PPv2 APM: Create referenced PPObjects for APM Orders; enable webhooks to capture them (#3958)

src/pretix/plugins/paypal2/payment.py

@@ -30,6 +30,7 @@ from django import forms
 from django.conf import settings
 from django.contrib import messages
 from django.core.cache import cache
+from django.db import transaction
 from django.http import HttpRequest
 from django.template.loader import get_template
 from django.templatetags.static import static
@@ -54,6 +55,7 @@ from pretix.base.models import Event, Order, OrderPayment, OrderRefund, Quota
 from pretix.base.payment import BasePaymentProvider, PaymentException
 from pretix.base.services.mail import SendMailException
 from pretix.base.settings import SettingsSandbox
+from pretix.helpers import OF_SELF
 from pretix.helpers.urls import build_absolute_uri as build_global_uri
 from pretix.multidomain.urlreverse import build_absolute_uri, eventreverse
 from pretix.plugins.paypal2.client.core.environment import (
@@ -585,6 +587,9 @@ class PaypalMethod(BasePaymentProvider):
                 },
             })
             response = self.client.execute(paymentreq)
+
+            if payment:
+                ReferencedPayPalObject.objects.get_or_create(order=payment.order, payment=payment, reference=response.result.id)
         except IOError as e:
             if "RESOURCE_NOT_FOUND" in str(e):
                 messages.error(request, _('Your payment has failed due to a known issue within PayPal. Please try '
@@ -617,7 +622,13 @@ class PaypalMethod(BasePaymentProvider):
         }
         return template.render(ctx)
 
+    @transaction.atomic
     def execute_payment(self, request: HttpRequest, payment: OrderPayment):
+        payment = OrderPayment.objects.select_for_update(of=OF_SELF).get(pk=payment.pk)
+        if payment.state == OrderPayment.PAYMENT_STATE_CONFIRMED:
+            logger.warning('payment is already confirmed; possible return-view/webhook race-condition')
+            return
+
         try:
             if request.session.get('payment_paypal_oid', '') == '':
                 raise PaymentException(_('We were unable to process your payment. See below for details on how to '