internal_prep_message: Make realm argument mandatory.

In order to correctly handle messages sent by cross-realm bots, we
need to specify the realm that the messages are being sent into in the
send message code path.  The commit and its successors convert that
code path to include the realm the message is being sent to explicitly.

zerver/lib/actions.py

@@ -1247,7 +1247,7 @@ def send_pm_if_empty_stream(sender, stream, stream_name, realm):
                "tried to send a message to stream `%s`, but %s"
                "click the gear in the left-side stream list." %
                (sender.full_name, stream_name, error_msg))
-    message = internal_prep_message(settings.NOTIFICATION_BOT, "private",
+    message = internal_prep_message(realm, settings.NOTIFICATION_BOT, "private",
                                     sender.bot_owner.email, "", content)
     do_send_messages([message])
 
@@ -1351,9 +1351,9 @@ def check_message(sender, client, message_type_name, message_to,
 
     return {'message': message, 'stream': stream, 'local_id': local_id, 'sender_queue_id': sender_queue_id}
 
-def internal_prep_message(sender_email, recipient_type_name, recipients,
-                          subject, content, realm=None):
-    # type: (Text, str, Text, Text, Text, Optional[Realm]) -> Optional[Dict[str, Any]]
+def internal_prep_message(realm, sender_email, recipient_type_name, recipients,
+                          subject, content):
+    # type: (Realm, Text, str, Text, Text, Text) -> Optional[Dict[str, Any]]
     """
     Create a message object and checks it, but doesn't send it or save it to the database.
     The internal function that calls this can therefore batch send a bunch of created
@@ -1365,7 +1365,7 @@ def internal_prep_message(sender_email, recipient_type_name, recipients,
 
     sender = get_user_profile_by_email(sender_email)
     if realm is None:
-        realm = sender.realm
+        raise RuntimeError("None is not a valid realm for internal_prep_message!")
     parsed_recipients = extract_recipients(recipients)
     if recipient_type_name == "stream":
         stream, _ = create_stream_if_needed(realm, parsed_recipients[0])
@@ -1381,8 +1381,8 @@ def internal_prep_message(sender_email, recipient_type_name, recipients,
 def internal_send_message(sender_email, recipient_type_name, recipients,
                           subject, content, realm=None):
     # type: (Text, str, Text, Text, Text, Optional[Realm]) -> None
-    msg = internal_prep_message(sender_email, recipient_type_name, recipients,
-                                subject, content, realm)
+    msg = internal_prep_message(realm, sender_email, recipient_type_name, recipients,
+                                subject, content)
 
     # internal_prep_message encountered an error
     if msg is None:
@@ -2167,9 +2167,9 @@ def do_create_realm(string_id, name, restricted_to_domain=None,
 
 This is a message on stream `%s` with the topic `welcome`. We'll use this stream for
 system-generated notifications.""" % (product_name, notifications_stream.name,)
-        msg = internal_prep_message(settings.WELCOME_BOT, 'stream',
+        msg = internal_prep_message(realm, settings.WELCOME_BOT, 'stream',
                                     notifications_stream.name, "welcome",
-                                    content, realm=realm)
+                                    content)
         do_send_messages([msg])
 
         # Log the event

zerver/views/streams.py

@@ -369,7 +369,8 @@ def add_subscriptions_backend(request, user_profile,
 
             if len([s for s in subscriptions if not private_streams[s]]) > 0:
                 msg += "\nYou can see historical content on a non-invite-only stream by narrowing to it."
-            notifications.append(internal_prep_message(settings.NOTIFICATION_BOT,
+            notifications.append(internal_prep_message(
+                user_profile.realm, settings.NOTIFICATION_BOT,
                 "private", email, "", msg))
 
     if announce and len(created_streams) > 0:
@@ -381,10 +382,9 @@ def add_subscriptions_backend(request, user_profile,
                 stream_msg = "a new stream #**%s**." % created_streams[0].name
             msg = ("%s just created %s" % (user_profile.full_name, stream_msg))
             notifications.append(
-                internal_prep_message(settings.NOTIFICATION_BOT,
+                internal_prep_message(user_profile.realm, settings.NOTIFICATION_BOT,
                                       "stream",
-                                      notifications_stream.name, "Streams", msg,
-                                      realm=notifications_stream.realm))
+                                      notifications_stream.name, "Streams", msg))
         else:
             msg = ("Hi there!  %s just created a new stream #**%s**."
                    % (user_profile.full_name, created_streams[0].name))
@@ -393,7 +393,8 @@ def add_subscriptions_backend(request, user_profile,
                 # (who will get the notification above instead).
                 if realm_user_dict['email'] in principals or realm_user_dict['email'] == user_profile.email:
                     continue
-                notifications.append(internal_prep_message(settings.NOTIFICATION_BOT,
+                notifications.append(internal_prep_message(
+                    user_profile.realm, settings.NOTIFICATION_BOT,
                     "private",
                     realm_user_dict['email'], "", msg))