stripe: Move error handling into stripe.py too.

This completes the separation of our logic for managing Stripe
customers from the view code for the billing page.

As we add more features to our Customer model and to our Stripe
integration, we might further separate those two things; but for now
they're nearly synonymous and there's no problem in them being mixed
together.

zilencer/lib/stripe.py

@@ -1,12 +1,13 @@
-
+from functools import wraps
 import logging
 import os
+from typing import Any, Callable, TypeVar
 
 from django.conf import settings
+from django.utils.translation import ugettext as _
 import stripe
-from stripe.error import CardError, RateLimitError, InvalidRequestError, \
-    AuthenticationError, APIConnectionError, StripeError
 
+from zerver.lib.exceptions import JsonableError
 from zerver.lib.logging_util import log_to_file
 from zerver.models import Realm, UserProfile
 from zilencer.models import Customer
@@ -24,6 +25,35 @@ billing_logger = logging.getLogger('zilencer.stripe')
 log_to_file(billing_logger, BILLING_LOG_PATH)
 log_to_file(logging.getLogger('stripe'), BILLING_LOG_PATH)
 
+CallableT = TypeVar('CallableT', bound=Callable[..., Any])
+
+class StripeError(JsonableError):
+    pass
+
+def catch_stripe_errors(func: CallableT) -> CallableT:
+    @wraps(func)
+    def wrapped(*args: Any, **kwargs: Any) -> Any:
+        if STRIPE_PUBLISHABLE_KEY is None:
+            # Dev-only message; no translation needed.
+            raise StripeError(
+                "Missing Stripe config. In dev, add to zproject/dev-secrets.conf .")
+        try:
+            return func(*args, **kwargs)
+        except stripe.error.StripeError as e:
+            billing_logger.error("Stripe error: %d %s",
+                                 e.http_status, e.__class__.__name__)
+            if isinstance(e, stripe.error.CardError):
+                raise StripeError(e.json_body.get('error', {}).get('message'))
+            else:
+                raise StripeError(
+                    _("Something went wrong. Please try again or email us at %s.")
+                    % (settings.ZULIP_ADMINISTRATOR,))
+        except Exception as e:
+            billing_logger.exception("Uncaught error in Stripe integration")
+            raise
+    return wrapped  # type: ignore # https://github.com/python/mypy/issues/1927
+
+@catch_stripe_errors
 def count_stripe_cards(realm: Realm) -> int:
     try:
         customer_obj = Customer.objects.get(realm=realm)
@@ -32,6 +62,7 @@ def count_stripe_cards(realm: Realm) -> int:
     except Customer.DoesNotExist:
         return 0
 
+@catch_stripe_errors
 def save_stripe_token(user: UserProfile, token: str) -> int:
     """Returns total number of cards."""
     # The card metadata doesn't show up in Dashboard but can be accessed

zilencer/views.py

@@ -19,7 +19,7 @@ from zerver.lib.validator import check_int
 from zerver.models import UserProfile, Realm
 from zerver.views.push_notifications import validate_token
 from zilencer.lib.stripe import STRIPE_PUBLISHABLE_KEY, count_stripe_cards, \
-    save_stripe_token, CardError, StripeError, billing_logger
+    save_stripe_token, StripeError
 from zilencer.models import RemotePushDeviceToken, RemoteZulipServer
 
 def validate_entity(entity: Union[UserProfile, RemoteZulipServer]) -> None:
@@ -112,16 +112,11 @@ def add_payment_method(request: HttpRequest) -> HttpResponse:
         "email": user.email,
     }  # type: Dict[str, Any]
 
-    def render_error(message: str) -> HttpResponse:
-        ctx["error_message"] = message
-        return render(request, 'zilencer/billing.html', context=ctx)
-
     if not user.is_realm_admin:
-        return render_error(_("You should be an administrator of the organization %s to view this page.")
+        ctx["error_message"] = (
+            _("You should be an administrator of the organization %s to view this page.")
             % (user.realm.name,))
-    if STRIPE_PUBLISHABLE_KEY is None:
+        return render(request, 'zilencer/billing.html', context=ctx)
-        # Dev-only message; no translation needed.
-        return render_error("Missing Stripe config. In dev, add to zproject/dev-secrets.conf .")
 
     try:
         if request.method == "GET":
@@ -133,12 +128,5 @@ def add_payment_method(request: HttpRequest) -> HttpResponse:
             ctx["payment_method_added"] = True
             return render(request, 'zilencer/billing.html', context=ctx)
     except StripeError as e:
-        billing_logger.error("Stripe error: %d %s", e.http_status, e.__class__.__name__)
+        ctx["error_message"] = e.msg
-        if isinstance(e, CardError):
+        return render(request, 'zilencer/billing.html', context=ctx)
-            return render_error(e.json_body.get('error', {}).get('message'))
-        else:
-            return render_error(_("Something went wrong. Please try again or email us at %s.")
-                                % (settings.ZULIP_ADMINISTRATOR,))
-    except Exception as e:
-        billing_logger.exception("Uncaught error in billing")
-        raise