Fix race condition in subscription creation webhooks

Author: spalmurray

billing/tests/test_views.py

@@ -1150,29 +1150,51 @@ def test_subscription_schedule_updated_logs_changes_to_schedule(
         assert self.owner.plan == original_plan
         assert self.owner.plan_user_count == original_quantity
 
-    def test_checkout_session_completed_sets_stripe_customer_id(self):
+    def test_checkout_session_completed_sets_stripe_ids(self):
         self.owner.stripe_customer_id = None
         self.owner.save()
 
-        expected_id = "fhjtwoo40"
+        expected_customer_id = "cus_1234"
+        expected_subscription_id = "sub_7890"
 
         self._send_event(
             payload={
                 "type": "checkout.session.completed",
                 "data": {
                     "object": {
-                        "customer": expected_id,
+                        "customer": expected_customer_id,
                         "client_reference_id": str(self.owner.ownerid),
+                        "subscription": expected_subscription_id,
                     }
                 },
             }
         )
 
         self.owner.refresh_from_db()
-        assert self.owner.stripe_customer_id == expected_id
+        assert self.owner.stripe_customer_id == expected_customer_id
+        assert self.owner.stripe_subscription_id == expected_subscription_id
 
     @patch("billing.views.stripe.Subscription.modify")
     def test_customer_update_but_not_payment_method(self, subscription_modify_mock):
+        payment_method = "pm_123"
+        self._send_event(
+            payload={
+                "type": "customer.updated",
+                "data": {
+                    "object": {
+                        "invoice_settings": {"default_payment_method": None},
+                        "subscriptions": {
+                            "data": [{"default_payment_method": payment_method}]
+                        },
+                    }
+                },
+            }
+        )
+
+        subscription_modify_mock.assert_not_called()
+
+    @patch("billing.views.stripe.Subscription.modify")
+    def test_customer_update_but_payment_method_is_same(self, subscription_modify_mock):
         payment_method = "pm_123"
         self._send_event(
             payload={

billing/views.py

@@ -376,6 +376,10 @@ def customer_updated(self, customer: stripe.Customer) -> None:
         new_default_payment_method = customer["invoice_settings"][
             "default_payment_method"
         ]
+
+        if new_default_payment_method is None:
+            return
+
         for subscription in customer.get("subscriptions", {}).get("data", []):
             if new_default_payment_method == subscription["default_payment_method"]:
                 continue
@@ -401,6 +405,7 @@ def checkout_session_completed(
         )
         owner = Owner.objects.get(ownerid=checkout_session.client_reference_id)
         owner.stripe_customer_id = checkout_session.customer
+        owner.stripe_subscription_id = checkout_session.subscription
         owner.save()
 
         self._log_updated([owner])