digest: Switch loop to early-abort for clarity.

zerver/lib/digest.py

@@ -3,7 +3,7 @@ import functools
 import heapq
 import logging
 from collections import defaultdict
-from typing import Any, Collection, Dict, List, Set, Tuple
+from typing import Any, Collection, Dict, Iterator, List, Optional, Set, Tuple
 
 from django.conf import settings
 from django.db import transaction
@@ -383,9 +383,12 @@ def bulk_handle_digest_email(user_ids: List[int], cutoff: float) -> None:
         context = context_map[user.id]
 
         # We don't want to send emails containing almost no information.
-        if enough_traffic(context["hot_conversations"], context["new_streams_count"]):
+        if not enough_traffic(context["hot_conversations"], context["new_streams_count"]):
+            continue
+
         digest_users.append(user)
         logger.info("Sending digest email for user %s", user.id)
+
         # Send now, as a ScheduledEmail
         send_future_email(
             "zerver/emails/digest",

zerver/tests/test_digest.py

@@ -136,6 +136,23 @@ class TestDigestEmailMessages(ZulipTestCase):
             set(emailed_user_ids), {user_id for user_id in user_ids if user_id != hamlet.id}
         )
 
+    @mock.patch("zerver.lib.digest.send_future_email")
+    def test_enough_traffic(self, mock_send_future_email: mock.MagicMock) -> None:
+        othello = self.example_user("othello")
+        self.subscribe(othello, "Verona")
+
+        in_the_future = timezone_now().timestamp() + 60
+
+        bulk_handle_digest_email([othello.id], in_the_future)
+        mock_send_future_email.assert_not_called()
+
+        with mock.patch(
+            "zerver.lib.digest.enough_traffic", return_value=True
+        ) as enough_traffic_mock:
+            bulk_handle_digest_email([othello.id], in_the_future)
+            mock_send_future_email.assert_called()
+            enough_traffic_mock.assert_called_once_with([], 0)
+
     @mock.patch("zerver.lib.digest.enough_traffic")
     @mock.patch("zerver.lib.digest.send_future_email")
     def test_guest_user_multiple_stream_sender(