize_invoice(invoice[:id])
           payment_intent = retrieve_payment_intent(transaction[:id]) if transaction[:status] ==
             "open"
+          if payment_intent.nil?
+            return(
+              render_json_error I18n.t("js.discourse_subscriptions.subscribe.transaction_error")
+            )
+          end
           transaction = ::Stripe::Invoice.pay(invoice[:id]) if payment_intent[:status] ==
             "successful"
         end

app/controllers/discourse_subscriptions/user/payments_controller.rb

@@ -45,8 +45,10 @@ module DiscourseSubscriptions
         invoices_with_products =
           all_invoices[:data].select do |invoice|
             invoice_lines = invoice[:lines][:data][0] if invoice[:lines] && invoice[:lines][:data]
-            invoice_product_id = parse_invoice_lines(invoice_lines)
-            product_ids.include?(invoice_product_id)
+            if invoice_lines
+              invoice_product_id = parse_invoice_lines(invoice_lines)
+              product_ids.include?(invoice_product_id)
+            end
           end
       end
 

spec/requests/subscribe_controller_spec.rb

@@ -266,6 +266,35 @@ RSpec.describe DiscourseSubscriptions::SubscribeController do
           }.to change { DiscourseSubscriptions::Customer.count }
         end
 
+        it "returns 422 on a one time payment subscription error" do
+          # It's possible that the invoice item doesn't get attached
+          # to the invoice. This means the invoice is paid, but for $0.00 with
+          # a pending invoice item.
+          ::Stripe::Price.expects(:retrieve).returns(
+            type: "one_time",
+            product: "product_12345",
+            metadata: {
+              group_name: "awesome",
+            },
+          )
+
+          ::Stripe::InvoiceItem.expects(:create)
+
+          ::Stripe::Invoice.expects(:create).returns(status: "open", id: "in_123")
+
+          ::Stripe::Invoice.expects(:finalize_invoice).returns(
+            id: "in_123",
+            status: "paid",
+            payment_intent: "pi_123",
+          )
+
+          expect {
+            post "/s/create.json", params: { plan: "plan_1234", source: "tok_1234" }
+          }.not_to change { DiscourseSubscriptions::Customer.count }
+
+          expect(response.status).to eq 422
+        end
+
         it "creates a one time payment subscription" do
           ::Stripe::Price.expects(:retrieve).returns(
             type: "one_time",
@@ -414,14 +443,15 @@ RSpec.describe DiscourseSubscriptions::SubscribeController do
                 },
               )
 
+              ::Stripe::Invoice.expects(:create).returns(status: "open", id: "in_123")
+
               ::Stripe::InvoiceItem.expects(:create).with(
                 customer: "cus_1234",
                 price: "plan_1234",
                 discounts: [{ coupon: "c123" }],
+                invoice: "in_123",
               )
 
-              ::Stripe::Invoice.expects(:create).returns(status: "open", id: "in_123")
-
               ::Stripe::Invoice.expects(:finalize_invoice).returns(
                 id: "in_123",
                 status: "open",