bugdown: Raise BugdownRenderingException.

We now raise an exception in bugdown.do_convert() if rendering
fails, to avoid silent failures, and then calling code can convert
the exception to a JsonableError.

zerver/lib/actions.py

@@ -9,6 +9,7 @@ from django.utils.translation import ugettext as _
 from django.conf import settings
 from django.core import validators
 from django.contrib.sessions.models import Session
+from zerver.lib.bugdown import BugdownRenderingException
 from zerver.lib.cache import flush_user_profile
 from zerver.lib.context_managers import lockfile
 from zerver.models import Realm, RealmEmoji, Stream, UserProfile, UserActivity, \
@@ -1064,7 +1065,9 @@ def check_message(sender, client, message_type_name, message_to,
         message.pub_date = timezone.now()
     message.sending_client = client
 
-    if not message.maybe_render_content(realm.domain):
+    try:
+        message.maybe_render_content(realm.domain)
+    except BugdownRenderingException:
         raise JsonableError(_("Unable to render message"))
 
     if client.name == "zephyr_mirror":

zerver/lib/bugdown/__init__.py

@@ -57,6 +57,9 @@ if False:
     # mypy requires the Optional to be inside Union
     ElementStringNone = Union[Element, Optional[text_type]]
 
+class BugdownRenderingException(Exception):
+    pass
+
 def unescape(s):
     # type: (text_type) -> (text_type)
     if six.PY2:
@@ -1177,7 +1180,7 @@ def do_convert(md, realm_domain=None, message=None):
         mail.mail_admins(subject, "Failed message: %s\n\n%s\n\n" % (
                                     cleaned, traceback.format_exc()),
                          fail_silently=False)
-        return None
+        raise BugdownRenderingException()
     finally:
         current_message = None
         db_data = None

zerver/tests/test_bugdown.py

@@ -570,8 +570,8 @@ class BugdownErrorTests(ZulipTestCase):
     def test_bugdown_error_handling(self):
         # type: () -> None
         with self.simulated_markdown_failure():
-            rendered_message = bugdown.convert('', 'zulip.com')
+            with self.assertRaises(bugdown.BugdownRenderingException):
-            self.assertEqual(rendered_message, None)
+                bugdown.convert('', 'zulip.com')
 
     def test_send_message_errors(self):
         # type: () -> None