billing: Raise exceptions instead of returning errors in upgrade flow.

zilencer/lib/stripe.py

@@ -67,6 +67,9 @@ def unsign_string(signed_string: str, salt: str) -> str:
 class StripeError(JsonableError):
     pass
 
+class BillingError(Exception):
+    pass
+
 def catch_stripe_errors(func: CallableT) -> CallableT:
     @wraps(func)
     def wrapped(*args: Any, **kwargs: Any) -> Any:
@@ -147,7 +150,7 @@ def do_subscribe_customer_to_plan(stripe_customer: stripe.Customer, stripe_plan_
         billing_logger.error("Stripe customer %s trying to subscribe to %s, "
                              "but has an active subscription" % (stripe_customer.id, stripe_plan_id))
         # TODO: Change to an error sent to the frontend
-        raise AssertionError("Customer already has an active subscription.")
+        raise BillingError("Your organization has an existing active subscription.")
     stripe_subscription = stripe.Subscription.create(
         customer=stripe_customer.id,
         billing='charge_automatically',
@@ -180,17 +183,17 @@ def do_subscribe_customer_to_plan(stripe_customer: stripe.Customer, stripe_plan_
                 extra_data=ujson.dumps({'quantity': current_seat_count}))
 
 def process_initial_upgrade(user: UserProfile, plan: str, signed_seat_count: str,
-                            salt: str, stripe_token: str) -> Optional[str]:
+                            salt: str, stripe_token: str) -> None:
     if plan not in [Plan.CLOUD_ANNUAL, Plan.CLOUD_MONTHLY]:
         billing_logger.warning("Tampered plan during realm upgrade. user: %s, realm: %s (%s)."
                                % (user.id, user.realm.id, user.realm.string_id))
-        return "Something went wrong. Please contact support@zulipchat.com"
+        raise BillingError("Something went wrong. Please contact support@zulipchat.com")
     try:
         seat_count = int(unsign_string(signed_seat_count, salt))
     except signing.BadSignature:
         billing_logger.warning("Tampered seat count during realm upgrade. user: %s, realm: %s (%s)."
                                % (user.id, user.realm.id, user.realm.string_id))
-        return "Something went wrong. Please contact support@zulipchat.com"
+        raise BillingError("Something went wrong. Please contact support@zulipchat.com")
 
     stripe_customer = do_create_customer_with_payment_source(user, stripe_token)
     do_subscribe_customer_to_plan(
@@ -200,5 +203,3 @@ def process_initial_upgrade(user: UserProfile, plan: str, signed_seat_count: str
         # TODO: billing address details are passed to us in the request;
         # use that to calculate taxes.
         tax_percent=0)
-    # TODO: check for errors and raise/send to frontend
-    return None

zilencer/tests/test_stripe.py

@@ -14,7 +14,8 @@ from zerver.lib.timestamp import timestamp_to_datetime
 from zerver.models import Realm, UserProfile, get_realm, RealmAuditLog
 from zilencer.lib.stripe import StripeError, catch_stripe_errors, \
     do_create_customer_with_payment_source, do_subscribe_customer_to_plan, \
-    get_seat_count, extract_current_subscription, sign_string, unsign_string
+    get_seat_count, extract_current_subscription, sign_string, unsign_string, \
+    BillingError
 from zilencer.models import Customer, Plan
 
 fixture_data_file = open(os.path.join(os.path.dirname(__file__), 'stripe_fixtures.json'), 'r')
@@ -264,7 +265,7 @@ class StripeTest(ZulipTestCase):
 
     @mock.patch("stripe.Customer.retrieve", side_effect=mock_customer_with_active_subscription)
     def test_subscribe_customer_to_second_plan(self, mock_customer_with_active_subscription: mock.Mock) -> None:
-        with self.assertRaisesRegex(AssertionError, "Customer already has an active subscription."):
+        with self.assertRaisesRegex(BillingError, "Your organization has an existing active subscription."):
             do_subscribe_customer_to_plan(stripe.Customer.retrieve(),  # type: ignore # Mocked out function call
                                           self.stripe_plan_id, self.quantity, 0)
 

zilencer/views.py

@@ -26,7 +26,8 @@ from zerver.models import UserProfile, Realm
 from zerver.views.push_notifications import validate_token
 from zilencer.lib.stripe import STRIPE_PUBLISHABLE_KEY, StripeError, \
     get_stripe_customer, get_upcoming_invoice, get_seat_count, \
-    extract_current_subscription, process_initial_upgrade, sign_string
+    extract_current_subscription, process_initial_upgrade, sign_string, \
+    BillingError
 from zilencer.models import RemotePushDeviceToken, RemoteZulipServer, \
     Customer, Plan
 
@@ -169,10 +170,14 @@ def initial_upgrade(request: HttpRequest) -> HttpResponse:
         return HttpResponseRedirect(reverse('zilencer.views.billing_home'))
 
     if request.method == 'POST':
-        error_message = process_initial_upgrade(user, request.POST['plan'],
-                                                request.POST['signed_seat_count'],
-                                                request.POST['salt'], request.POST['stripeToken']) or ""
-        if not error_message:
+        try:
+            process_initial_upgrade(user, request.POST['plan'], request.POST['signed_seat_count'],
+                                    request.POST['salt'], request.POST['stripeToken'])
+        except (BillingError, StripeError) as e:
+            error_message = str(e)
+        except Exception:
+            error_message = "Something went wrong. Please contact support@zulipchat.com."
+        else:
             return HttpResponseRedirect(reverse('zilencer.views.billing_home'))
 
     seat_count = get_seat_count(user.realm)