emails: Added placeholders strings in FormAddress.

We've had a bug for a while that if any ScheduledEmail objects get
created with the wrong email sender address, even after the sysadmin
corrects the problem, they'll still get errors because of the objects
stored with the wrong format.

We solve this by using FromAddress placeholders strings in
send_future_email function, so that ScheduledEmail objects end up
setting the final `from_address` value when mail is actually sent
using the setting in effect at that time.

Fixes #11008.

zerver/lib/digest.py

@@ -212,7 +212,8 @@ def handle_digest_email(user_profile_id: int, cutoff: float,
         logger.info("Sending digest email for user %s" % (user_profile.id,))
         # Send now, as a ScheduledEmail
         send_future_email('zerver/emails/digest', user_profile.realm, to_user_ids=[user_profile.id],
-                          from_name="Zulip Digest", from_address=FromAddress.NOREPLY, context=context)
+                          from_name="Zulip Digest", from_address=FromAddress.no_reply_placeholder,
+                          context=context)
     return None
 
 def exclude_subscription_modified_streams(user_profile: UserProfile,

zerver/lib/email_notifications.py

@@ -546,7 +546,7 @@ def enqueue_welcome_emails(user: UserProfile, realm_creation: bool=False) -> Non
         from_address = settings.WELCOME_EMAIL_SENDER['email']
     else:
         from_name = None
-        from_address = FromAddress.SUPPORT
+        from_address = FromAddress.support_placeholder
 
     other_account_count = UserProfile.objects.filter(
         delivery_email__iexact=user.delivery_email).exclude(id=user.id).count()

zerver/lib/send_email.py

@@ -29,6 +29,10 @@ class FromAddress:
     SUPPORT = parseaddr(settings.ZULIP_ADMINISTRATOR)[1]
     NOREPLY = parseaddr(settings.NOREPLY_EMAIL_ADDRESS)[1]
 
+    support_placeholder = "SUPPORT"
+    no_reply_placeholder = 'NO_REPLY'
+    tokenized_no_reply_placeholder = 'TOKENIZED_NO_REPLY'
+
     # Generates an unpredictable noreply address.
     @staticmethod
     def tokenized_no_reply_address() -> str:
@@ -96,6 +100,13 @@ def build_email(template_prefix: str, to_user_ids: Optional[List[int]]=None,
         from_name = "Zulip"
     if from_address is None:
         from_address = FromAddress.NOREPLY
+    if from_address == FromAddress.tokenized_no_reply_placeholder:
+        from_address = FromAddress.tokenized_no_reply_address()
+    if from_address == FromAddress.no_reply_placeholder:
+        from_address = FromAddress.NOREPLY
+    if from_address == FromAddress.support_placeholder:
+        from_address = FromAddress.SUPPORT
+
     from_email = formataddr((from_name, from_address))
     reply_to = None
     if reply_to_email is not None:

zerver/tests/test_signup.py

@@ -1399,7 +1399,7 @@ so we didn't send them an invitation. We did send invitations to everyone else!"
             email = data["email"]
             send_future_email(
                 "zerver/emails/invitation_reminder", referrer.realm, to_emails=[email],
-                from_address=FromAddress.NOREPLY, context=context)
+                from_address=FromAddress.no_reply_placeholder, context=context)
         email_jobs_to_deliver = ScheduledEmail.objects.filter(
             scheduled_timestamp__lte=timezone_now())
         self.assertEqual(len(email_jobs_to_deliver), 1)
@@ -1414,7 +1414,7 @@ so we didn't send them an invitation. We did send invitations to everyone else!"
             email = data["email"]
             send_future_email(
                 "zerver/emails/invitation_reminder", referrer.realm, to_emails=[email],
-                from_address=FromAddress.NOREPLY, context=context)
+                from_address=FromAddress.no_reply_placeholder, context=context)
 
         email_jobs_to_deliver = ScheduledEmail.objects.filter(
             scheduled_timestamp__lte=timezone_now(), type=ScheduledEmail.INVITATION_REMINDER)

zerver/worker/queue_processors.py

@@ -241,7 +241,7 @@ class ConfirmationEmailWorker(QueueProcessingWorker):
                 "zerver/emails/invitation_reminder",
                 referrer.realm,
                 to_emails=[invitee.email],
-                from_address=FromAddress.tokenized_no_reply_address(),
+                from_address=FromAddress.tokenized_no_reply_placeholder,
                 language=referrer.realm.default_language,
                 context=context,
                 delay=datetime.timedelta(days=settings.INVITATION_LINK_VALIDITY_DAYS - 2))