corporate: Check for no CustomerPlan on Customer instead of Realm.

In ensure_customer_does_not_have_active_plan, we were already going
through the Customer table to get/check for an active CustomerPlan.

Now we directly get/check for an active CustomerPlan with via the
Customer, which allows for reusing this function for Customer
objects without a Realm set.

corporate/lib/stripe.py

@@ -628,14 +628,14 @@ def is_free_trial_offer_enabled() -> bool:
     return settings.FREE_TRIAL_DAYS not in (None, 0)
 
 
-def ensure_realm_does_not_have_active_plan(realm: Realm) -> None:
-    if get_current_plan_by_realm(realm) is not None:
+def ensure_customer_does_not_have_active_plan(customer: Customer) -> None:
+    if get_current_plan_by_customer(customer) is not None:
         # Unlikely race condition from two people upgrading (clicking "Make payment")
         # at exactly the same time. Doesn't fully resolve the race condition, but having
         # a check here reduces the likelihood.
         billing_logger.warning(
             "Upgrade of %s failed because of existing active plan.",
-            realm.string_id,
+            str(customer),
         )
         raise UpgradeWithExistingPlanError
 
@@ -685,7 +685,7 @@ def process_initial_upgrade(
     customer = update_or_create_stripe_customer(user)
     assert customer.stripe_customer_id is not None  # for mypy
     assert customer.realm is not None
-    ensure_realm_does_not_have_active_plan(customer.realm)
+    ensure_customer_does_not_have_active_plan(customer)
     (
         billing_cycle_anchor,
         next_invoice_date,

corporate/lib/stripe_event_handler.py

@@ -8,7 +8,7 @@ from django.conf import settings
 from corporate.lib.stripe import (
     BillingError,
     UpgradeWithExistingPlanError,
-    ensure_realm_does_not_have_active_plan,
+    ensure_customer_does_not_have_active_plan,
     process_initial_upgrade,
     update_or_create_stripe_customer,
 )
@@ -81,7 +81,7 @@ def handle_checkout_session_completed_event(
         Session.UPGRADE_FROM_BILLING_PAGE,
         Session.RETRY_UPGRADE_WITH_ANOTHER_PAYMENT_METHOD,
     ]:
-        ensure_realm_does_not_have_active_plan(user.realm)
+        ensure_customer_does_not_have_active_plan(session.customer)
         update_or_create_stripe_customer(user, payment_method)
         assert session.payment_intent is not None
         session.payment_intent.status = PaymentIntent.PROCESSING
@@ -97,7 +97,7 @@ def handle_checkout_session_completed_event(
         Session.FREE_TRIAL_UPGRADE_FROM_BILLING_PAGE,
         Session.FREE_TRIAL_UPGRADE_FROM_ONBOARDING_PAGE,
     ]:
-        ensure_realm_does_not_have_active_plan(user.realm)
+        ensure_customer_does_not_have_active_plan(session.customer)
         update_or_create_stripe_customer(user, payment_method)
         process_initial_upgrade(
             user,
@@ -136,7 +136,7 @@ def handle_payment_intent_succeeded_event(
         discountable=False,
     )
     try:
-        ensure_realm_does_not_have_active_plan(user.realm)
+        ensure_customer_does_not_have_active_plan(payment_intent.customer)
     except UpgradeWithExistingPlanError as e:
         stripe_invoice = stripe.Invoice.create(
             auto_advance=True,

corporate/tests/test_stripe.py

@@ -624,7 +624,7 @@ class StripeTestCase(ZulipTestCase):
         class StripeMock(Mock):
             def __init__(self, depth: int = 1) -> None:
                 super().__init__(spec=stripe.Card)
-                self.id = "id"
+                self.id = "cus_123"
                 self.created = "1000"
                 self.last4 = "4242"
 
@@ -1894,7 +1894,7 @@ class StripeTest(StripeTestCase):
         )
         self.assertEqual(
             m.output[0],
-            "WARNING:corporate.stripe:Upgrade of zulip failed because of existing active plan.",
+            "WARNING:corporate.stripe:Upgrade of <Realm: zulip 2> (with stripe_customer_id: cus_123) failed because of existing active plan.",
         )
         self.assert_length(m.output, 1)
 
@@ -3247,7 +3247,7 @@ class StripeTest(StripeTestCase):
                 self.local_upgrade(self.seat_count, True, CustomerPlan.ANNUAL, True, False)
         self.assertEqual(
             m.output[0],
-            "WARNING:corporate.stripe:Upgrade of zulip failed because of existing active plan.",
+            "WARNING:corporate.stripe:Upgrade of <Realm: zulip 2> (with stripe_customer_id: cus_123) failed because of existing active plan.",
         )
         self.assertEqual(
             context.exception.error_description, "subscribing with existing subscription"

corporate/views/upgrade.py

@@ -16,7 +16,7 @@ from corporate.lib.stripe import (
     MIN_INVOICED_LICENSES,
     BillingError,
     compute_plan_parameters,
-    ensure_realm_does_not_have_active_plan,
+    ensure_customer_does_not_have_active_plan,
     get_latest_seat_count,
     is_free_trial_offer_enabled,
     is_sponsored_realm,
@@ -169,7 +169,9 @@ def upgrade(
     ),
     licenses: Optional[int] = REQ(json_validator=check_int, default=None),
 ) -> HttpResponse:
-    ensure_realm_does_not_have_active_plan(user.realm)
+    customer = get_customer_by_realm(user.realm)
+    if customer is not None:
+        ensure_customer_does_not_have_active_plan(customer)
     try:
         seat_count = unsign_seat_count(signed_seat_count, salt)
         if billing_modality == "charge_automatically" and license_management == "automatic":
@@ -178,7 +180,6 @@ def upgrade(
             schedule = "annual"
             license_management = "manual"
 
-        customer = get_customer_by_realm(user.realm)
         exempt_from_license_number_check = (
             customer is not None and customer.exempt_from_license_number_check
         )